This year, the Arctic was chosen as one of the nominees for Oxford University Press’s Place of the Year. But why is this location so significant? The Arctic sea ice has been seen to be in steady retreat since about 1950, a retreat which has recently sped up with an additional factor of thinning. In summer now there is only a quarter of the volume of ice that there was in summer in 1980. This process of sea ice retreat and thinning, illustrated by the “Arctic Death Spiral,” shows every sign of continuing, so that the Arctic will be ice-free for part of the year.
Obviously we view this as a product of global warming, but why should it concern us in other ways? The retreat of the ice causes other feedbacks which are a threat to the entire world. Here are some of the effects.
As the ice retreats, a white surface which reflects most solar radiation is replaced by a dark surface (open sea) which reflects less than 10% of the solar radiation falling on it. The extra absorbed radiation makes the climate of the whole world warm faster; it has been estimated that along with the snow retreat which is also occurring, this is equivalent to adding 50% to the warming effect of adding CO2 alone.
Greenland ice sheet
The warm air around the Arctic Ocean in summer causes the surface of the Greenland ice sheet to start to melt, which never used to happen before the 1980s. The ice sheet is now losing 300 cubic kilometers of water per year, which contributes to global sea level rise, and in fact is now the biggest single factor in the speed-up of global sea level rise.
There is a threat from the large amount of methane gas which at the moment is held in seabed sediments under the Russian continental shelves in the Arctic Ocean. The gas is sealed in by permafrost on the seabed, but as the water warms up this permafrost melts and we may have a huge pulse of methane gas released to the atmosphere. This is a powerful greenhouse gas and could cause an immediate warming of several tenths of a degree.
The loss of ice production in the Arctic, particularly the Greenland Sea, reduces the strength of the thermohaline circulation, the slow circulation of water in the Atlantic which used to include sinking underneath pack ice in the Greenland Sea. With no ice growing there anymore, the sinking stops and the current slows. This means that less warm water is carried out of the Gulf of Mexico and Caribbean towards northern Europe. Europe cools down – or warms up more slowly – but the Gulf water warms up faster, increasing the intensity of hurricanes.
There is evidence that the extreme weather events of the past few years are due to a slowdown in the jet stream, the fast westerly wind that separates polar from tropical air masses. As the Arctic warms faster than the tropics the wind slows down and develops big lobes, which funnel polar air down to lower latitudes and nearby tropical air to higher latitudes. This gives alternating extremely hot and cold regions, right in the zones where crop production is greatest – a serious threat to our food.
Everything on Earth is dependent on something else, and this is particularly true of the Arctic. So we should be thoroughly alarmed by the loss of ice and take it as a signal that we must do everything in our power to slow down the warming of the planet.
Featured image credit: “sunset-climate-change-iceberg” by geralt. CC0 via Pixabay.