Information
Comments
A glorious day in the Southern Ocean, with clear skies, a flat sea and the first icebergs in view. We are starting to work our way up the continental slope to Antarctica, with the depth of the stations gradually decreasing. The temperature at the bottom of the last cast was about -0.6 degrees C, at a depth of 4000 m. (Sea water freezes at a temperature of about -1.9C.) The temperature below 0 degrees indicates that we are now far enough south to reach the Antarctic Bottom Water. At a handful of places around Antarctica, including the Mertz Glacier region, the conditions are right to convert light water sitting at the sea surface into water that is sufficiently dense to sink to the sea floor, 4 or 5 km below the surface. This water sinking near the continent is called Antarctic Bottom Water. The ocean currents associated with the formation and export of bottom water are an important part of the climate system. On previous voyages to this area, we have shown that the bottom water has become less salty and less dense in recent decades, probably as the result of an inflow of glacial melt water. One of the main goals of the present voyage is to see if this trend is continuing and to test the idea that increased melting of Antarctic ice is contributing to the signal we see in the ocean.
REGARDS: Steve, Fred and Penny
Map
A map showing Australia and Antarctica. The map shows the journey of one voyage that has occured in the season, with each route highlighted in a distinct colour.