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  • richardmitnick 10:21 am on January 10, 2021 Permalink | Reply
    Tags: "The Long Decline of Arctic Sea Ice", , , , NASA Earth Observatory   

    From NASA Earth Observatory: “The Long Decline of Arctic Sea Ice” 

    NASA Earth Observatory

    From NASA Earth Observatory

    January 6, 2021
    Kathryn Hansen

    1
    Credit: NASA Earth Observatory.

    Throughout 2020, the Arctic Ocean and surrounding seas endured several notable weather and climate events. In spring, a persistent heatwave over Siberia provoked the rapid melting of sea ice in the East Siberian and Laptev Seas. By the end of summer, Arctic Ocean ice cover melted back to the second-lowest minimum extent on record. In autumn, the annual freeze-up of sea ice got off to a late and sluggish start.

    But any single month, season, or even year, is just a snapshot in time. The long view is more telling, and it is troubling.

    Forty years of satellite data show that 2020 was just the latest in a decades-long decline of Arctic sea ice. In a review of scientific literature [Environmental Research Letters], polar scientists Julienne Stroeve and Dirk Notz outlined some of these changes: In addition to shrinking ice cover, melting seasons are getting longer and sea ice is losing its longevity.

    The longer melting seasons are the result of increasingly earlier starts to spring melting and ever-later starts to freeze-up in autumn. The map above shows trends in the onset of freeze-up from 1979 through 2019. Averaged across the entire Arctic Ocean, freeze-up is happening about a week later per decade. That equates to nearly one month later since the start of the satellite record in 1979.

    The change is part of a cycle called the “ice-albedo feedback.” Open ocean water absorbs 90 percent of the Sun’s energy that falls on it; bright sea ice reflects 80 percent of it. With greater areas of the Arctic Ocean exposed to solar energy early in the season, more heat can be absorbed—a pattern that reinforces melting. Until that heat escapes to the atmosphere, sea ice cannot not regrow.

    2
    Credit: NASA Earth Observatory.

    The chart above demonstrates another way the Arctic is changing: the average age of sea ice is becoming younger. At the start of the satellite record, much of the ice covering the Arctic Ocean was greater than four years old. Today, most of the ice covering the Arctic Ocean is “first-year ice” —ice that forms in winter and does not survive a single summer melt season. (After sea ice reaches its minimum extent each September, the remaining ice graduates to second-year status.)

    Dominated by thin first-year ice, along with some older ice thinned by warm ocean water, the Arctic sea ice pack is becoming more fragile. In summer 2020, ships easily navigated the Northern Sea Route in ice-free waters [Reuters], and even made it to the North Pole without much resistance.

    Fortunately, summers are still not entirely ice-free. “We’ve been hovering for some time around 4 million square kilometers of Arctic sea ice each summer,” said Stroeve, a researcher at University of Manitoba. She added that she intends to examine which conditions and processes could push sea ice to the next “precipitous drop”—when the extent of summer ice cover drops to a new benchmark of 3 million square kilometers.

    References & Resources

    NASA Earth Observatory (2020, December 9) Sluggish Start for Arctic Sea Ice Freeze-Up.
    National Snow & Ice Data Center (2020, December 2) Persistently peculiar Accessed January 5, 2021.
    National Snow & Ice Data Center (2019, November 5) Wild ride in October Accessed January 5, 2021.
    NOAA (2020, December 8) 2020 Arctic Report Card: Climate.gov visual highlights Accessed January 5, 2021.
    Reuters (2020, December 9) Ships Make Record Number of Sailings Through Arctic in 2020 Accessed January 5, 2021.
    Stroeve, J. and Notz, D. (2018) Changing State of Arctic Sea Ice Across all Seasons. Environmental Research Letters 13 (10).

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    The Earth Observatory’s is to share with the public the images, stories, and discoveries about climate and the environment that emerge from NASA research, including its satellite missions, in-the-field research, and climate models. The Earth Observatory staff is supported by the Climate and Radiation Laboratory, and the Hydrospheric and Biospheric Sciences Laboratory located at NASA Goddard Space Flight Center.

     
  • richardmitnick 10:33 am on December 19, 2020 Permalink | Reply
    Tags: "Iceberg Closes In on South Georgia", Antarctic iceberg A-68A has drifted menacingly close to a remote island in the southern Atlantic Ocean., , , NASA Earth Observatory, So far A-68A’s huge size has helped it survive the relatively warm iceberg-killing waters of the South Atlantic that can cut like knives through lesser bergs.   

    From NASA Earth Observatory: “Iceberg Closes In on South Georgia” 

    NASA Earth Observatory

    From NASA Earth Observatory

    December 14, 2020
    Kathryn Hansen

    1
    December 14, 2020

    Antarctic iceberg A-68A has drifted menacingly close to a remote island in the southern Atlantic Ocean.

    Scientists around the world are watching to see what the berg will do next.

    The concern is that the iceberg has approached the edge of the island’s submarine shelf—an area where waters become relatively shallow, measuring less than 200 meters deep. Scientists think the iceberg extends about that far below the water line, meaning it has the potential to snag the seafloor and become “grounded.” Biologists worry about the potential effect a grounded iceberg could have on the island’s wildlife, such as the ability for penguins to access food.

    When we last showed A-68A on November 5, 2020, the enormous block of ice floated about 500 kilometers offshore.

    3
    November 5, 2020
    Iceberg A-68A made headlines in July 2017 when the Delaware-sized block of ice broke from the Larsen C Ice Shelf on the Antarctic Peninsula. The berg has regained the spotlight in austral spring 2020, as it is now drifting toward South Georgia, a remote island in the southern Atlantic Ocean.

    The iceberg and island are both visible in this image, acquired on November 5, 2020, with the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite.

    NASA Terra MODIS schematic.

    NASA/Terra satellite.

    The berg now measures (151 kilometers) 94 miles long and 48 kilometers (30 miles) wide—comparable to the island’s length and width of 167 and 37 kilometers (104 and 23 miles), respectively. It is less than 500 kilometers (300 miles) from the island’s southwest shore.

    In just over three years at sea, Iceberg A-68A has moved generally northward, passing the tip of the Antarctic Peninsula and floating into “Iceberg Alley.” According to David Long, a remote sensing and polar ice scientist at Brigham Young University, more than 90 percent of all Antarctic icebergs are swept along this path from the Weddell Sea toward the South Atlantic Ocean.

    “Most just don’t survive the journey from the Weddell to South Georgia,” Long said. So far, A-68A’s huge size has helped it survive the relatively warm, iceberg-killing waters of the South Atlantic that can cut like knives through lesser bergs.

    Five weeks later, the berg was poised less than 100 kilometers offshore as the Visible Infrared Imaging Radiometer Suite (VIIRS) on the Suomi NPP satellite acquired this natural-color image (above) on December 14.

