Freshwater influence on the hydrography and dissolved CO2 of the Northeast

Abstract

The Northeast Greenland shelf and the associated fjords are an extremely dynamic Arctic environment. It is influenced by Arctic Ocean processes, the Greenland Ice Sheet, and the North Atlantic. In turn, any modifications that occur in the region are exported south, back into the North Atlantic. This thesis addresses some of the open questions in the region regarding regional water mass distribution, carbon dynamics, and fjord processes. The first research chapter presents an updated hydrography for the Northeast Greenland shelf, including observations from latitudes that were not included in previous work. We look at the sources for the water masses identified and find a clear link between the Polar Surface Water found on the Northeast Greenland shelf and the Laptev Sea region in the Siberian Arctic using geochemical tracers. The second research chapter is an investigation of the effect of the hydrographical configuration identified in the previous chapter on the carbon system. We determine that the region can act as a source of CO2 to the atmosphere rather than a sink, challenging the prior understanding of the Northeast Greenland shelf as a strong atmospheric CO2 sink. The third and last research chapter focuses on a mooring and novel automated stable water isotope sampler deployed, with a weather station, in a fjord linked to the Northeast Greenland shelf. After the maximum discharge occurs in autumn, driven by a change from along-shelf winds to piteraq, the salinity increases steadily. Nonetheless, the fjord remains stratified throughout winter between depths of 11 m and 50 m, even recovering after two high salinity events. This very stably stratified water column will be exported onto the shelf, where it will add to an already highly stratified surface water identified in the first research chapter.