Where are we going and why is it so important ? The ice in Antarctica rests on solid bedrock – contrary to the ice on the North Pole that floats on ocean water. This means that if any of Antarctica’s ice melts, it is discharged into the Southern Ocean and contributes directly to global sea-level rise. But if it is so cold in Antarctica, how can the ice melt ?
By far the largest portion of melting in Antarctica happens below the surface. Where relatively warm ocean waters access the continental shelf, they start eroding the ice from underneath and eat away ice in areas that matter the most for the stability of the grounded ice. Ok, where are these warm ocean waters then ?
You must know that water is a fascinating material. It’s highest density is at 4 degrees Centigrade. This is why frozen ice bergs float and warmer ocean waters are deep at the bottom of the sea – flowing around Antarctica far away from the ice and along the continental shelf that acts like a protective barrier. It is therefore called Circumpolar Deep Water. This warm water at the bottom of the sea can’t just simply jump onto the much shallower continental shelf. But what if there is a deep cut in the continental shelf and the warm water can pass the barrier ?
This is exactly the case in the Amundsen Sea, where we are going. Deep canyons in the continental shelf link the deeper ocean to Antarctica’s precious ice. The irony is that these deep canyons originate from past ice ages, when growing glaciers carved them out of the continental shelf as they advanced. These glaciers, however, are long gone and all they have left behind is scars in the continental shelf. This is why the icebreaker and research vessel Nathanial B. Palmer went to the Amundsen Sea last year to map the sea floor and pinpoint these canyons (here is more info about the cruise).
Where Circumpolar Deep Water gets in contact with Antarctica’s ice, it rapidly erodes floating glaciers and ice shelves from underneath. As the ice thins, it loses its stabilizing effect on the ice further uphill which causes it to speed up and discharge even more ice to the ocean. This process occurs at the Thwaites Glacier and the Dotson Ice Shelf, but the questions of how the warm waters propagate in their embayments as well as the role of areas of extremely high melt rates haven’t been answered yet. This is why we need to go there, camp on the ice and have a closer look with our scientific instruments.