    NOAA Visible Infrared Imaging Radiometer Suite (VIIRS), on NASA/Suomi NPP satellite.

    NASA/Goddard Suomi NPP satellite.

    3
    December 14, 2020

    The map below shows the path of A-68A, based on data from the Antarctic Iceberg Tracking Database. Long and colleagues created the database in 1999 after tracking a similarly large berg (B-10A).

    4
    September 7, 2017 – November 13, 2020.

    In recent days, a clockwise rotation has appeared to move one end of the berg over the shelf and into shallow waters. Klaus Strübing, a scientist with the International Ice Charting Group (IICWG), thinks the iceberg might already be grounded. He reported that as of December 13, part of the iceberg was in waters just 76 meters deep. Time will tell if A-68A will stall on the shelf, or if the region’s complex ocean currents will carry the berg back out to sea and around the island.

    Strübing has been using radar images from the European Space Agency’s Sentinel-1 satellites to track A-68A since it first broke from Antarctica’s Larsen C Ice Shelf in July 2017. In a paper presented at the 2020 virtual meeting of the IICWG, he pointed out some of the peculiarities in A-68A’s journey. For example, the berg’s rotation changed from counter-clockwise to clockwise and then back again. Occasionally the berg made quick progress, and at times it came to a halt. Sometimes it drifted straight, and other times it drifted in circles.

    History has shown that icebergs travel complex paths on their drift northward from the Southern Ocean into the warmer waters of the South Atlantic. David Long, a polar ice scientist at Brigham Young University, noted similarities between A-68A’s journey and iceberg A-43B. In 2004, that iceberg stalled for several months in a similar location as A-68A before ultimately drifting around the island.

    Strübing thinks that studying the drift of A-68A in detail could help scientists learn more about ocean dynamics in the region, while improving models of the paths of icebergs large and small. That’s important because massive icebergs—and the smaller pieces that break from them—are especially hazardous when they drift into the Southern Ocean’s main shipping routes.

    NASA Earth Observatory images by Lauren Dauphin, using VIIRS data from NASA EOSDIS/LANCE and GIBS/Worldview and the Suomi National Polar-orbiting Partnership, MODIS data from NASA EOSDIS/LANCE and GIBS/Worldview, ocean bathymetry data from the British Oceanographic Data Center’s General Bathymetric Chart of the Oceans (GEBCO), and digital elevation data from the British Antarctic Survey.

    While A-68A is following a similar path of many icebergs before it, the details of its journey are unique. In April 2020, A-68A was already adrift in relatively warm waters near the South Orkney Islands, about 800 kilometers (500 miles) from where it broke from the Antarctic ice shelf in 2017. Over the course of the austral winter, sea ice grew to mostly surround A-68A, according to Christopher Readinger of the U.S. National Ice Center (USNIC). Then, currents and wind carried the iceberg out of the sea ice. For several months the berg meandered north, spinning and revolving around oceanic eddies, until it was recently kicked to the northeast toward South Georgia.

    News reports have pointed to a possible collision with the island, or that the iceberg could become stuck, or “grounded,” in the shallow waters surrounding it. Either outcome could mean trouble for the island’s abundant wildlife if the berg blocks the foraging routes of penguins and seals.

    “The currents and eddies are probably too chaotic to really make a prediction about where it will go and how fast it will get there besides some average component of north-east over the next few months,” Readinger said. “The recent news about it seems to be expecting that it will ground at South Georgia. I’m not so sure.”

    Long agrees, noting that historical precedent suggests the iceberg is likely to pass just south of South Georgia. “If it is close enough to the island, it could get caught in the vortex in ocean currents to the east of the island and be pulled back toward the island by counter currents, much as A-22A did more than a decade ago,” Long said. “If, however, it passes far enough to the south, it will miss the counter current the vortex and probably keep heading east-northeast.”

    Whether it becomes stuck or sails smoothly on by, Iceberg A-68A will eventually move past South Georgia. That’s when Readinger thinks the iceberg is likely to break up into smaller bergs, a few of which should be sizable enough to be named by the USNIC. For example, A-68C is located about 420 kilometers (260 miles) northeast of South Georgia in the image at the top of this page. That new berg, identified in April 2020, is already breaking up into smaller pieces and will soon be too small for USNIC scientists to track.

    References & Resources

    BBC News (2020, December 5) World’s biggest iceberg captured by RAF cameras. Accessed December 14, 2020.
    BYU Center for Remote Sensing (2020, December) Tracking Iceberg A68. Accessed December 14, 2020.
    The European Space Agency (2020, December 11) Iceberg on collision course with South Georgia. Accessed December 14, 2020.
    The European Space Agency (2020, November 26) Iceberg A-68A: hit or miss? Accessed December 14, 2020.
    Reuters Graphics (2020, December 11) World’s biggest iceberg heads for disaster. Accessed December 14, 2020.
    Twitter (2020, December 14) Stef Lhermitte. Accessed December 14, 2020.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    The Earth Observatory’s is to share with the public the images, stories, and discoveries about climate and the environment that emerge from NASA research, including its satellite missions, in-the-field research, and climate models. The Earth Observatory staff is supported by the Climate and Radiation Laboratory, and the Hydrospheric and Biospheric Sciences Laboratory located at NASA Goddard Space Flight Center.

     
  • richardmitnick 2:43 pm on August 17, 2020 Permalink | Reply
    Tags: "NASA Researchers Track Slowly Splitting 'Dent' in Earth’s Magnetic Field", A small but evolving dent in Earth’s magnetic field can cause big headaches for satellites., , , , , , NASA Earth Observatory, South Atlantic Anomaly   

    From NASA Earth Observatory: “NASA Researchers Track Slowly Splitting ‘Dent’ in Earth’s Magnetic Field” 

    NASA Earth Observatory

    From NASA Earth Observatory

    Aug. 17, 2020

    Mara Johnson-Groh
    Jessica Merzdorf
    jessica.v.merzdorf@nasa.gov
    NASA’s Goddard Space Flight Center, Greenbelt, Md.

    1
    This stereoscopic visualization shows a simple model of the Earth’s magnetic field. The magnetic field partially shields the Earth from harmful charged particles emanating from the Sun. Credit: NASA’s Goddard Space Flight Center.

    A small but evolving dent in Earth’s magnetic field can cause big headaches for satellites.

    Earth’s magnetic field acts like a protective shield around the planet, repelling and trapping charged particles from the Sun. But over South America and the southern Atlantic Ocean, an unusually weak spot in the field – called the South Atlantic Anomaly, or SAA – allows these particles to dip closer to the surface than normal. Particle radiation in this region can knock out onboard computers and interfere with the data collection of satellites that pass through it – a key reason why NASA scientists want to track and study the anomaly.

