Scientists Find a Link Between Rapidly Melting Arctic Ice and Ocean Acidification – Watts Up With That?

Discovery highlights dual threats to climate and the survival of plants, shellfish, coral reefs and other marine life

A peer-reviewed publication

UNIVERSITY DELAWARE

An international team of researchers has sounded a new alarm about the chemical change of the western part of the Arctic Ocean after detecting acidity levels rising three to four times faster than seawater in the Arctic Ocean. other places.

The team, including University of Delaware’s marine chemist Wei-Jun Caialso identified a strong correlation between the rapidly increasing rates of thaw in the region and the rate of ocean acidification, a dangerous combination that threatens the survival of plants, shellfish, and coral reefs. and other marine organisms and biological processes throughout the planet’s ecosystems.

The new study, published on Thursday, September 30 in Science‘s leading magazine American Association for the Advancement of Scienceis the first analysis of Arctic acidification to include data from more than two decades, spanning from 1994 to 2020.

Scientists have predicted that by 2050 – if not earlier – the Arctic sea ice in this region will cease to exist after increasingly warm summers. As a result of this retreat of sea ice each summer, the ocean’s chemistry becomes more acidic, with no persistent ice cover to slow or minimize the advance.

That creates life-threatening problems for the diverse populations of marine life, plants and other living things that depend on a healthy ocean for survival. For instance, crabs live in rough shells built from calcium carbonate common in ocean water. Polar bears rely on healthy fish populations for food, fish and seabirds rely on plankton and plants, and seafood is a staple of many people’s diets.

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

First, a quick refresher course on pH levels, which indicates how acidic or alkaline a given liquid is. Any liquid containing water can be characterized by its pH level, which ranges from 0 to 14, with pure water being considered neutral with a pH of 7. All levels below 7 are acidic, all levels greater than 7 are basic or alkaline, with each full step representing a tenfold difference in hydrogen ion concentrations. Examples of acids include battery acid, tested at pH 0, stomach acid (1), black coffee (5), and milk (6.5). Tilt is basically blood (7.4), baking soda (9.5), ammonia (11) and drain cleaner (14). Sea water is usually alkaline, with a pH value of around 8.1.

QuitProfessor Mary AS Lightship in School of Marine Science and Policy at UD’s College of Earth, Oceans and Environment, published significant research into the chemical changes of the planet’s oceans and this month completed a voyage from Nova Scotia to Florida, was the lead scientist of the 27 people on board the research vessel. Work, powered by National Oceanic and Atmospheric Administration (NOAA), which includes four study areas: East Coast, Gulf of Mexico, Pacific Coast, and Alaska/Arctic region.

The new study in the journal Science includes UD postdoctoral researcher Zhangxian Ouyang, who was on a recent trip to collect data in the Chukchi Sea and the Canadian basin in the Arctic Ocean.

The first author of the publication is Di Qi, who works with Chinese research institutes in Xiamen and Qingdao. Also collaborating with this publication are scientists from Seattle, Sweden, Russia, and six other Chinese research institutions.

“You can’t just go it alone,” Cai said. “This international collaboration is important for long-term data collection over a large area in the far seas. In recent years, we have also collaborated with Japanese scientists as access to water in the Arctic has become even more difficult over the past three years due to COVID-19. And we always have European scientists involved.”

Cai said both he and Qi were confused when they first looked at Arctic data together during a conference in Shanghai. The acidity of water increases 3-4 times faster than seawater in other places.

That is really great. But why did it happen?

Cai quickly identified a prime suspect: the increasing melting of sea ice during the Arctic summer.

Historically, sea ice in the Arctic has melted in shallow margins during the summer. That started to change in the 1980s, Cai said, but waxes and wanes in cycles. Over the past 15 years, ice melt has accelerated, moving into the depths to the north.

For some time, scientists thought that melting ice could create a promising “carbon sink” where carbon dioxide from the atmosphere would be sucked into cold, carbon-starved waters hidden under the ice. That cold water would contain more carbon dioxide than warmer water could, and could help offset the effects of increased carbon dioxide elsewhere in the atmosphere.

When Cai first studied the Arctic Ocean in 2008, he found that the ice had melted beyond the Chukchi Sea in the region’s northwest corner, all the way to the Canadian Basin – well beyond its typical range. He and his colleagues found that fresh water did not mix with deeper water, which would dilute the carbon dioxide. Instead, surface water absorbs carbon dioxide until it reaches levels similar to those in the atmosphere and then stops collecting it. They reported this result in an article in the journal Science in 2010.

They know that will also change the pH of the Arctic water, reducing the alkalinity of the seawater and reducing its resistance to acidification. But how much? And how long? It took another decade for them to gather enough data to draw proper conclusions about long-term acidification trends.

Analyzing data collected between 1994 and 2020 – the first time such a long-term perspective is possible – Cai, Qi and their colleagues discovered an unusual increase in acidification and closely correlated with the increasing rate of ice melt.

They show that sea ice melt is the main mechanism to explain this rapid pH drop, because it changes the physical and chemical properties of surface water in three basic ways:

• The water under the sea ice, which is starved of carbon dioxide, is now exposed to atmospheric carbon dioxide and can absorb carbon dioxide freely.
• Seawater mixes with meltwater lightly and cannot enter deeper water, which means that carbon dioxide taken from the atmosphere is concentrated at the surface.
• Dissolved water dilutes the concentration of carbonate ions in seawater, weakens the ability of carbon dioxide to neutralize carbon dioxide to bicarbonate, and rapidly lowers the pH of seawater.

Cai said more research is needed to further refine the mechanism and better predict future changes, but the data so far suggest far-reaching effects of climate change.

“If all multi-year ice were replaced by first-year ice, the alkalinity would be lower and the buffer capacity would be lower and acidification would continue,” he said. “By 2050, we think all the ice will be gone by summer. Some papers predict that will happen by 2030. And if we follow current trends for another 20 years, the summer acidification will be really strong.”

No one knows exactly what that will do to the creatures and plants and other living things that depend on fresh seawater.

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

JOURNEYS

Science

DOI

10.1126 / science.abo0383

ARTICLE TITLE

Climate change drives rapidly degrading acidification in the Arctic Ocean from 1994 to 2020

ARTICLE PUBLICATION DATE

September 29, 2022

From EurekAlert!