Climate Change | The layer of cold water on the ocean floor is getting warmer, it also has a hand in climate change

File Photo Southampton/Cambridge: Our new research in the Antarctic shows that the critical layer of cold water on the ocean floor that spins the globe and helps maintain the ocean’s ability to absorb most of the atmospheric heat and greenhouse gas emissions It’s getting hotter and shrinking. Much of this is the result of man-made climate change, which is melting the Antarctic ice sheet and disrupting the complex system that controls this movement. The ocean absorbed about 30% of the carbon dioxide but it appears that, as far as the last 30 years are concerned, a natural cycle may be partly responsible for the observed changes. The ocean has absorbed more than 90% of the excess heat produced by humans and about 30% of the excess carbon dioxide since the beginning of the industrial era. This has greatly reduced the effect of climate change on the surface of the earth where we live. Most of the exchange of gases and heat between the atmosphere and the ocean occurs through complex vertical movements of the waters around Antarctica in the Southern Ocean. One of the biggest drivers of this vertical activity is what oceanographers call Antarctic floor water. Around the Antarctic coastline, seawater near the freezing point is exposed to very cold air and freezes into sea ice, which leaches out the salt and Absorbs fresh water to leave cold, salty and dense water. Most of this dense water originates in just a few places around Antarctica. In these places, wind blowing from the icy continent continually pushes newly formed sea ice away from the surrounding ice sheets to create areas of open water called polynyas. These polynya ice factories produce vast amounts of cold and salty water that flows like a submarine spring from the continental slope of Antarctica towards the ocean floor. A decrease of more than 20% in the past 30 years. Upon reaching there, Antarctic floor water, the world’s deepest and densest water mass and the largest water reservoir of its kind worldwide, expands to remain isolated from the atmosphere for hundreds or even thousands of years. stores carbon. As Antarctic floor water moves northward along the ocean floor, it drives the Great Ocean Circulation System, currents that redistribute heat, carbon and nutrients around ocean basins and control global climate . Our new research used observations from ships and satellites to find that the volume of bottom water in the Weddell Sea, the Atlantic region of the Southern Ocean and one of the largest producers of this water mass, has decreased by more than 20% over the past 30 years. There is a shortage of more. This caused the deep Weddell Sea to warm four times faster than the global average. Natural variability in wind and sea ice is also important. Our evidence suggests that the weakening of offshore winds in this region is responsible for the shrinking of polynyas and the reduction of cold, dense, salty water that fills the Antarctic floor and is responsible for global warming. The ocean drives the conveyor. This can slow down the deep overturning circulation, with deep implications for the climate system. Previous studies have linked the slowing of the global ocean conveyor with the loss of cold, dense water in the Southern Ocean due to the rise of meltwater from the ice sheets. Although human-caused climate change is important, our new research suggests that natural variability in wind and sea ice is also important. What’s up with the wind in the Weddell Sea? Weaker winds blowing offshore in the southern Weddell Sea over the past 30 years have limited the size of coastal polynyas, which in turn have produced less sea ice. We found that this change in wind appears to be linked to surface temperature changes in the tropical Pacific during the same period, which is part of a natural cycle similar to El Niño, known as the Interdecadal Pacific Oscillation. May be part of a long natural cycle in which sea surface temperatures in the tropical Pacific are strong enough to influence local air pressure and even wind on both sides of the Antarctic Peninsula. This means that the trend of the Weddell Sea winds and the resulting Antarctic bottom water build-up over the past 30 years may also be part of a longer natural cycle. If it’s natural, should we stop worrying? Ship-based observations have helped show us that the underwater layer around Antarctica has been warming and thinning everywhere for decades. In areas other than the Weddell Sea, both recent model predictions and observations suggest that this can be explained by increased melting of freshwater from the Antarctic ice sheets, inhibiting the formation of salty and dense water that would otherwise sink. Will go A similar change was found in the bottom layer of water in the Weddell Sea, although the ice sheets here are not melting as rapidly as elsewhere in the Antarctic. This is mainly because the polynya sea ice factory near the coast usually keeps the warm waters of the Southern Ocean at bay. Although our study suggests that changes in the Weddell Sea are a result of natural variability in the Earth system, they are also part of an Antarctic-wide trend that is not clearly attributable to natural causes. In fact, the shrinking of the waters below is in line with scientific predictions about the melting ice sheet. Satellite observations have shown a steady decrease in the mass of the ice sheet since 2002. Current knowledge of physics to understand future climate and models are one of the best tools to better study present and past conditions. But their representations of many important processes, such as Antarctic bottom water formation, are often incomplete. And so there is a need for continued research to advance our understanding of how the Earth system works and to refine projections of the future. ALSO READ Systematic efforts needed to slow global warming More and more evidence indicates that the Antarctic ice sheet is vulnerable to a warming climate and melting of this large reservoir of ice could lead to overturning across the global ocean Circulation will be obstructed. This will disrupt the climate and accelerate sea level rise globally. As scientists who study the complex relationship between the ocean, ice sheet and atmosphere around Antarctica, we hope that refining our understanding of the Earth system and future climate projections will help inform decision makers. Will get Systematic efforts are needed to urgently reduce greenhouse gas emissions and slow the pace of global warming. (agency)