Spitzbergen Current - Vertical Movement

Vertical Movement

After the WSC splits off from the Norwegian Atlantic Current it begins to enter very cold atmospheric conditions. The cold atmosphere is able to cool the surface water, and in some instances this water cools so much that some of the WSC water actually sinks due to its density increase, all the while holding its salinity constant. This is one element of the formation of the Lower Arctic Intermediate Water. As the current continues to move northward and reaches the continental shelf of western Svalbard it begins to encounter sea-ice. The sea-ice melts due to the warmth of the WSC, and thus a surface layer of very freshwater begins to exist. Winds mix the freshwater and the warm salty water of the WSC mix, creating some Arctic Surface Water. This Arctic Surface Water is now less dense than the Atlantic Water in the WSC and thus the WSC begins to sink underneath the Arctic Surface Water. At this point the WSC is still relatively warm and very saline. Thus, this allows the Atlantic Water in the WSC to be completely isolated from the surface waters.

After the current splits into the Svalbard Branch and the Yermak Branch, the general sinking process described above still continues in the Svalbard Branch. However, in the Yermak Branch the WSC is not able to penetrate deep inside the Arctic Ocean because the zone it enters has very strong tidal mixing. This allows the Atlantic Water to mix with the Polar Waters, creating more of a homogeneous mixture of relatively warm and moderately saline water. This extends down to about 300 meters which is recognized as the bottom depth of the Return Atlantic Current. For the Svalbard Branch, the Atlantic Water core of the WSC continues to sink as it meets more and more freshwater on its eastern route. It sinks fairly quickly to a depth greater than 100 meters by the time it reaches the Barents Sea because in Northern Svalbard there is quite a lot of freshwater run-off from fjords which adds to a deeper, less dense Arctic Surface Water and thus a deeper WSC. By the time this water recirculates to the Beaufort Gyre, the Atlantic core of the WSC is 400 to 500 meters deep. Unlike the Yermak Branch and the Return Atlantic Current, the Svalbard Branch is able to retain a strong Atlantic Water chemical signal whereas the Yermak Branch and the Return Atlantic Current carry a very weak Atlantic Water signal. The Atlantic Water core temperature is a direct reflection of the depth of the Svalbard Branch of the WSC.

It is important to note that if the WSC encounters a significant amount of ice along the continental shelves of Spitsbergen, then the WSC advancing poleward will sink much faster, due to a greater amount of freshwater melt from the increased sea-ice. The ability to sink faster means more of the heat content of the WSC will be preserved and not lost to the atmosphere or surrounding waters and thus warmer waters will be transported into the Arctic. This could have profound impacts on sea-ice melting.