Cruise summary

Now that the research voyage is nearing its end, what has been achieved by the team of 24 scientists and engineers? We’re delighted by the quantity and quality of the observations and data sets that we’ve been able to obtain. We’ve been helped by the unusually small amounts of sea ice in Pine Island Bay & this meant that we could get to areas that are very rarely accessible. There are many aspects of the data that will take many months of careful study to understand the processes fully, and other chemical measurements that we can’t even start to analyse until we get the samples transported home to our laboratories. However here are some of the highlights so far:

  • We’ve mapped the temperature, salinity, current velocity and amount of oxygen in the water, at 105 places all over the eastern Amundsen Sea from the edge of the glaciers to where the continental shelf ends and the sea bed slopes steeply down to the ocean abyss. We’ve been exploring some places where no-one has ever measured what the ocean is like. It is very exciting to be able to map the paths of a current for the first time.
  • Some of the observations were repeats of temperature and salinity measurements made by other oceanographers in 1994, 2003, 2007 or 2009. Compared with 2009, our measurements in 2014 show that the deep layer of warm salty water is thinner and so the water reaching the ice shelf is colder than in 2009.
  • 14 seals are now sporting the latest in stylish headgear. They have obligingly spread out all over the eastern Amundsen Sea. One surprise is that they seem to be targeting the fronts of the various ice shelves for their foraging. We don’t yet know why that might be!
  • We’ve sent an autonomous submarine into the cavity beneath the ice shelf, measuring the properties of the water and the currents. It ventured bravely all the way to the grounding line, where the ice meets the solid earth continent of Antarctica, well below sea level. The sub discovered some fascinating waves in the sea bed, that might be caused by the ice shelf moving up and down in previous years or centuries.
  • The water that enters into the cavity beneath Pine Island Glacier is relatively warm and salty (ok, by “warm” we mean about zero Celsius!). This warm water melts the ice shelf and the resulting meltwater is mixed in. This water eventually exits higher up than it entered, because it has now got some fresh (not salty) water mixed in. We’ve studied the area where this meltwater mixture comes out. We’re looking forward to the results of the various chemical tracer measurements in this meltwater.
  • A big surprise has been the large amount of mixing happening in the meltwater just after it comes out from under the ice shelf. We’ve measured this for the first time and are coming up with theories for what is causing this turbulence.
  • We’ve recovered 63 instruments (of which 62 worked!) that have been moored to the sea bed in 7 places for the last 2 years, measuring temperature, salinity and current velocity all the time. 2012 was a very different year from 2013 with very different temperatures.

We’re looking forward to exploring why this is. We’re now steaming back to Rothera, one of the British Antarctic bases on the Antarctic Peninsula. We should arrive on Saturday, when we’ll be transferred to a small plane to fly back to Punta Arenas, almost exactly 6 weeks since we left!

Via: Ocean2ice blog

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