Two species of seal found in the Antarctic seas are helping scientists collect data about the temperature and salinity of waters around vulnerable ice sheets in West Antarctica.
Environmental scientists at the University of East Anglia (UEA), UK, have been investigating ways of studying warm, salty, deep water in the Amundsen Sea in the Southern Ocean. Understanding more about how this water gets towards the ice shelves by measuring its temperature, salinity and depth will help climate change modellers make more accurate predictions about how rapidly the Antarctic ice sheet is melting.
It has been estimated that the melting west Antarctica ice sheet contributes to sea level rise by up to 3.2 metres, with much of the water draining through two glaciers:
- Pine Island Glacier; and
- Thwaites Glacier.
Estimates of future sea level rise vary a lot, and scientists need year-round observations to assess and improve climate change models.
Gathering data in summer months is relatively straightforward, but getting ships near the area during the winter is impossible because the area is covered in a thick blanket of sea ice. The only information available is from ‘moorings’, strings of measurement devices anchored to the sea floor, which can collect data from a few fixed locations, but they cannot measure near the sea surface at all because the huge icebergs would collide with them.
Addressing the issues for the research into ice sheet melt
The UEA team set up a collaboration with the Sea Mammal Research Unit and the University of St Andrews, Scotland, to address this issue. The expedition built on an idea originally suggested by scientists at the British Antarctic Survey (BAS) when they became aware of a large elephant seal haulout on islands near the Pine island Glacier.
The team tagged seven southern elephant seals and seven Weddell seals with devices that can send information by satellite. Measurements of the warmth and saltiness of the water were sent by the seals as they moved around the area and dived from the surface of the ocean down through the water to the sea bed in their hunt for food.
Helen Mallett, who led the study at UEA, said: “We were able to collect much more information from the seals than all the previous ship-based surveys in the area combined and it was clear that, at least during the seasons we observed, there were substantial differences in temperature between the seasons.”
After analysing the findings, the researchers discovered that not only is the layer of circumpolar deep water thicker in winter, it is also warmer and saltier than during summer months. This suggests that there is likely to be more melting of the ice sheets during the winter months than previously thought.
Mallett added: “Although more will need to be done to measure these differences over a number of years, it’s clear that enlisting seals to collect this kind of ocean data will offer useful insights for climate change modellers who are attempting to predict how fast sea levels will rise.”