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Faster than forecast - Melting Arctic
Abrupt climate change in the Arctic
Ice covers 10 percent of Earth's surface and helps moderate the planet's temperature. Glaciers, sea ice and ice sheets around the world are melting at an alarming rate. Much faster than climate models had predicted, like what Peter Wadhams, expert on ocean and ice physics, discusses in the video clip above. Climate models fail to interpret the real climate system because they ignore nonlinear dynamics, like key carbon cycle feedbacks and tipping points, crucial to the real system.
The Arctic (North of 60° N) is a key strategic region of global importance. Changes in the Arctic impact Earths energy balance, cloud formations, global wind patterns and ocean currents, release of methane, sea level rise, phytoplankton blooms and much more. As seen in the image below.
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| Component state variables and dynamic processes operating in the Arctic. There are strong couplings, feedbacks and nonlinear behaviors arising from their interactions, which together define the Arctic system. Source: Arctic System Synthesis, 2018 |
A recent study published by NASA shows how, since 1958, Arctic sea ice cover has lost about 66% of its thickness, averaged across the region at the end of summer. Old ice has shrunk more than 2 million square kilometres and today 70% of the ice cover consist of ice that forms and melts within a single year. Thinner, weaker seasonal ice is much more vulnerable to weather than thick ice and can easily be broken apart by storms.
That's very bad news for our planet as darker ocean waters absorb more sunlight and triggers further warming. Melting sea ice has already contributed to about 25% of current warming but could add double that amount when the Arctic ocean starts becomes ice free in summer. That's a very strong reinforcing feedback process that accelerates warming which in turn accelerates further ice loss and so on. While in theory, with some sort of risky geoengineering, it would be possible to reverse this trend I really doubt we can do much to stop it. We can't even stop our greenhouse gas emissions from growing every year. No, its too late for Arctic sea ice, what we see now is a death spiral.
Warming in the Arctic occurs much faster than at lower latitudes, a process known as Arctic Amplification. Arctic temperatures have increased at least 3 times the rate of mid-latitude temperatures relative to the late 20th century, due to multiple reinforcing feedbacks. Even if global temperature increases are contained to +2° C by 2040, Arctic monthly mean temperatures in fall will increase by +5° C. The Arctic is very likely to be sea ice free during summer before 2040, and probably much sooner than that. Not like the IPCC report says, once in every hundred years.
This will impact mid-latitude, like Europe, weather events by causing the jet stream to slow down and become more meandering which causes more persistent weather patterns as high or low pressure weather systems to get stuck in one place for an extended duration. Like what we saw this summer in Scandinavia with persistent heat wave, drought and forest fires i Sweden.
We have also detected a slowing down of the Atlantic meridional overturning circulation (AMOC) during the past 150 years since the little ice age, and that enhanced freshwater fluxes from the Arctic and Nordic seas weakened Labrador Sea convection and thus the AMOC. Its been suggested that the lack of a subsequent recovery may have resulted from hysteresis (i.e., instability of thermohaline circulation) or from 21st century melting of the Greenland Ice Sheet.
Another recent Nature article improved a sea surface temperature proxy for AMOC strength. Their proxy AMOC fingerprint consists of a cooling in the subpolar gyre region due to reduced heat transport, and a warming in the Gulf Stream region due to a northward shift of the Gulf Stream, indicating that AMOC has been steadily weakening since around 1950, strengthened shortly during the 1990s and 2000s, then weakened again. In the short term this could cause a small cooling effect in western Europe while warming the ocean waters in the gulf of Mexico, southeast Americas. Not mentioned in the latest IPCC report.
Last time Earth went through an interglacial period, and global temperatures were less than 1C warmer than today, sea level rose to +6-9 meters and extreme storms were common. Sea level rise has accelerated as ice sheet loss on Greenland and West Antarctica has accelerated. Also not accounted for in the latest IPCC report.
Huge slabs of Arctic permafrost are slumping and disintegrating, sending large amounts of carbon-rich mud and silt into streams and rivers. Permafrost decay is affecting 52,000 square miles in Canada—an expanse the size of Alabama. According to researchers with the Northwest Territories Geological Survey, the permafrost collapse is intensifying. Similar large-scale landscape changes are evident across the Arctic including in Alaska, Siberia and Scandinavia, the researchers wrote in a paper published in the journal Geology. Arctic permafrost caps vast amounts of old, geologic methane (CH4) in subsurface reservoirs. Thawing permafrost opens pathways for this CH4 to migrate to the surface. The concentration of methane in the atmosphere has risen sharply - by about 25 teragrams per year since 2006. Sub sea methane clathrates could also be seeping out. None of these feedbacks are included in IPCC climate models.
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| Melting permafrost is altering the landscape in northern Canada on a grand scale. Credit: Wikimedia |
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