Source: PhysOrg.com
Sea ice cover in Antarctica shrank rapidly to a record low in late 2016 and has remained well below average. But what’s behind this dramatic melting and low ice cover since?
Our two articles published earlier this month suggest that a combination of natural variability in the atmosphere and ocean were to blame, though human-induced climate change may also play a role.
What happened to Antarctic sea ice in 2016?
Antarctic sea ice is frozen seawater, usually less than a few metres thick.
It differs from ice shelves, which are formed by glaciers, float in the sea, and are up to a kilometre thick.Sea ice cover in Antarctica is crucial to the global climate and marine ecosystems and satellites have been monitoring it since the late 1970s. In contrast to the Arctic, sea ice around Antarctica had been slowly expanding (see figure below).
However, in late 2016 Antarctic sea ice dramatically and rapidly melted reaching a record low. This piqued the interest of climate scientists because such large, unexpected and rapid changes are rare. Sea ice coverage is still well below average now.
We wanted to know what caused this unprecedented decline of Antarctic sea ice and what changes in the system have sustained those declines. We also wanted to know if this was a temporary shift or the beginning of a longer-term decline, as predicted by climate models. Finally, we wanted to know whether human-induced climate change contributed to these record lows.
Hunting for clues
Sea ice cover around Antarctica varies a lot from one year or decade to the next. In fact, Antarctic sea ice cover had reached a record high as recently as 2014.
That provided a clue. As year-to-year and decade-to-decade sea ice cover varies so much, this can mask longer-term melting of sea ice due to anthropogenic warming.
The next clue was in records broken far away from Antarctica. In the spring of 2016 sea surface temperatures and rainfall in the tropical eastern Indian Ocean were at record…
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