![]() ![]() The researchers estimated the ages of the shorelines by collecting ancient shells and tiny fragments of penguin bones, before analyzing the ancient biomatter with radiocarbon dating. The reality of climate change: 10 myths busted Antarctica: The ice-covered bottom of the world (photos) By measuring the ages and heights of nearly two dozen shorelines, the scientists hoped to discover how quickly ice disappeared from the land before advancing again. Ice weighs down land, so as some of that frozen weight melted and drained into the sea toward the end of the last ice age (around 11,500 years ago) the land rebounded to reveal shorelines that were previously hidden beneath the waves. To compare the glaciers' melt rates today with those of the distant past, scientists looked for clues on Antarctic beaches close to where the glaciers terminated at the ocean. If the entirety of the West Antarctic Ice Sheet were to break up and melt into the sea, it would elevate global sea levels by approximately 11 feet (3.4 meters). Additionally, this melt from below weakens the glaciers and makes them more prone to surface fractures, which could spread across the entire ice sheet, and potentially cause it to shatter. This warm water isn't just melting the glaciers where they extend into the Amundsen Sea, but it is also whittling away at them from underneath, unpinning them from their main anchoring points located to the north. It seems even in Antarctica we can identify human impacts on climate processes that are likely to have been operating for thousands of years.As the sea-facing ends of the glaciers are positioned above a bowl-like ocean basin, both glaciers are exposed on their undersides to currents of warm, dense, salty water. Other studies have shown us that the way the SAM has changed over recent decades has an anthropogenic footprint. The researchers think this is due to large-scale changes in the way the wind circulates over Antarctica – the so-called Southern Annular Mode (SAM). ![]() Over the past 50 or so years the robust cycle of growth and decay in the Mertz glacier has broken down. David Stanley, CC BYĪs they drift away these huge icebergs create their own habitat cooling the seas and freshening the waters, and also seeding the oceans with iron which means more algae and plankton at the bottom of the food chain in remote locations such as South Georgia, where icebergs run aground and die. Chicks growing up near a massive iceberg may starve and die and some entire colonies may become unviable. When still close to shore these giant bergs are bad news for penguins, who suddenly have to travel much further – around the iceberg – to find open sea, and their food. It took two months for C28 to reach the deep water before it shattered into two pieces ( C28A and C28B since you ask) both still massive, and both went on to spawn further icebergs as they fractured into ever smaller pieces over the next few years. Very large icebergs get identifying codes this one became C28 as it was the 28th large iceberg from this sector of Antarctica. Given that the glacier is advancing about 1 km per year this means a super-iceberg tens of kilometres in length has regularly formed in this region.ī09B collides with the Mertz Glacier Tongue, causing it to break off and form a new iceberg. What they found is that every 70 or so years the Mertz polynya is absent for tens of years. Neal Young / Australian Antarctic Division It is quite an elegant way to investigate glacier flow.Ī massive iceberg (right) drifts slowly towards the Mertz tongue. If the sediment is dominated by species which live in the sea ice, then the polynya and the glacier tongue were absent. ![]() The proxies tell us which species of plankton dominated the region in a particular period: if the sediment is dominated by species which live in open water then they can infer that the polynya existed and so the Mertz Glacier had a long tongue extending north. What they did was take a core sample of sediment from the sea bed in the lee region (the red star in the above images) and look back in time using climate proxies such as the titanium content – which can be considered a proxy for the how much of the sediment comes from the land. The glacier tongue (blue) in summer and winter. This glacier forms one of these fingers of ice reaching out from the continent and the polynya in its lee can be up to 6,000 square kilometres. A new research article in the journal Nature Communications by a French team working in Antarctica has looked at the history of the polynya in the lee of the Mertz Glacier going back 250 years. ![]()
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