    The South Atlantic Anomaly is also of interest to NASA’s Earth scientists who monitor the changes in magnetic field strength there, both for how such changes affect Earth’s atmosphere and as an indicator of what’s happening to Earth’s magnetic fields, deep inside the globe.

    Currently, the SAA creates no visible impacts on daily life on the surface. However, recent observations and forecasts show that the region is expanding westward and continuing to weaken in intensity. It is also splitting – recent data shows the anomaly’s valley, or region of minimum field strength, has split into two lobes, creating additional challenges for satellite missions.

    A host of NASA scientists in geomagnetic, geophysics, and heliophysics research groups observe and model the SAA, to monitor and predict future changes – and help prepare for future challenges to satellites and humans in space.


    Earth’s magnetic field acts like a protective shield around the planet, repelling and trapping charged particles from the Sun. But over South America and the southern Atlantic Ocean, an unusually weak spot in the field – called the South Atlantic Anomaly, or SAA – allows these particles to dip closer to the surface than normal. Currently, the SAA creates no visible impacts on daily life on the surface. However, recent observations and forecasts show that the region is expanding westward and continuing to weaken in intensity. The South Atlantic Anomaly is also of interest to NASA’s Earth scientists who monitor the changes in magnetic strength there, both for how such changes affect Earth’s atmosphere and as an indicator of what’s happening to Earth’s magnetic fields, deep inside the globe. Credits: NASA’s Goddard Space Flight Center.

    It’s what’s inside that counts

    The South Atlantic Anomaly arises from two features of Earth’s core: The tilt of its magnetic axis, and the flow of molten metals within its outer core.

    Earth is a bit like a bar magnet, with north and south poles that represent opposing magnetic polarities and invisible magnetic field lines encircling the planet between them. But unlike a bar magnet, the core magnetic field is not perfectly aligned through the globe, nor is it perfectly stable. That’s because the field originates from Earth’s outer core: molten, iron-rich and in vigorous motion 1800 miles below the surface. These churning metals act like a massive generator, called the geodynamo, creating electric currents that produce the magnetic field.

    As the core motion changes over time, due to complex geodynamic conditions within the core and at the boundary with the solid mantle up above, the magnetic field fluctuates in space and time too. These dynamical processes in the core ripple outward to the magnetic field surrounding the planet, generating the SAA and other features in the near-Earth environment – including the tilt and drift of the magnetic poles, which are moving over time. These evolutions in the field, which happen on a similar time scale to the convection of metals in the outer core, provide scientists with new clues to help them unravel the core dynamics that drive the geodynamo.

    “The magnetic field is actually a superposition of fields from many current sources,” said Terry Sabaka, a geophysicist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. Regions outside of the solid Earth also contribute to the observed magnetic field. However, he said, the bulk of the field comes from the core.

    The forces in the core and the tilt of the magnetic axis together produce the anomaly, the area of weaker magnetism – allowing charged particles trapped in Earth’s magnetic field to dip closer to the surface.

    The Sun expels a constant outflow of particles and magnetic fields known as the solar wind and vast clouds of hot plasma and radiation called coronal mass ejections. When this solar material streams across space and strikes Earth’s magnetosphere, the space occupied by Earth’s magnetic field, it can become trapped and held in two donut-shaped belts around the planet called the Van Allen Belts.

    Magnetosphere of Earth, original bitmap from NASA. SVG rendering by Aaron Kaase

    The belts restrain the particles to travel along Earth’s magnetic field lines, continually bouncing back and forth from pole to pole. The innermost belt begins about 400 miles from the surface of Earth, which keeps its particle radiation a healthy distance from Earth and its orbiting satellites.

    However, when a particularly strong storm of particles from the Sun reaches Earth, the Van Allen belts can become highly energized and the magnetic field can be deformed, allowing the charged particles to penetrate the atmosphere.

    “The observed SAA can be also interpreted as a consequence of weakening dominance of the dipole field in the region,” said Weijia Kuang, a geophysicist and mathematician in Goddard’s Geodesy and Geophysics Laboratory. “More specifically, a localized field with reversed polarity grows strongly in the SAA region, thus making the field intensity very weak, weaker than that of the surrounding regions.”

    A pothole in space

    Although the South Atlantic Anomaly arises from processes inside Earth, it has effects that reach far beyond Earth’s surface. The region can be hazardous for low-Earth orbit satellites that travel through it. If a satellite is hit by a high-energy proton, it can short-circuit and cause an event called single event upset or SEU. This can cause the satellite’s function to glitch temporarily or can cause permanent damage if a key component is hit. In order to avoid losing instruments or an entire satellite, operators commonly shut down non-essential components as they pass through the SAA. Indeed, NASA’s Ionospheric Connection Explorer regularly travels through the region and so the mission keeps constant tabs on the SAA’s position.

    The International Space Station, which is in low-Earth orbit, also passes through the SAA. It is well protected, and astronauts are safe from harm while inside. However, the ISS has other passengers affected by the higher radiation levels: Instruments like the Global Ecosystem Dynamics Investigation mission, or GEDI, collect data from various positions on the outside of the ISS. The SAA causes “blips” on GEDI’s detectors and resets the instrument’s power boards about once a month, said Bryan Blair, the mission’s deputy principal investigator and instrument scientist, and a lidar instrument scientist at Goddard.

    “These events cause no harm to GEDI,” Blair said. “The detector blips are rare compared to the number of laser shots – about one blip in a million shots – and the reset line event causes a couple of hours of lost data, but it only happens every month or so.”

    In addition to measuring the SAA’s magnetic field strength, NASA scientists have also studied the particle radiation in the region with the Solar, Anomalous, and Magnetospheric Particle Explorer, or SAMPEX – the first of NASA’s Small Explorer missions, launched in 1992 and providing observations until 2012. One study, led by NASA heliophysicist Ashley Greeley as part of her doctoral thesis, used two decades of data from SAMPEX to show that the SAA is slowly but steadily drifting in a northwesterly direction. The results helped confirm models created from geomagnetic measurements and showed how the SAA’s location changes as the geomagnetic field evolves.

    “These particles are intimately associated with the magnetic field, which guides their motions,” said Shri Kanekal, a researcher in the Heliospheric Physics Laboratory at NASA Goddard. “Therefore, any knowledge of particles gives you information on the geomagnetic field as well.”

    Greeley’s results, published in the journal Space Weather, were also able to provide a clear picture of the type and amount of particle radiation satellites receive when passing through the SAA, which emphasized the need for continuing monitoring in the region.

    The information Greeley and her collaborators garnered from SAMPEX’s in-situ measurements has also been useful for satellite design. Engineers for the Low-Earth Orbit, or LEO, satellite used the results to design systems that would prevent a latch-up event from causing failure or loss of the spacecraft.

