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Climate change is causing Antarctica's snow to turn green, study says - CBS News
As the climate warms, scientists expect more and more of the snowy desert to turn bright green.
In coastal Antarctica, some snow isn't white — it's green. And while small amounts of the green snow have been visible for years, it's starting to spread across the continent because of climate change. According to a study published Wednesday in the journal Nature Communications, the vibrant color is caused by microscopic algae blooming across the surface of the snow. Using satellite data and fieldwork observations, a team of researchers at the University of Cambridge and the British Antarctic Survey have created the first large-scale map of the green algae and predicted the future spread of the bizarre snow. Green snow appears along the Antarctic coast, growing in "warmer" areas, where the average temperatures reach just above freezing in the summer. Although the individual algae are microscopic, when they grow at scale, the green snow can even be seen from space. For the study, the team combined on-the-ground research from two summers in the Antarctic Peninsula with images from the European Space Agency's Sentinel 2 satellite taken between 2017 and 2019. In total, the team identified over 1,600 separate algal blooms on the snow surface. Lead author Matt Davey samples snow algae on Lagoon Island, Antarctica. Sarah Vincent The team found that the distribution of green snow algae is strongly influenced by marine birds and mammals, because their excrement works extremely well as fertilizer. Over 60% of blooms were found near penguin colonies, and others were found near birds' nesting sites. "This is a significant advance in our understanding of land-based life on Antarctica, and how it might change in the coming years as the climate warms," lead author Dr. Matt Davey of the University of Cambridge said in a press release. If bird populations are strongly affected by climate change, as they likely will be, the algae could lose key sources of nutrients. But the results of the study indicate that green snow will massively spread as global temperatures rise. That's because in order to flourish, the organisms need an available supply of water. Temperatures on the peninsula where the green snow is found have risen dramatically in recent decades, increasing the amount of water available. As the planet warms and more of Antarctica's snow melts, the algae will spread, the scientists said. And while some algae will be lost to areas that lose snow altogether, much more will be gained. A photograph showing Anchorage Island dominated by green algae starting to melt out from beneath surface snow on January 26, 2018. Nature Communications "As Antarctica warms, we predict the overall mass of snow algae will increase, as the spread to higher ground will significantly outweigh the loss of small island patches of algae," said co-lead author Dr. Andrew Gray, of the University of Cambridge and the University of Edinburgh. It's unclear how the spreading algae will affect the planet. It plays a key role in cycling nutrients and pulling carbon dioxide from the atmosphere through photosynthesis, Davey said, but also darkens snow, and absorbs more heat from the sun. The amount of algae found by the team creates a carbon sink that absorbs about 500 tons of carbon each year, the equivalent of about 875,000 average car journeys in the U.K., researchers said. The amount of algae found is actually a conservative estimate, because the satellite was only capable of picking up green algae, missing its red and orange counterparts. "The snow is multi-colored in places, with a palette of reds, oranges and greens — it's quite an amazing sight," Davey said.
In just 16 years, Antarctica and Greenland have lost enough ice to fill Lake Michigan - CBS News
The two landmasses have lost about 5,000 gigatons of ice in the last decade and a half, which could fill around 2 billion Olympic-sized swimming pools.
Antarctica and Greenland have lost thousands of gigatons of ice in the last 16 years alone. According to new data from NASA, that ice melt has contributed to more than half an inch of sea level rise around the world. Collectively, Antarctica and Greenland lost more than 5,000 gigatons of ice over the last decade and a half — more than enough to fill Lake Michigan. One gigaton is the equivalent of one billion metric tons, which could fill 400,000 Olympic-sized swimming pools alone, NASA said in a press release. According to a paper published Thursday in the journal Science, the two regions have collectively been responsible for .55 inches of sea level rise between 2003 and 2019 — roughly a third of total global sea level rise during that time. The data come from NASA's Ice, Cloud and land Elevation Satellite 2 (ICESat-2). Launched in 2018, it is the "most advanced Earth-observing laser instrument NASA has ever flown in space," in combination with data from its predecessor, ICESat, which gathered data from 2003 to 2009. (Top) Mass change for Antarctica. (Bottom) Mass changes at the grounding line. NASA ICESat and ICESat-2 "If you watch a glacier or ice sheet for a month, or a year, you're not going to learn much about what the climate is doing to it," said Ben Smith, a glaciologist at the University of Washington and lead author of the paper. "We now have a 16-year span between ICESat and ICESat-2 and can be much more confident that the changes we're seeing in the ice have to do with the long-term changes in the climate." According to the data, per year, Greenland's ice sheet lost an average of 200 gigatons of ice, and Antarctica's lost an average of 118. Using information from both missions, researchers found not only the amount of ice melted but one of the major causes. Ice shelves around Antarctica act as barriers to slow the rate of ice loss — they don't contribute to sea level rise because they are already floating — but, as those barriers melt into warming oceans, the rate of ice loss increases. "It's like an architectural buttress that holds up a cathedral," said Helen Amanda Fricker, co-author and glaciologist at Scripps Institution of Oceanography at the University of California San Diego. "The ice shelves hold the ice sheet up. If you take away the ice shelves, or even if you thin them, you're reducing that buttressing force, so the grounded ice can flow faster." While a significant amount of Antarctica's ice loss came from floating ice shelves, through iceberg calving and melting from warm water, the majority of Greenland's loss was due to surface melting and runoff. In Greenland, coastal glaciers have thinned dramatically, mostly due to warmer summer temperatures. (Top) Mass change (m ice equivalent per year). (Bottom) Mass changes around the margin. NASA ICESat and ICESat-2 NASA's new data is consistent with previous studies on sea levels rise, but the satellites' lasers give researchers a much more detailed analysis of how polar ice is changing over time. While East Antarctica has actually seen a small uptick in its amount of ice, that improvement has been far outweighed by the huge losses in West Antarctica, where the ocean has rapidly warmed. "The rise in a single year is in itself not concerning," Alex Gardner, co-author and glaciologist at NASA's Jet Propulsion Laboratory, told CBS News on Friday. "What is concerning is that this will continue every year for the foreseeable future, adding up to considerable sea level rise over the next 80 years. By 2100 we are expecting 2,3, or maybe 4 feet of sea level rise." Rising sea levels are expected to affect millions of people living in coastal cities around the world. "This matters because civilization has evolved around coastal cities where considerable infrastructure is located near present sea levels," Gardner continued. "When there is a high-tide event or passing storm they can cause considerable damage to property. These damages will be greatly amplified as sea level continues to rise and will require municipalities and counties to make hard choices about what infrastructure to invest in to try and save and what infrastructure should be abandoned." NASA Mission Maps 16 Years of Ice Loss by NASA Goddard on YouTube