Map of Field Activities
Map showing location of our fieldwork sites near Scott Base during the winter of 2009. PRC is the location of our Pegaus Road Camp on the multiyear sea ice, which we have now relocated to the point marked EBC, which is our Erebus Bay Camp. FRC marks the point where we had a camera over looking the sea ice edge before the sun set and it got too dark to see. The insets show where we are in relation to the Ross Sea and the Antarctic continent.
Our Erebus Bay Camp
Photo of the three science huts comprising our Erebus Bay Camp with the lights of the Aurora Australis over head. Taken on June 29.
Recent Data and Results
July 2009
The map above shows the location of our new sea ice on the first year ice north of the Hut Point Peninsula. We have named this camp the Erebus Bay Camp (EBC). We had to wait until until the ice was thick and safe enough before we could do this. It was around 50cm thick when we first visited the area and it has grown almost a metre since that time. The first graph below shows the thickening of the sea ice near the EBC since the middle of May. We are over a month past mid-winter and the ocean underneath the ice seems to have lost all its heat and is now within a few hundredths of a degree Celcius of its surface freezing temperature of around -1.92C. The top graph below shows the the cooling that has taken place since we first arrived in February. Each line shows the average temperature over a different depth range. The upper layers cooled considerably up until around mid-April, when they approaced the surface freezing temperature and the rate of cooling decreased. In places, the water is actually below its surface freezing point, which is only possible by coming into contact with ice at depth where the increased pressure lowers the freezing point. This process leads to the creation of platelet ice which can float up to the surface from deeper in the ocean and contribute to the tickness of the ice. So far though, we have not seen much of this ice.
Ice thickness measured using hot wire gauges at four stakes at our mass balance site near the Erebus Bay Camp (EBC) (see map above)
Average temperatures over different depth ranges calculated from our full-depth profiles
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April 2009
We've been continuing our ice and ocean observations, which tell us that although the thick multiyear sea ice is still melting, the ocean has cooled significantly since we arrived. The first of the three graphs below shows how the thickness of the sea ice has been changing over time. Although there have been a few times when thought the meltmight have stopped, the ice has lost over 20 cm from the bottom in some places since March 17. The second graph shows how the temperature of the water under the ice has varied over the same time period at three different depth ranges. As we saw in our earlier profiles (data from February and March, below), the warmest water was between approximately 50-150m below the surface. However,this mid-depth layer has been cooling consistently and last week we saw for the first time that it was cooler than the surface layer. With less heat in the ocean, we expect to see the ice at out field site start to grow again very soon. And soon after that, we'll hopefully start to see the supercooled water and platelet ice that we came down here to study.
Ice thickness measured using hot wire gauges at four stakes at our field site on the multiyear sea ice in MMurdo Sound (see map above)
Average temperatures over different depth ranges calculated from our full-depth profiles
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February-March 2009
During early winter, while we are waiting for new to ice grow thick enough, we are confining our work to thicker, multiyear sea ice at the southern end of McMurdo Sound. We've not set up a camp on the ice yet, but we've set out a mooring under the ice and we've been keeping a hole open through which we've measuring the properties of the ocean. The map above shows the area we've been working in and the graphs below show profiles of the temperature and salinity from just under the ice to to just above the sea bed. At depth the ocean is close to its surface freezing temperature (about -1.9 C), but you'll see that there is a layer of warmer water sitting on top. This water is also fresher than the water below. However, during the time we've been here so far, we're starting to see this surface layer get colder and saltier - a sure sign winter is on the way.
Four mean profiles of temperature (red) and salinity (blue) under the sea ice since we've taking measurements this year.
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