    Modeling a safer future for satellites

    In order to understand how the SAA is changing and to prepare for future threats to satellites and instruments, Sabaka, Kuang and their colleagues use observations and physics to contribute to global models of Earth’s magnetic field.

    The team assesses the current state of the magnetic field using data from the European Space Agency’s Swarm constellation, previous missions from agencies around the world, and ground measurements. Sabaka’s team teases apart the observational data to separate out its source before passing it on to Kuang’s team. They combine the sorted data from Sabaka’s team with their core dynamics model to forecast geomagnetic secular variation (rapid changes in the magnetic field) into the future.

    The geodynamo models are unique in their ability to use core physics to create near-future forecasts, said Andrew Tangborn, a mathematician in Goddard’s Planetary Geodynamics Laboratory.

    “This is similar to how weather forecasts are produced, but we are working with much longer time scales,” he said. “This is the fundamental difference between what we do at Goddard and most other research groups modeling changes in Earth’s magnetic field.”

    One such application that Sabaka and Kuang have contributed to is the International Geomagnetic Reference Field, or IGRF. Used for a variety of research from the core to the boundaries of the atmosphere, the IGRF is a collection of candidate models made by worldwide research teams that describe Earth’s magnetic field and track how it changes in time.

    “Even though the SAA is slow-moving, it is going through some change in morphology, so it’s also important that we keep observing it by having continued missions,” Sabaka said. “Because that’s what helps us make models and predictions.”

    The changing SAA provides researchers new opportunities to understand Earth’s core, and how its dynamics influence other aspects of the Earth system, said Kuang. By tracking this slowly evolving “dent” in the magnetic field, researchers can better understand the way our planet is changing and help prepare for a safer future for satellites.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    The Earth Observatory’s is to share with the public the images, stories, and discoveries about climate and the environment that emerge from NASA research, including its satellite missions, in-the-field research, and climate models. The Earth Observatory staff is supported by the Climate and Radiation Laboratory, and the Hydrospheric and Biospheric Sciences Laboratory located at NASA Goddard Space Flight Center.

     
  • richardmitnick 8:11 am on May 12, 2020 Permalink | Reply
    Tags: "Antarctic Iceberg Breaks and Makes a New Berg", , , Iceberg A-68A, NASA Earth Observatory   

    From NASA Earth Observatory: “Antarctic Iceberg Breaks and Makes a New Berg” 

    NASA Earth Observatory

    From NASA Earth Observatory

    May 4th, 2020
    Kathryn Hansen

    Antarctic iceberg A-68A, which broke from the Larsen C Ice Shelf in 2017, has been floating solo in recent years. Not anymore. The colossal iceberg finally fractured in late April 2020, spawning a new companion named A-68C.

    1
    The break was not exactly surprising. A few weeks ago, we published this image (above) showing Iceberg A-68A on April 9, 2020. The iceberg on that day was still intact, but it had drifted north into dangerously warm waters. Christopher Readinger of the U.S. National Ice Center (USNIC) noted at the time:

    “I’m surprised at how well it’s sticking together. It’s been in warmer water for a few months now and it’s not exactly a very thick berg, so I expect it will break up sometime soon, but it’s showing no signs of that yet.”

    Less than two weeks later, that’s exactly what happened. Satellite images on April 22 showed that a new iceberg had broken off from A-68A. The pair is now drifting at the edge of the Weddell Sea and South Atlantic Ocean, near the South Orkney Islands. The image below, acquired by the Visible Infrared Imaging Radiometer Suite (VIIRS) on the NASA-NOAA Suomi-NPP satellite, shows the bergs on May 3, 2020.

    NOAA Suomi-NPP satellite via NASA Goddard

    2
    Iceberg A-68C measures about 11 nautical miles long and 7 nautical miles wide (20 by 13 kilometers). That’s small compared to its parent berg A-68A, which now measures 82 by 26 nautical miles (152 by 48 kilometers), but it is large enough to be named and tracked by the U.S. National Ice Center.

    Even after shedding the sizable piece of ice, A-68A is still the largest iceberg currently floating anywhere on Earth. It has calved only one other named berg, forming A-68B in July 2017 just after the initial calving event from the ice shelf.

    To see where the iceberg duo goes from here, you can follow them in satellite imagery available on Worldview.

    This entry was posted on Monday, May 4th, 2020 at 12:16 pm and is filed under Ice. You can follow any responses to this entry through the RSS 2.0 feed. You can skip to the end and leave a response. Pinging is currently not allowed.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    The Earth Observatory’s mission is to share with the public the images, stories, and discoveries about climate and the environment that emerge from NASA research, including its satellite missions, in-the-field research, and climate models. The Earth Observatory staff is supported by the Climate and Radiation Laboratory, and the Hydrospheric and Biospheric Sciences Laboratory located at NASA Goddard Space Flight Center.

     
  • richardmitnick 8:58 am on April 23, 2018 Permalink | Reply
    Tags: , , , Everything You Ever Wanted to Know About Earth’s Past Climates, , NASA Earth Observatory,   

    From Smithsonian.com: “Everything You Ever Wanted to Know About Earth’s Past Climates” 

    smithsonian
    Smithsonian.com

    April 16, 2018
    Rachel E. Gross

    They have a lot to tell us about our future.


    1:23:37

    In Silent Spring, Rachel Carson considers the Western sagebrush. “For here the natural landscape is eloquent of the interplay of forces that have created it,” she writes. “It is spread before us like the pages of an open book in which we can read why the land is what it is, and why we should preserve its integrity. But the pages lie unread.” She is lamenting the disappearance of a threatened landscape, but she may just as well be talking about markers of paleoclimate.

    To know where you’re going, you have to know where you’ve been. That’s particularly true for climate scientists, who need to understand the full range of the planet’s shifts in order to chart the course of our future. But without a time machine, how do they get this kind of data?

    Like Carson, they have to read the pages of the Earth. Fortunately, the Earth has kept diaries. Anything that puts down yearly layers—ocean corals, cave stalagmites, long-lived trees, tiny shelled sea creatures—faithfully records the conditions of the past. To go further, scientists dredge sediment cores and ice cores from the bottom of the ocean and the icy poles, which write their own memoirs in bursts of ash and dust and bubbles of long-trapped gas.

    In a sense, then, we do have time machines: Each of these proxies tells a slightly different story, which scientists can weave together to form a more complete understanding of Earth’s past.

    In March, the Smithsonian Institution’s National Museum of Natural History held a three-day Earth’s Temperature History Symposium that brought teachers, journalists, researchers and the public together to enhance their understanding of paleoclimate. During an evening lecture, Gavin Schmidt, climate modeler and director of NASA’s Goddard Institute for Space Studies, and Richard Alley, a world-famous geologist at Pennsylvania State University, explained how scientists use Earth’s past climates to improve the climate models we use to predict our future.

    Here is your guide to Earth’s climate pasts—not just what we know, but how we know it.

