From The University of Delaware : “Fast-melting ice may contribute to ocean acidification”

U Delaware bloc

From The University of Delaware

9.29.22
Beth Miller
Photos courtesy of Zhangxian Ouyang, Wei-Jun Cai and Liza Wright-Fairbanks
Illustration by Jeffrey C. Chase

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A polar bear and two cubs visited the ice station where researchers — including Zhangxian Ouyang of the University of Delaware — were working during a recent visit to the Arctic ocean.

UD’s Wei-Jun Cai and collaborators find correlation between Arctic meltwater and changing ocean chemistry.

Wei-Jun Cai, an expert in marine chemistry at the University of Delaware, is sounding new alarm bells about the changing chemistry of the western region of the Arctic Ocean, where he and an international team of collaborators have found acidity levels increasing three to four times faster than ocean waters elsewhere.

They also identified a strong correlation between the accelerated rate of melting ice in the region and the rate of ocean acidification, a perilous combination that threatens the survival of plants, shellfish, coral reefs and other marine life and biological processes throughout the planet’s ecosystem.

The new study, published on Thursday, Sept. 30 in Science [below], the flagship journal of the American Association for the Advancement of Science, is the first analysis of Arctic acidification that includes data from more than two decades, spanning the period from 1994 to 2020.

Scientists have predicted that by 2050 — if not sooner — Arctic sea ice in this region will no longer survive the increasingly warm summer seasons. As a result of this sea-ice retreat each summer, the ocean’s chemistry will grow more acidic, with no persistent ice cover to slow or otherwise mitigate the advance.

That creates life-threatening problems for the enormously diverse population of sea creatures, plants and other living things that depend on a healthy ocean for survival. Crabs, for example, live in a crusty shell built from the calcium carbonate prevalent in ocean water. Polar bears rely on healthy fish populations for food, fish and sea birds rely on plankton and plants, and seafood is a key element of many humans’ diets.

That makes acidification of these distant waters a big deal for many of the planet’s inhabitants.

First, a quick refresher course on pH levels, which indicate how acidic or alkaline a given liquid is. Any liquid that contains water can be characterized by its pH level, which ranges from 0 to 14, with pure water considered neutral with a pH of 7. All levels lower than 7 are acidic, all levels greater than 7 are basic or alkaline, with each full step representing a tenfold difference in the hydrogen ion concentration. Examples on the acidic side include battery acid, which checks in at 0 pH, gastric acid (1), black coffee (5) and milk (6.5). Tilting toward basic are blood (7.4), baking soda (9.5), ammonia (11) and drain cleaner (14). Seawater is normally alkaline, with a pH value of around 8.1.

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Wei-Jun-Cai, the Mary A.S. Lighthipe Professor in UD’s School of Marine Science and Policy, has been studying the changing chemistry of the world’s oceans. A recent study of Arctic Ocean waters showed rapid acidification and Cai and his collaborators have published their findings in the journal Science.

Cai, the Mary A.S. Lighthipe Professor in the School of Marine Science and Policy in UD’s College of Earth, Ocean and Environment, has published significant research on the changing chemistry of the planet’s oceans and this month completed a cruise from Nova Scotia to Florida, serving as chief scientist among 27 aboard the research vessel. The work, supported by the National Oceanic and Atmospheric Administration (NOAA), includes four areas of study: The East Coast, the Gulf of Mexico, the Pacific Coast and the Alaska/Arctic region.

The new study in Science included UD postdoctoral researcher Zhangxian Ouyang, who participated in a recent voyage to collect data in the Chukchi Sea and Canada Basin in the Arctic Ocean.

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Researchers, including UD’s Zhangxian Ouyang, traveled aboard the icebreaker R/V Xue Long into an active melting zone in the Arctic Ocean to get samples for analysis.

The first author on the publication was Di Qi, who works with Chinese research institutes in Xiamen and Qingdao. Also collaborating on this publication were scientists from Seattle, Sweden, Russia and six other Chinese research sites.

“You can’t just go by yourself,” Cai said. “This international collaboration is very important for collecting long-term data over a large area in the remote ocean. In recent years, we have also collaborated with Japanese scientists as accessing the Arctic water was even harder in the past three years due to COVID-19. And we always have European scientists participating.”

Cai said he and Qi both were baffled when they first reviewed the Arctic data together during a conference in Shanghai. The acidity of the water was increasing three to four times faster than ocean waters elsewhere.

That was stunning indeed. But why was it happening?

Cai soon identified a prime suspect: the increased melt of sea ice during the Arctic’s summer season.

Historically, the Arctic’s sea ice has melted in shallow marginal regions during the summer seasons. That started to change in the 1980s, Cai said, but waxed and waned periodically. In the past 15 years, the ice melt has accelerated, advancing into the deep basin in the north.

For a while, scientists thought the melting ice could provide a promising “carbon sink,” where carbon dioxide from the atmosphere would be sucked into the cold, carbon-hungry waters that had been hidden under the ice. That cold water would hold more carbon dioxide than warmer waters could and might help to offset the effects of increased carbon dioxide elsewhere in the atmosphere.

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UD’s Zhangxian Ouyang collects samples on the ice.

