Analysis of long term variations of ocean mass in the arctic region using satellite gravimetry

Abstract

The Arctic region has experienced rapid sea ice melt in the past decade, which leads to the global sea level rise. The volume of the ice, area and extent have been declining in recent years. The inflow of the Atlantic Ocean water into Arctic Ocean have made changes including the weaker stratification. Moreover, shoaling of Atlantic water in Eurasian Basin reduced sea ice and accelerate the Atlantic water layers’ heat fluxes further Northeast into Eurasian Basin. The salty water (denser than fresh water), the melting of sea ice and warming of Arctic Ocean surface are causing the density of water to change as well as the variations in ocean mass. These huge amounts of the mass variations lead the variations of the Earth gravity field that are being monitored by satellite gravimetry. The main objective of this thesis is to estimate and analyse ocean mass variations in the Arctic Ocean and all seas around namely Laptev Sea, Kara Sea, Barents Sea, Green Land Sea, Baffin Bay, Hudson Bay, Baffin Bay, Beaufort Sea, Chukchi Sea and East Siberian Sea. For this purpose, the standard GRACE level-2 data product from GeoForschungsZentrum (GFZ), Potsdam and the Centre for Space Research (CSR) from University of Texas has been used to estimate the ocean masses. Moreover, the Sea Level Anomaly (SLA) data from satellite altimetry was used for further analysis of the trend in the Arctic region computed from GRACE data. The SLA data is provided by Technical University of Denmark (DTU). Results show that the Beaufort Sea has experienced the highest positive trend in ocean mass of 9.99 mm/year and SLA of approximately 10 mm/year. The positive trends are influenced by the presence of Beaufort Gyre which the anticyclone winds accumulate the fresh water and deeper in this region there are cold and salty water from Pacific Ocean. The Chukchi Sea has positive trend in ocean mass of 7.64 mm/year and Sea Level Anomaly trend range from −1 mm/year and 1 mm/year. The positive trends are influenced by Pacific Ocean water which are warmer and saltier. The Baffin Bay has the strongest negative trend in ocean mass of −59.59 mm/year and Sea Level anomaly trend of approximately −9 mm/year. These negative trends are caused by the Gravitation attraction of Greenland masses and the Arctic Ocean freshwater outflows through it on the way to North Atlantic Ocean. The Hudson Bay have positive trend in ocean mass of 0.35 mm/year and Sea Level Anomaly trend ranges from 1 to 3 mm/year. The positive trends are due to large input of fresh water from river and precipitation, ice melting influenced by air temperature and inflow of Arctic Ocean waters. The Greenland Sea has negative trend in ocean mass of −9.10 mm/year and Sea Level Anomaly trend ranges between −1 mm/year and 6 mm/year. The negative trend is influenced by Gravitational attraction of Greenland masses or due to freshwater outflow from the Arctic Ocean through western side of Fram Strait. Barents Sea has positive trend in ocean mass of 0.13 mm/year and Sea Level Anomaly trend ranging from −1 mm/year to 7 mm/year. Kara Sea has positive trend in ocean mass of 3.73 mm/year, Laptev Sea has positive trend in ocean mass of 6.83 mm/year, East Siberian Sea has a positive trend of 8.25 mm/year and Arctic Ocean has positive ocean mass trend of 5.83 mm/year. The positive trends in this region are influenced by the so-called Atlantification of Arctic Ocean. The Kara Sea, Laptev Sea and East Siberian Sea all have negative trends in Sea Level Anomaly ranging from −2 mm/year to −6 mm/year. The negative trends are influenced by the gain of fresh water, net precipitation, run off increased and more discharge from the land to the sea water.