    How do we look into Earth’s past climate?

    It takes a little creativity to reconstruct Earth’s past incarnations. Fortunately, scientists know the main natural factors that shape climate. They include volcanic eruptions whose ash blocks the sun, changes in Earth’s orbit that shift sunlight to different latitudes, circulation of oceans and sea ice, the layout of the continents, the size of the ozone hole, blasts of cosmic rays, and deforestation. Of these, the most important are greenhouse gases that trap the sun’s heat, particularly carbon dioxide and methane.

    As Carson noted, Earth records these changes in its landscapes: in geologic layers, fossil trees, fossil shells, even crystallized rat pee—basically anything really old that gets preserved. Scientists can open up these diary pages and ask them what was going on at that time. Tree rings are particularly diligent record-keepers, recording rainfall in their annual rings; ice cores can keep exquisitely detailed accounts of seasonal conditions going back nearly a million years.

    1
    Ice cores reveal annual layers of snowfall, volcanic ash and even remnants of long-dead civilizations. (NASA’s Goddard / Ludovic Brucker)

    What else can an ice core tell us?

    “Wow, there’s so much,” says Alley, who spent five field seasons coring ice from the Greenland ice sheet. Consider what an ice core actually is: a cross-section of layers of snowfall going back millennia.

    When snow blankets the ground, it contains small air spaces filled with atmospheric gases. At the poles, older layers become buried and compressed into ice, turning these spaces into bubbles of past air, as researchers Caitlin Keating-Bitonti and Lucy Chang write in Smithsonian.com. Scientists use the chemical composition of the ice itself (the ratio of the heavy and light isotopes of oxygen in H2O) to estimate temperature. In Greenland and Antarctica, scientists like Alley extract inconceivably long ice cores—some more than two miles long!

    Ice cores tell us how much snow fell during a particular year. But they also reveal dust, sea salt, ash from faraway volcanic explosions, even the pollution left by Roman plumbing. “If it’s in the air it’s in the ice,” says Alley. In the best cases, we can date ice cores to their exact season and year, counting up their annual layers like tree rings. And ice cores preserve these exquisite details going back hundreds of thousands of years, making them what Alley calls “the gold standard” of paleoclimate proxies.

    Wait, but isn’t Earth’s history much longer than that?

    Yes, that’s right. Paleoclimate scientists need to go back millions of years—and for that we need things even older than ice cores. Fortunately, life has a long record. The fossil record of complex life reaches back to somewhere around 600 million years. That means we have definite proxies for changes in climate going back approximately that far. One of the most important is the teeth of conodonts—extinct, eel-like creatures—which go back 520 million years.

    But some of the most common climate proxies at this timescale are even more miniscule. Foraminifera (known as “forams”) and diatoms are unicellular beings that tend to live on the ocean seafloor, and are often no bigger than the period at the end of this sentence. Because they are scattered all across the Earth and have been around since the Jurassic, they’ve left a robust fossil record for scientists to probe past temperatures. Using oxygen isotopes in their shells, we can reconstruct ocean temperatures going back more than 100 million years ago.

    “In every outthrust headland, in every curving beach, in every grain of sand there is a story of the earth,” Carson once wrote. Those stories, it turns out, are also hiding in the waters that created those beaches, and in creatures smaller than a grain of sand.

    2
    Foraminifera. (Ernst Haeckel)

    How much certainty do we have for deep past?

    For paleoclimate scientists, life is crucial: if you have indicators of life on Earth, you can interpret temperature based on the distribution of organisms.

    But when we’ve gone back so far that there are no longer even any conodont teeth, we’ve lost our main indicator. Past that we have to rely on the distribution of sediments, and markers of past glaciers, which we can extrapolate out to roughly indicate climate patterns. So the further back we go, the fewer proxies we have, and the less granular our understanding becomes. “It just gets foggier and foggier,” says Brian Huber, a Smithsonian paleobiologist who helped organize the symposium along with fellow paleobiologist research scientist and curator Scott Wing.

    How does paleoclimate show us the importance of greenhouse gases?

    Greenhouse gases, as their name suggests, work by trapping heat. Essentially, they end up forming an insulating blanket for the Earth. (You can get more into the basic chemistry here.) If you look at a graph of past Ice Ages, you can see that CO2 levels and Ice Ages (or global temperature) align. More CO2 equals warmer temperatures and less ice, and vice versa. “And we do know the direction of causation here,” Alley notes. “It is primarily from CO2 to (less) ice. Not the other way around.”

    We can also look back at specific snapshots in time to see how Earth responds to past CO2 spikes. For instance, in a period of extreme warming during Earth’s Cenozoic era about 55.9 million years ago, enough carbon was released to about double the amount of CO2 in the atmosphere. The consequentially hot conditions wreaked havoc, causing massive migrations and extinctions; pretty much everything that lived either moved or went extinct. Plants wilted. Oceans acidified and heated up to the temperature of bathtubs.

    Unfortunately, this might be a harbinger for where we’re going. “This is what’s scary to climate modelers,” says Huber. “At the rate we’re going, we’re kind of winding back time to these periods of extreme warmth.” That’s why understanding carbon dioxide’s role in past climate change helps us forecast future climate change.

    That sounds pretty bad.

    Yep.

    I’m really impressed by how much paleoclimate data we have. But how does a climate model work?

    Great question! In science, you can’t make a model unless you understand the basic principles underlying the system. So the mere fact that we’re able to make good models means that we understand how this all works. A model is essentially a simplified version of reality, based on what we know about the laws of physics and chemistry. Engineers use mathematical models to build structures that millions of people rely on, from airplanes to bridges.

    Our models are based on a framework of data, much of which comes from the paleoclimate proxies scientists have collected from every corner of the world. That’s why it’s so important for data and models to be in conversation with each other. Scientists test their predictions on data from the distant past, and try to fix any discrepancies that arise. “We can go back in time and evaluate and validate the results of these models to make better predictions for what’s going to happen in the future,” says Schmidt.

    Here’s a model:

    3

    It’s pretty. I hear the models aren’t very accurate, though.

    By their very nature, models are always wrong. Think of them as an approximation, our best guess.

    But ask yourself: do these guesses give us more information than we had previously? Do they provide useful predictions we wouldn’t otherwise have? Do they allow us to ask new, better questions? “As we put all of these bits together we end up with something that looks very much like the planet,” says Schmidt. “We know it’s incomplete. We know there are things that we haven’t included, we know that we’ve put in things that are a little bit wrong. But the basic patterns we see in these models are recognizable … as the patterns that we see in satellites all the time.”

    So we should trust them to predict the future?

    The models faithfully reproduce the patters we see in Earth’s past, present—and in some cases, future. We are now at the point where we can compare early climate models—those of the late 1980s and 1990s that Schmidt’s team at NASA worked on—to reality. “When I was a student, the early models told us how it would warm,” says Alley. “That is happening. The models are successfully predictive as well as explanatory: they work.” Depending on where you stand, that might make you say “Oh goody! We were right!” or “Oh no! We were right.”

