Drifting Apart: An iceberg the size of Delhi broke away from the Amery Ice Shelf in East Antarctica as warming air and water chip away at the frozen continent| Photo: US News

The warm up to a chilling reality

It isn’t often that Antarctica records temperatures comparable with those seen in the tropics. Yet, this fortnight, that’s exactly what happened — twice, and in quick succession. First, researchers at an Argentinian station in the Antarctic Peninsula, which juts out of north-western Antarctica towards the southern tip of South America, observed a temperature of 18.3°C on February 6. Three days later, Brazilian scientists reported a temperature of 20.75°C from an island off the peninsula. The recent observations displace previous record highs of 17.5°C and 19.8°C set in 2015 and 1982 for the mainland and entire Antarctic region respectively.

The unusually balmy temperatures in the ice-covered continent have been attributed to a mix of local and regional meteorological factors facilitated by oceanic and atmospheric circulations. The root of the warm temperatures can be traced back to a zone of warm high pressure air that moved from the southern tip of South America towards Antarctica in the beginning of February. According to meteorologists studying the event, the weakened state of the Southern Hemisphere Westerlies — winds which usually form a protective band around Antarctica, along with warm “foehn winds”, which flow along the mountain range that forms the spine of the Antarctic Peninsula — have culminated in the record-breaking temperatures in the region.

These yet-to-be-confirmed individual observations by no means paint a uniform picture of the climatic state of the entire continent. They are, however, consistent with the larger pattern of warming that has been observed over the continent, especially as observations have improved in recent years. According to the World Meteorological Organization, average temperatures have risen by about 3°C over the past 50 years with an acceleration in warming observed in the past 30 years. During the same period, ice loss from the continent has increased more than six-fold to reach an average rate of 155 ± 19 Gt per year in the decade between 2006 and 2015.

Conventional beliefs that the Arctic is more prone to the effects of global warming and human activities such as oil-drilling and that Antarctica is relatively insulated from the effects owing to its much larger mass of ice and the protected status it enjoys have all but dissipated in recent years as improved observations and simulations have trickled in. While Antarctica is still off limits for military and industrial use, markers of global warming are now well and truly visible on the continent — especially in the western regions from where accelerated glacial flows and ice loss have increasingly been reported over recent decades.

In addition to increasing atmospheric temperatures and extreme events melting ice from above, improved observational capabilities have revealed a more dangerous and subliminal mode of melting. Over the past few years, it has become clearer that incursions of warmer water from the Southern Ocean have been melting the undersides of ice shelves where they meet the Antarctic land mass and weakening the structures that effectively keep glacial flows on the continent in check. While the process has been most visible in vulnerable glaciers in Western Antarctica, evidence has increasingly pointed to the process being active in the eastern parts as well. The Southern Ocean, which has absorbed more than half the heat trapped by greenhouse gases between 2005 and 2017, is slated to get warmer. Worryingly, the prospect of meltwater from Antarctica enabling a positive feedback loop upon mixing with the ocean and causing further accelerations in melting is a highly likely scenario.

Although Antarctica alone contains enough ice to raise global sea levels by a staggering 60m, projections included in the Special Report on the Ocean and Cryosphere in a Changing Climate published by the Inter-governmental Panel on Climate Change in October 2019 indicate average global sea level rise to be between 0.43m and 0.84m by the end of the century. While the spectre of sea level rise is increasingly being viewed as a concern across coastal regions, how exactly the variability in Antarctic ice cover and the water profile of the Southern Ocean is likely to translate to atmospheric and oceanic currents is still largely unexplored territory with potentially significant impacts.

A study published last year showed that warming had contributed to a change in the direction of wind over West Antarctica, which was bringing in greater quantities of warmer ocean water and accelerating ice loss on the continent. In fact, the recent unusual warmth seen in the Antarctic Peninsula offers a snapshot of the kind of impact sustained ice loss and meltwater mixing is likely to have, especially in the southern hemisphere where several circulations are regulated by pressure differences with Antarctica. According to researchers, warmer waters around the peninsula over recent months facilitated a northward displacement of the Southern Hemisphere Westerlies, which would have normally insulated the peninsula from the incursion of warm winds from South America. Far-reaching climatic implications of Arctic warming and polar sea ice losses have just begun to be uncovered and it would be no surprise if the changes in Antarctica manifest in similar influences of global patterns.

As GHG emissions continue at a staggering pace of over 50 billion tonnes per year, the world is expected to breach 1.5°Celsius warming by mid-century if drastic cut-backs in emissions are not achieved. While governments chart their responses to extreme weather events and slow-onset events such as sea level rise and coastal incursions of sea water, drastic changes in the composition of the polar regions and their immediate surroundings could trigger variabilities in global climate through far-reaching implications on oceanic and atmospheric circulations that end up throwing a spanner in the works of any adaptive action planned by governments.