Calving glaciers in Kongsfjorden – important foraging areas for fishes, seabirds and seals
Climate change has resulted in warmer water in Svalbard and in the Arctic. The sea ice has become thinner with less extent and often occur far to the north and east of Svalbard. The glaciers in Svalbard have also shrunk and retreated, often by several hundred metres annually. Where the glaciers previously were calving iceberg into the sea, they are now firmly grounded on land. These changes affect the food availability for fishes, seabird and seals, which to a large extent use either the marginal ice zone north of Svalbard or areas close to glacier fronts to find prey. When the ice edge is far north, they will rather try their luck in finding food outside the glacial fronts.
In the inner part of Kongsfjorden (79 degrees north) in Svalbard there are still tidewater glaciers with glacial fronts in the fjord. Pressure from masses of ice from the glaciers causes large bits to fall off at the front and become icebergs floating around in the inner fjord basin. Water that runs below the glacier comes up as brown glacial water at the front of the glacier. Here, there is often great activity of foraging seabirds, especially black-legged kittiwake, northern fulmar and Arctic terns, which fly along the glacial front hunting for zooplankton and fishes near the surface.
The mechanism that concentrates prey in this area is glacial water that exits the glacier from its underside. This fresh water comes bubbling up right outside the glacial front and spreads out as a brown plume at the surface. Water from the deeper part of Kongsfjorden joins this “elevator” to the surface and zooplankton and fishes are brought along. In the confusion that occurs with osmotic shock from freshwater, they are brought up into the brown surface water without seeing anything before they are being attacked by hordes of seabird. These food sources are especially important for nesting seabird when the parents continuously need to provide food for hungry chicks in the nest.
The Norwegian Polar Institute has a project (TW-ICE) with ongoing cruise with RV Lance to the glacial fronts in Kongsfjorden. During this cruise, samples are taken of the water masses, zooplankton and benthic animals just outside the glacial front from helicopter and boat. We will determine the special characteristics of the glacial water that appears from the underside of the glacier and which animals become concentrated in front of the glaciers and are fed upon by seabird and seals. The project is part of the Centre for ice, climate and ecosystems (ICE), which is led by Dr. Harald Steen.
At the glacial front in Kongsfjorden, 28 July, 2017. Cruise Leader Haakon Hop, Norwegian Polar Institute