    To check models’ accuracy, researchers go right back to the paleoclimate data that Alley and others have collected. They run models into the distant past, and compare them to the data that they actually have.

    “If we can reproduce ancient past climates where we know what happened, that tells us that those models are a really good tool for us to know what’s going to happen in the future,” says Linda Ivany, a paleoclimate scientist at Syracuse University. Ivany’s research proxies are ancient clams, whose shells record not only yearly conditions but individual winters and summers going back 300 million years—making them a valuable way to check models. “The better the models get at recovering the past,” she says, “the better they’re going to be at predicting the future.”

    Paleoclimate shows us that Earth’s climate has changed dramatically. Doesn’t that mean that, in a relative sense, today’s changes aren’t a big deal?

    When Richard Alley tries to explain the gravity of manmade climate change, he often invokes a particular annual phenomenon: the wildfires that blaze in the hills of Los Angeles every year. These fires are predictable, cyclical, natural. But it’d be crazy to say that, since fires are the norm, it’s fine to let arsonists set fires too. Similarly, the fact that climate has changed over millions of years doesn’t mean that manmade greenhouse gases aren’t a serious global threat.

    “Our civilization is predicated on stable climate and sea level,” says Wing, “and everything we know from the past says that when you put a lot of carbon in the atmosphere, climate and sea level change radically.”

    Since the Industrial Revolution, human activities have helped warm the globe 2 degrees F, one-quarter of what Schmidt deems an “Ice Age Unit”—the temperature change that the Earth goes through between an Ice Age and a non-Ice Age. Today’s models predict another 2 to 6 degrees Celsius of warming by 2100—at least 20 times faster than past bouts of warming over the past 2 million years.

    ______________________________________________________________
    From NASA Earth Observatory

    How is Today’s Warming Different from the Past?

    Earth has experienced climate change in the past without help from humanity. We know about past climates because of evidence left in tree rings, layers of ice in glaciers, ocean sediments, coral reefs, and layers of sedimentary rocks. For example, bubbles of air in glacial ice trap tiny samples of Earth’s atmosphere, giving scientists a history of greenhouse gases that stretches back more than 800,000 years. The chemical make-up of the ice provides clues to the average global temperature.

    See the Earth Observatory’s series Paleoclimatology for details about how scientists study past climates.

    3
    Glacial ice and air bubbles trapped in it (top) preserve an 800,000-year record of temperature & carbon dioxide. Earth has cycled between ice ages (low points, large negative anomalies) and warm interglacials (peaks). (Photograph courtesy National Snow & Ice Data Center. NASA graph by Robert Simmon, based on data from Jouzel et al., 2007.)

    Using this ancient evidence, scientists have built a record of Earth’s past climates, or “paleoclimates.” The paleoclimate record combined with global models shows past ice ages as well as periods even warmer than today. But the paleoclimate record also reveals that the current climatic warming is occurring much more rapidly than past warming events.

    As the Earth moved out of ice ages over the past million years, the global temperature rose a total of 4 to 7 degrees Celsius over about 5,000 years. In the past century alone, the temperature has climbed 0.7 degrees Celsius, roughly ten times faster than the average rate of ice-age-recovery warming.

    4
    Temperature histories from paleoclimate data (green line) compared to the history based on modern instruments (blue line) suggest that global temperature is warmer now than it has been in the past 1,000 years, and possibly longer. (Graph adapted from Mann et al., 2008.)

    Models predict that Earth will warm between 2 and 6 degrees Celsius in the next century. When global warming has happened at various times in the past two million years, it has taken the planet about 5,000 years to warm 5 degrees. The predicted rate of warming for the next century is at least 20 times faster. This rate of change is extremely unusual.

    See the full NASA Earth Observatory article here .
    ______________________________________________________________

    Of course there are uncertainties: “We could have a debate about whether we’re being a little too optimistic or not,” says Alley. “But not much debate about whether we’re being too scary or not.” Considering how right we were before, we should ignore history at our own peril.

    ______________________________________________________________

    See the full article here .

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  • richardmitnick 6:20 pm on January 2, 2016 Permalink | Reply
    Tags: , , NASA Earth Observatory,   

    From NASA Earth: “Freeze and Thaw in the North” 

    NASA Earth Observatory

    NASA Earth Observatory

    1.2.16
    No writer credit found.

    Temp 1
    acquired March 5, 2015

    At the planet’s highest northern latitudes, nearly all of the fresh water is frozen. Even the water in the soil is locked away as ice, making it mostly inaccessible to plants. But just a short distance to the south, in the boreal areas of Alaska, Canada, Siberia, and Scandinavia, the landscape comes alive each year after the spring thaw.

    The transition is relatively rapid, occurring over just a few weeks, and coincides with increasing sunlight and spring snowmelt. Rapid warming releases liquid water. As liquid water becomes more readily available, plant and animal activity is energized. The land greens up, and animals return to graze.

    “I’m always impressed by how rapidly northern landscapes transition from frozen and dormant conditions in the winter to a rapid burst of life and activity in the spring,” said John Kimball, a scientist at the University of Montana.

    The transition between frozen and thawed land is something researchers have observed for more than 30 years with satellites. Now, NASA’s Soil Moisture Active Passive (SMAP) satellite is continuing that record.

    NASA SMAP
    NASA/SMAP

    Data from SMAP’s radar instrument were used to produce this map, which shows the freeze-thaw status of areas north of 45 degrees latitude on March 5, 2015, as spring approached. Frozen land is blue; thawed land is pink. The measurement is possible because frozen water forms crystalline structures that can be detected by satellites.

    Kimball and colleagues have mined 30 years of freeze-thaw patterns from the satellite record. In a paper published in 2012, the researchers showed that soils in the Northern Hemisphere thawed for as many as 7.5 days more in 2008 than they did in 1979. The change was primarily driven by an earlier start to the spring thaw and coincided with measureable warming in the region.

    “This was a real eye-opener to me,” Kimball said. “We found that the earlier spring-thaw was driving widespread increases in northern growing seasons.” The start and the length of the growing season have implications for how much carbon is exchanged between the land and atmosphere.

    Questions still remain. For example: How will larger areas of thaw affect carbon sources and sinks? How stable are areas of permafrost with continued global warming? But scientists are making progress. Freeze-thaw monitoring, according to Kimball, made a major advance thanks to the development of well-calibrated, long-term satellite soil moisture records. As those observations continue, and as they encompass more of the planet, it stands to reason that our understanding of the entire water cycle will improve.

    Read more in our feature story: A Little Bit of Water, A Lot of Impact.