When Cai first studied the Arctic Ocean in 2008, he saw that the ice had melted beyond the Chukchi Sea in the northwest corner of the region, all the way to the Canada Basin — far beyond its typical range. He and his collaborators found that the fresh meltwater did not mix into deeper waters, which would have diluted the carbon dioxide. Instead, the surface water soaked up the carbon dioxide until it reached about the same levels as in the atmosphere and then stopped collecting it. They reported this result in a paper in Science in 2010.

That would also change the pH level of the Arctic waters, they knew, reducing the alkaline levels of the seawater and reducing its ability to resist acidification. But how much? And how soon? It took them another decade to collect enough data to derive a sound conclusion on the long-term acidification trend.

Analyzing data gathered from 1994 to 2020 – the first time such a long-term perspective was possible — Cai, Qi and their collaborators found an extraordinary increase in acidification and a strong correlation with the increasing rate of melting ice.

They point to sea-ice melt as the key mechanism to explain this rapid pH decrease, because it changes the physics and chemistry of the surface water in three primary ways:

The water under the sea ice, which had a deficit of carbon dioxide, now is exposed to the atmospheric carbon dioxide and can take up carbon dioxide freely.

The seawater mixed with meltwater is light and cannot mix easily into deeper waters, which means the carbon dioxide taken from the atmosphere is concentrated at the surface.

The meltwater dilutes the carbonate ion concentration in the seawater, weakening its ability to neutralize the carbon dioxide into bicarbonate and rapidly decreasing ocean pH.

Cai said more research is required to further refine the above mechanism and better predict future changes, but the data so far show again the far-reaching ripple effects of climate change.

“If all of the multiple-year ice is replaced by first-year ice, then there will be lower alkalinity and lower buffer capacity and acidification continues,” he said. “By 2050, we think all of the ice will be gone in the summer. Some papers predict that will happen by 2030. And if we follow the current trend for 20 more years, the summer acidification will be really, really strong.”

No one knows exactly what that will do to the creatures and plants and other living things that depend on healthy ocean waters.

“How will this affect the biology there?” Cai asked. “That is why this is important.”

Science paper:
Science

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U Delaware campus

The University of Delaware is a public land-grant research university located in Newark, Delaware. University of Delaware (US) is the largest university in Delaware. It offers three associate’s programs, 148 bachelor’s programs, 121 master’s programs (with 13 joint degrees), and 55 doctoral programs across its eight colleges. The main campus is in Newark, with satellite campuses in Dover, the Wilmington area, Lewes, and Georgetown. It is considered a large institution with approximately 18,200 undergraduate and 4,200 graduate students. It is a privately governed university which receives public funding for being a land-grant, sea-grant, and space-grant state-supported research institution.

The University of Delaware is classified among “R1: Doctoral Universities – Very high research activity”. According to The National Science Foundation, UD spent $186 million on research and development in 2018, ranking it 119th in the nation. It is recognized with the Community Engagement Classification by the Carnegie Foundation for the Advancement of Teaching.

The University of Delaware is one of only four schools in North America with a major in art conservation. In 1923, it was the first American university to offer a study-abroad program.

The University of Delaware traces its origins to a “Free School,” founded in New London, Pennsylvania in 1743. The school moved to Newark, Delaware by 1765, becoming the Newark Academy. The academy trustees secured a charter for Newark College in 1833 and the academy became part of the college, which changed its name to Delaware College in 1843. While it is not considered one of the colonial colleges because it was not a chartered institution of higher education during the colonial era, its original class of ten students included George Read, Thomas McKean, and James Smith, all three of whom went on to sign the Declaration of Independence. Read also later signed the United States Constitution.

Science, Technology and Advanced Research (STAR) Campus

On October 23, 2009, The University of Delaware signed an agreement with Chrysler to purchase a shuttered vehicle assembly plant adjacent to the university for $24.25 million as part of Chrysler’s bankruptcy restructuring plan. The university has developed the 272-acre (1.10 km^2) site into the Science, Technology and Advanced Research (STAR) Campus. The site is the new home of University of Delaware (US)’s College of Health Sciences, which includes teaching and research laboratories and several public health clinics. The STAR Campus also includes research facilities for University of Delaware (US)’s vehicle-to-grid technology, as well as Delaware Technology Park, SevOne, CareNow, Independent Prosthetics and Orthotics, and the East Coast headquarters of Bloom Energy. In 2020 [needs an update], University of Delaware expects to open the Ammon Pinozzotto Biopharmaceutical Innovation Center, which will become the new home of the UD-led National Institute for Innovation in Manufacturing Biopharmaceuticals. Also, Chemours recently opened its global research and development facility, known as the Discovery Hub, on the STAR Campus in 2020. The new Newark Regional Transportation Center on the STAR Campus will serve passengers of Amtrak and regional rail.

Academics

The university is organized into nine colleges:

Alfred Lerner College of Business and Economics
College of Agriculture and Natural Resources
College of Arts and Sciences
College of Earth, Ocean and Environment
College of Education and Human Development
College of Engineering
College of Health Sciences
Graduate College
Honors College

There are also five schools:

Joseph R. Biden, Jr. School of Public Policy and Administration (part of the College of Arts & Sciences)
School of Education (part of the College of Education & Human Development)
School of Marine Science and Policy (part of the College of Earth, Ocean and Environment)
School of Nursing (part of the College of Health Sciences)
School of Music (part of the College of Arts & Sciences)