Antarctica: Heat comes from the deep

A press release from the Helmholtz Centre for Ocean Research-Kiel: The water temperatures on the West Antarctic shelf are rising. The reason for this is predominantly warm water from greater depths, which as a result of global change now increasingly reaches the shallow shelf. There it has the potential to accelerate the glacier melt from below and trigger the sliding of big glaciers. These data are published today by scientists of the GEOMAR Helmholtz Centre for Ocean Research Kiel together with colleagues from the UK, the US and Japan in the international journal Science.

... "There are many large glaciers in the area. The elevated temperatures have accelerated the melting and sliding of these glaciers in recent decades and there are no indications that this trend is changing,"says the lead author of the study, Dr. Sunke Schmidtko from GEOMAR Helmholtz Centre for Ocean Research Kiel.

For their study, he and his colleagues of the University of East Anglia, the California Institute of Technology and the University of Hokkaido (Japan) evaluated all oceanographic data from the waters around Antarctica from 1960 to 2014 that were available in public databases. These data show that five decades ago, the water masses in the West Antarctic shelf seas were already warmer than in other parts of Antarctica, for example, in the Weddell Sea. However, the temperature difference is not constant. Since 1960, the temperatures in the West Antarctic Amundsen Sea and the Bellingshausen Sea have been rising. "Based on the data we were able to see that this shelf process is induced from the open ocean," says Dr. Schmidtko.

..."These are the regions in which accelerated glacial melting has been observed for some time. We show that oceanographic changes over the past 50 years have probably caused this melting. If the water continues to warm, the increased penetration of warmer water masses onto the shelf will likely further accelerate this process, with an impact on the rate of global sea level rise " explains Professor Karen Heywood from the University of East Anglia.

The scientists also draw attention to the rising up of warm water masses in the southwestern Weddell Sea. Here very cold temperatures (less than minus 1.5°C or 29°F) prevail on the shelf and a large-scale melting of shelf ice has not been observed yet. If the shoaling of warm water masses continues, it is expected that there will be major environmental changes with dramatic consequences for the Filchner or Ronne Ice Shelf, too. For the first time glaciers outside the West Antarctic could experience enhanced melting from below....

A NASA/Cryosat image of ice on the Weddell Sea