    References and Related Reading
    Kim, Y. et al., (2012) Satellite detection of increasing Northern Hemisphere non-frozen seasons from 1979 to 2008: Implications for regional vegetation growth. Remote Sensing of Environment, 121 (2012), 472-487.
    NASA’s Jet Propulsion Laboratory (2015, March 13) Let it Go! SMAP Almost Ready to Map Frozen Soil. Accessed September 16, 2015.
    National Snow & Ice Data Center, Satellite Observations of Arctic Change. Accessed September 16, 2015.
    Natural Resources Canada (2015, September 20) Forest carbon. Accessed September 16, 2015.
    SMAP Mission Brochure (2014) Mapping Soil Moisture and Freeze/Thaw State from Space. Accessed September 16, 2015.

    NASA Earth Observatory map by Joshua Stevens, using data courtesy of JPL and the SMAP science team. Caption by Kathryn Hansen.

    See the full article here .

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  • richardmitnick 3:10 pm on December 29, 2015 Permalink | Reply
    Tags: , , , NASA Earth Observatory,   

    From NASA Earth: “Seafloor Features Are Revealed by the Gravity Field” 

    NASA Earth Observatory

    NASA Earth Observatory

    12.29.15
    No writer credit found.

    1
    acquired 2014 (NASA Earth Observatory maps by Joshua Stevens, using data from Sandwell, D. et al. [2014]. Caption by Mike Carlowicz.)

    It has been said that we have more complete maps of the surface of Mars or the Moon than we do of Earth. Close to 70 percent of our planet is covered by water, and that water refracts, absorbs, and reflects light so well that it can only penetrate a few tens to hundreds of meters. To humans and most satellite eyes, the deep ocean is opaque.

    But there are ways to visualize what the planet looks like beneath that watery shroud. Sonar-based (sounding) instruments mounted on ships can distinguish the shape (bathymetry) of the seafloor. But such maps can only be made for places where ships and sonar pass frequently. The majority of such measurements have been made along the major shipping routes of the world, interspersed with results from scientific expeditions over the past two centuries. About 5 to 15 percent of the global ocean floor has been mapped in this way, depending on how you define “mapped.”

    There is another way to see the depths of the ocean: by measuring the shape and gravity field of Earth, a discipline known as geodesy. David Sandwell of the Scripps Institution of Oceanography and Walter Smith of the National Oceanic and Atmospheric Administration have spent much of the past 25 years negotiating with military agencies and satellite operators to allow them acquire or gain access to measurements of the Earth’s gravity field and sea surface heights. The result of their collaborative efforts is a global data set that tells where the ridges and valleys are by showing where the planet’s gravity field varies.

    The map above shows a global view of gravity anomalies, as measured and assembled by Sandwell, Smith, and colleagues. Shades of orange and red represent areas where seafloor gravity is stronger (in milligals) than the global average, a phenomenon that mostly coincides with the location of underwater ridges, seamounts, and the edges of Earth’s tectonic plates. Shades of blue represent areas of lower gravity, corresponding largely with the deepest troughs in the ocean. The second map shows a tighter view of that data along the Mid-Atlantic Ridge between Africa and South America.

    Temp 1
    acquired 2014

    The maps were created through computer analysis and modeling of new satellite altimetry data from the European Space Agency’s CryoSat-2 and from the NASA-CNES Jason-1 (see at the end of this post), as well as older data from missions flown in the 1980s and 90s. CryoSat-2 was designed to collect data over Earth’s polar regions, but it also collected measurements over the oceans. Jason-1 was specifically designed to measure the height of the oceans, but it had to be adjusted to a slightly different orbit in order to acquire the data needed to see gravity anomalies.

    ESA CryoSat 2
    ESA/Cryosat 2

    But how does the height of the sea surface (which is what the altimeters measured) tell us something about gravity and the seafloor? Mountains and other seafloor features have a lot of mass, so they exert a gravitational pull on the water above and around them; essentially, seamounts pull more water toward their center of mass. This causes water to pile up in small but measurable bumps on the sea surface. (If you are wondering why a greater mass would not pull the water down, it is because water is incompressible; that is, it will not shrink into a smaller volume.)

    The new measurements of these tiny bumps on the sea surface were compared and combined with previous gravity measurements to make a map that is two- to four times more detailed than before. Through their work, Sandwell, Smith, and the team have charted thousands of previously uncharted mountains and abyssal hills. The new map gives an accurate picture of seafloor topography at a scale of 5 kilometers per pixel.

    Temp 2
    acquired 2014

    From these seafloor maps, scientists can further refine their understand of the evolution and motion of Earth’s tectonic plates and the continents they carry.

    4
    The key principle of plate tectonics is that the lithosphere exists as separate and distinct tectonic plates, which float on the fluid-like (visco-elastic solid) asthenosphere. The relative fluidity of the asthenosphere allows the tectonic plates to undergo motion in different directions. This map shows 15 of the largest plates. Note that the Indo-Australian Plate may be breaking apart into the Indian and Australian plates, which are shown separately on this map.

    They can also improve estimates of the depth of the seafloor in various regions and target new sonar surveys to further refine the details, especially in areas where there is thick sediment. This third map shows the gravity data as a cartographer would represent the seafloor, with darker blues representing deeper areas.

    References and Related Reading
    Sandwell, D. et al. (2014) New global marine gravity model from CryoSat-2 and Jason-1 reveals buried tectonic structure. Science, 346 (6205), 65–67.
    Scripps Institution of Oceanography (2014, October 2) Marine Gravity from Satellite Altimetry. Accessed December 23, 2015.
    Scripps Institution of Oceanography (2014, October 2) New Map Exposes Previously Unseen Details of Seafloor. Accessed December 23, 2015.
    Carlowicz, M. (1995, October 31) New Map of Seafloor Mirrors Surface. EOS, Transactions, AGU, 441–442.
    University of Sydney (2014, October 5) Mapping the Seafloor from Space. Accessed December 23, 2015.
    Scientific American (2014, October 9) Just How Little Do We Know about the Ocean Floor? Accessed December 23, 2015.
    Schmidt Ocean Institute (2013, March 12) The Ocean: Haven’t We Already Mapped It? Accessed December 23, 2015.
    NOAA National Ocean Service (2015) What is geodesy? Accessed December 23, 2015.
    NOAA National Ocean Service (2015) How much of the ocean have we explored? Accessed December 23, 2015.

    NASA Earth Observatory maps by Joshua Stevens, using data from Sandwell, D. et al. (2014). Caption by Mike Carlowicz.

    Instrument(s):
    Model
    JASON-1

    NASA Jason-1
    NASA/JPL JASON-1

    See the full article here .

