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Dark Algae Accelerates Greenland Ice Sheet Melting

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Greenland ice sheet algae absorb light and accelerate melting

Laura Halbach

Dark algae growing on the surface of the Arctic ice sheet are likely to expand future coverage, and tend to exacerbate melting, sea level rise and warming.

“These algae are not a new phenomenon.” James Bradley At the Institute of Oceanography in Marseille, France. “But if they bloom more intensely or the flowers bloom more widely, this is an important thing to consider in future projections of sea level rise.”

Greenland's ice sheets, which cover most of the island, are rapidly melting due to rising temperatures, making them the biggest contributor to sea level rise worldwide.

ancylonema Algae under a microscope

Natural Communication

ancylonema Algae species bloom in patches of ice called ablation zones, which are exposed as snow lines recede to the ice sheet every summer. Flowers darken the ice, reduce its reflectivity, absorbing more heat, thereby increasing melting in these regions by an estimated 10-13%.

To better understand this feedback loop, Bradley and his colleagues gathered ancylonema Samples from the southwest tip of the ice sheet were examined for cells using advanced imaging techniques.

The results reveal that algae are highly adapted to malnutritional conditions and suggest that they can invade ice at high elevations with low nutrients.

Global warming already causes snow lines to increase altitude over time, exposing more ice. Ice algae should add yet another layer to these interactions and explain it in future climate forecasts.

“We have been studying glacial algae flowers for several years, and one of the biggest questions that remains is that we can grow to such high numbers in such undernourished ice.” I say that. Christopher Williamson At the University of Bristol, UK, where he was not involved in the project. “A big part of understanding this puzzle is the amount of nutrients needed for glacial algae cells and whether it can efficiently take and store rare nutrients available in the system. This research is cutting edge. They do an amazing job of demonstrating these things using the methodology of

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Source: www.newscientist.com

The impact of the melting Greenland Ice Sheet on ocean currents

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Climate change affects our planet and our lives in many ways. Dry the atmosphere To Increase in home runs Climate change accelerates glacial melt with each Major League Baseball season. Greenland Ice Sheet The land ice mass that covers about 80% of Greenland. When glaciers melt, icebergs form, a process called “iceberg formation.” Glacier collapse Recent climate change has increased the rate at which icebergs are flowing from the Greenland Ice Sheet into the North Atlantic.

Scientists have found that in the past, large increases in the rate of glacial collapse have disrupted important ocean current systems in the Atlantic Ocean. Atlantic Meridional Gyre Or as the AMOC, it carries warm water north and cold water south, affecting global temperatures and moving nutrients across the Atlantic Ocean, meaning that disrupting the AMOC could change the climate and destabilize marine ecosystems. Recently, scientists conducted a study to determine whether the current increase in glacier collapse could disrupt the AMOC.

For this study, the researchers developed a method to quantify glacial runoff during past periods of increased glacial collapse in the North Atlantic that disrupted the AMOC. Heinrich Event They began by looking at present-day glaciers in the North Atlantic and the Arctic. As icebergs break up, they deposit sediment. This sediment includes sand and rocks from the land below the ice sheet, as well as the remains of organisms that lived on the ice sheet. When the icebergs melt at sea, the sediment is released and sinks to the ocean floor.

Scientists observed modern glaciers melting and measured the average amount of sediment, by volume, that they released. Using this average, the researchers estimated how much ice was released during past Heinrich events, based on the amount of sediment that was deposited on the floor of the North Atlantic Ocean.

Scientists used this method to estimate the total amount of ice lost during 10 Heinrich events (the last of which) that occurred over the past 140,000 years. Glacial Cycle Previous scientists had determined the duration of Heinrich events, which allowed the researchers to estimate the ice runoff rate during each event. The researchers compared their estimated runoff rates to current ice runoff rates and found that current ice runoff rates are similar to those of previous mid-sized Heinrich events that disrupted the AMOC. However, the scientists who conducted the study also noted that the AMOC is currently stable.

The researchers suggested two factors that could help explain why the current increase in glacial collapse is not disrupting the AMOC as much as it has in the past. First, the researchers think that the AMOC was stronger when the current glacial runoff rate began to increase than it was at the start of past Heinrich events, which may make the current AMOC more resistant to disruptions. Second, each of the 10 Heinrich events the scientists used in their study lasted about 250 years, while the faster glacial collapse seen today may have been due to a slowdown in the early Heinrich events. It began in recent decades They suggested that AMOC collapse could only occur after a longer period of increased glacier calving than has happened previously.

If the rate of glacial calving continues to increase by the time the AMOC collapses, the size of the Greenland Ice Sheet may limit its influence on the AMOC. The researchers noted that if the Greenland Ice Sheet continues to melt at its current rate, the rate of calving will slow before 250 years have passed. The icebergs that caused the Heinrich events in the last glacial cycle broke off from a much larger ice sheet. Laurentide Ice Sheet It no longer exists.

The scientists who conducted the study said that freshwater runoff from the melting Greenland Ice Sheet could also disrupt the AMOC, but its impact would be less severe than ice runoff. However, they noted that freshwater runoff is likely to increase as glacial collapse slows in the coming decades, which could have unpredictable consequences. The researchers suggested that the scientific community should continue their work to model the impacts of a melting Greenland Ice Sheet as accurately as possible, because, in their words, “the fate of the AMOC remains uncertain.”


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Source: sciworthy.com

Hot water leaking beneath Antarctic ice sheet may quicken melting

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Aerial photo of the Antarctic ice sheet

David Vaughn/BAS

Antarctica’s melting ice sheet could retreat faster as warmer ocean water invades underneath it, and rising ocean temperatures could trigger a “runaway” feedback effect that pushes warm water further inland, melting even more ice and accelerating sea-level rise.

As the climate warms, the future of Antarctica’s vast ice sheet remains uncertain, and predictions vary widely about how quickly it will melt and therefore how much it will contribute to sea-level rise. One dynamic that researchers have only recently begun to recognize as a key factor is the intrusion of warmer ocean water beneath the ice.

“The mechanisms of invasion are much more powerful than we previously understood.” Alexander Bradley At the British Antarctic Survey.

Such intrusions are driven by density differences between the freshwater flowing out from beneath the ice sheet and the warmer waters where the ice meets the sea floor, known as the grounding line. They are difficult to observe directly because they occur hundreds of meters beneath the ice, but simulations suggest that in some places the warm waters could extend several kilometers inland.

One model by Alexander Lovell Researchers from the Georgia Institute of Technology in Atlanta found that widespread ice-sheet intrusion could add heat from below, lubricating ice flow along bedrock and more than doubling ice loss from the ice sheet.

Bradley and his colleagues Ian Hewitt Using their model, Oxford researchers explained how the shape of cavities in the ice changes as the ice melts, altering how ocean water flows in.

The researchers found that once ocean water reaches a certain temperature threshold, ice from the ice sheet melts faster than it can be replaced by outflowing ice. If this cavity grows larger, more water could flow under the ice sheet and penetrate further inland, creating a so-called “runaway” positive feedback effect.

“Small changes in ocean temperature lead to dramatic changes in how far warm water can intrude,” Bradley said. The ocean warming needed to cause this effect is within the range expected this century, he said, but models cannot yet predict it for specific ice sheets, and not all ice sheets are equally susceptible to such intrusions.

“This positive feedback could lead to much more intrusion than we thought,” Lovell says. “Whether that’s a tipping point that leads to unrestrained intrusion of ocean water beneath the ice sheet is probably a stretch.”

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Source: www.newscientist.com