Retreating glaciers in West Antarctica may cause a sea change

In a very interesting twist to the theories about the climate change saga, it has been found that the enormous glaciers of West Antarctica appear to be retreating in an ‘unstoppable’ way. The process, if it continues, could ultimately turn the West Antarctic ice sheet into an area of wide open ocean and raise global sea levels by 10ft.Though it has long been assumed that this destabilisation of West Antarctica was caused by human-induced climate change, a new study published in the journal Nature last week may have just made that story considerably more complicated, The Washington Post reported.The new research, led by researchers with the British Antarctic Survey but with accompaniment from scientists at US, German, Dutch, Swiss, and British universities, focuses on Pine Island Glacier, one of the largest and most threatening in West Antarctica. It is dumping nearly 50bn tonnes of ice into the oceans each year – more than any other glacier on the globe except for its next door neighbour, Thwaites – and could ultimately raise ocean levels by close to 2ft all on its own.This is happening because the glacier has been retreating backwards and downhill – the marine-based glacier rests in very deep waters, and the terrain behind where it currently touches the ocean gets even deeper inland. It is an unstable configuration, and scientists have long suspected that warm ocean waters created the problem by effectively un-grounding the glacier from a roughly 800m deep undersea ridge, upon which it was resting in a more stable alignment.The surprise from the new study, though, is the suggestion that the un-grounding may have started all the way back in the early to mid-1940s – while there were no satellite images of Antarctica. The early 1940s were hot for a very particular reason – a strong and long-lasting Pacific El Nino event spanning from 1939 to 1942. This mega-El Nino, a precursor to the massive El Ninos since seen in 1997-1998 and 2015-2016, affected the circulation of the atmosphere all the way down in Antarctica, where stronger winds in the Amundsen sea region can allow warmer deep waters, called “circumpolar deep water,” to move in towards the glaciers. There is general agreement that these waters are responsible for West Antarctic retreat.Through the new study researchers conclude that a little after the El Nino of 1939 to 1942, an “ocean cavity” opened up behind the ridge, one that warm waters could get into – a first sign of destabilisation. However, the ice did not lift fully off the ridge until around 1970, the researchers believe.The unavoidable question is what this sequence of events says about our own responsibility for destabilising Pine Island (and, perhaps, other West Antarctic glaciers). The world was less warm in the 1940s, after all, and the role of human-caused global warming on El Nino events remains debated.According to James Smith, a glaciologist with the British Antarctic Survey and the first author of the study, the 1940s is potentially a few years before the really big spike in anthropogenic-forced warming but it is certainly within the realms of human-induced change. Arguments are sure to flow back and forth. But one thing is clear – we are changing the planet in myriad ways with our greenhouse gas emissions.