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  • richardmitnick 5:07 pm on November 29, 2015 Permalink | Reply
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    From NASA Earth: A New Island 

    NASA Earth Observatory

    NASA Earth Observatory

    11.25.15

    1
    acquired November 6, 2013

    2
    acquired October 11, 2015

    Two years ago, a new island, or “nijima,” rose above the water line in the western Pacific, about 1,000 kilometers (600 miles) south of Tokyo. It grew out of the sea just 500 meters from Nishinoshima, another volcanic island. Over the past two years, that new island swallowed up its neighbor, and the merged island is now twelve times the size of the old island.

    The Operational Land Imager (OLI) on Landsat 8 captured these images of the old and new Nishinoshima.

    NASA Landsat 8 OLI
    OLI

    NASA LandSat 8
    Landsat 8

    The top image shows the area on November 6, 2013, two weeks before the eruption started. The second image was acquired on October 11, 2015, the most recent cloud-free view. In both images, pale areas just offshore likely reveal volcanic gases bubbling up from submerged vents or sediments disturbed by the eruption. Turn on the image comparison tool to see the transformation.

    Nishinoshima is part of the Ogasawara Islands, in the Volcano Islands arc.

    3
    The Ogasawara Islands, consisting of the Mukojima, Chichijima, and Hahajima island groups, are located far south of the Japanese home islands.

    It is located at 27°14’ North latitude and 140°52’ East longitude, about 130 kilometers (80 miles) from the nearest inhabited island. According to the Japanese coast guard, which surveyed the island on November 17, the island now stretches 1.9 kilometers from east to west and 1.95 kilometers from north to south. It stands about 100 meters above the sea surface.

    Lava continues to ooze out slowly, though there are occasional explosions of rock and ash as well. Investigators noted that the total surface area of the island decreased a bit from September to November 2015—2.67 square kilometers to 2.64—likely because of erosion of the coasts by wave action.

    You can see the evolution of the volcanic island by visiting out natural hazards event page.

    See the full article here .

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  • richardmitnick 1:05 pm on October 13, 2015 Permalink | Reply
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    From NASA Earth: “El Niño Strengthening” 

    NASA Earth Observatory

    NASA Earth Observatory

    1
    acquired October 5, 1997 – October 4, 2015

    The latest analyses from the National Oceanic and Atmospheric Administration and from NASA confirm that El Niño is strengthening and it looks a lot like the strong event that occurred in 1997–98. Observations of sea surface heights and temperatures, as well as wind patterns, show surface waters cooling off in the Western Pacific and warming significantly in the tropical Eastern Pacific.

    “Whether El Niño gets slightly stronger or a little weaker is not statistically significant now. This baby is too big to fail,” said Bill Patzert, a climatologist at NASA’s Jet Propulsion Laboratory. October sea level height anomalies show that 2015 is as big or bigger in heat content than 1997. “Over North America, this winter will definitely not be normal. However, the climatic events of the past decade make ‘normal’ difficult to define.”

    The maps above show a comparison of sea surface heights in the Pacific Ocean as observed at the beginning of October in 1997 and 2015. The measurements come from altimeters on the TOPEX/Poseidon mission (left) and Jason-2 (right); both show averaged sea surface height anomalies. Shades of red indicate where the ocean stood higher (in tens of millimeters) than the normal sea level because warmer water expands to fill more volume. Shades of blue show where sea level and temperatures were lower than average (contraction). Normal sea-level conditions appear in white.

    “The trade winds have been weakening again,” Patzert said. “This should strengthen this El Niño.” Weaker trade winds out of the eastern Pacific allow west wind bursts to push warm surface waters from the central and western Pacific toward the Americas. Click here [in the full article] to watch a video of Kelvin waves propagating across the ocean in the first seven months of 2015.

    In its October monthly update, scientists at NOAA’s Climate Prediction Center stated: “All multi-model averages predict a peak in late fall/early winter. The forecaster consensus unanimously favors a strong El Niño…Overall, there is an approximately 95 percent chance that El Niño will continue through Northern Hemisphere winter 2015–16.”

    2

    The July–September average of sea surface temperatures was 1.5°C above normal, NOAA reported, ranking third behind 1982 (1.6°C) and 1997 (1.7°C). The plot above shows sea surface temperatures in the tropical Pacific for all moderate to strong El Niño years since 1950.

    Both Patzert and NOAA forecasters believe the southern tier of North America, particularly southern California, is likely to see a cooler and wetter than normal winter, while the northern tier could be warmer and drier. But the sample of El Niños in the meteorological record are still too few and other elements of our changing climate are too new to say with certainty what the winter will bring.

    NASA Earth Observatory map by Jesse Allen, using Jason-2 and TOPEX/Posideon data provided by Akiko Kayashi and Bill Patzert, NASA/JPL Ocean Surface Topography Team. NASA Earth Observatory chart by Joshua Stevens, using data from NOAA. Caption by Mike Carlowicz.

    NASA Jason 2
    NASA/Jason-2

    NASA Topex Poseiden
    NASA TOPEX/Poseodon

    Instrument(s):
    TOPEX/Poseidon
    JASON-2

    See the original article for further reading references.

    See the full article here .

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  • richardmitnick 11:01 am on October 11, 2015 Permalink | Reply
    Tags: , , , NASA Earth Observatory, NASA Landsat 8   

    From NASA Earth: “Malaspina Glacier, Alaska” 

    NASA Earth Observatory

    NASA Earth Observatory

    1
    acquired September 24, 2014

    The ice of a piedmont glacier spills from a steep valley onto a relatively flat plain, where it spreads out unconstrained like pancake batter. Elephant Foot Glacier in northeastern Greenland is an excellent example; it is particularly noted for its symmetry. But the largest piedmont glacier in North America (and possibly the world) is Malaspina in southeastern Alaska.

    On September 24, 2014, the Operational Land Imager (OLI) on Landsat 8 acquired this image of Malaspina Glacier.

    NASA Landsat 8 OLI
    OLI

    NASA LandSat 8
    NASA LandSat 8

    The main source of ice comes from Seward Glacier, located at the top-center of this image. The Agassiz and Libbey glaciers are visible on the left side, and the Hayden and Marvine glaciers are on the right.

    The brown lines on the ice are moraines—areas where soil, rock, and other debris have been scraped up by the glacier and deposited at its sides. Where two glaciers flow together, the moraines merge to form a medial moraine. Glaciers that flow at a steady speed tend to have moraines that are relatively straight.

    But what causes the dizzying pattern of curves, zigzags, and loops of Malaspina’s moraines? Glaciers in this area of Alaska periodically “surge,”meaning they lurch forward quickly for one to several years. As a result of this irregular flow, the moraines at the edges and between glaciers can become folded, compressed, and sheared to form the characteristic loops seen on Malaspina. For instance, a surge in 1986 displaced moraines on the east side of Malaspina by as much as 5 kilometers (3 miles).

    See the full article for the list of references with links.

    See the full article here .

    Please help promote STEM in your local schools.

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