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The warming of the Arctic Ocean now reaches to its deepest waters<\/p>\n
Mozgova\/Shutterstock<\/p>\n<\/p>\n
Warmer Atlantic water from near Greenland is heating up the depths of the Arctic Ocean<\/a>, which was previously thought of as one of the few places not significantly affected by climate change.<\/p>\n The sea ice on top of the Arctic Ocean has shrunk by about 40 per cent in four decades, due largely to the effect that atmospheric warming has on the surface of the ocean. Now researchers from the Ocean University of China have analysed the latest measurements taken using icebreaker ships to estimate warming at the bottom of the ocean.<\/p>\n In one of the ocean\u2019s two major basins \u2013 the Eurasian basin \u2013 the waters between 1500 and 2600 metres deep have warmed by 0.074\u00b0C since 1990.<\/p>\n While that doesn\u2019t sound like much, it represents the transfer of almost 500 trillion megajoules of energy. If that amount of energy were present at the surface, it could melt as much as a third of the minimum sea ice extent.<\/p>\n \u201cThe deep ocean is much more active than what we thought,\u201d says Xianyao Chen<\/a>, a member of the research team. \u201cI thought the deep ocean could be warming, but not so fast.\u201d<\/p>\n An underwater mountain range running between Greenland and Siberia divides the Arctic Ocean into two basins. While the Amerasian basin is largely walled off from the Pacific by the shallow Bering Strait, an extension of the Atlantic Meridional Overturning Circulation<\/a>, or AMOC, brings warm Atlantic water northwards along the coast of Scandinavia and into the upper layers of the Eurasian basin. As seawater freezes in the winter, the salt in it is ejected from the crystals. This forms dense water that sinks to the depths, taking some of the warm water from the Atlantic with it.<\/p>\n The geothermal heat<\/a> of Earth also warms deep water in the Eurasian basin.<\/p>\n Previously, these warming processes have been offset by an influx of cold deep water from the basin immediately to the east of Greenland. But as the Greenland ice sheet melts, more freshwater has entered the Greenland basin. This has slowed the sinking of cold, salty water to the deep and helped raise the deep water temperature in the Greenland basin from -1.1\u00b0C to -0.7\u00b0C \u2013 one of the fastest warming rates in the deep ocean. As a result, the movement of Greenlandic deep water into the Arctic Ocean no longer cancels out the geothermal bottom heat and sinking of warm Atlantic water.<\/p>\n \u201cThe warming of the Greenland basin has extended to the Arctic,\u201d says Ruizhe Song<\/a>, part of the research team.<\/p>\n