Changing Arctic: Estimation of freshwater changes over the full Arctic basin including land and ocean from satellite observations (part of the SENSE Centre for Doctoral Training)

Rapid Arctic warming drives profound change in the marine environment. It has strong socio-economic impacts in the Arctic but also affecting Europe including climate and weather hazards and food security [1]. The Arctic Ocean (AO) is a semi-closed basin mostly covered by sea ice but with a fast-declining pace of 13% per decade [NSIDC 1979-2019 September]. Air-sea exchange of heat and momentum are increased in this opening ocean in addition to freshwater input from the Greenland ice sheet and an intensification of the global water cycle leading to a freshwater input in the AO. Freshwater content in the AO is critical for the Atlantic Meridional Overturning Circulation (AMOC) which is responsible for 25% of heat transport to polar latitude [2] and its strength has significant impact on European climate [3].

Our knowledge of the AO is very limited compared to other ocean basins due to its difficult access and depend on very sparse in situ measurements. Despite this, we know its sea surface salinity (SSS) variability to be very high, both spatially from 27 to 35 psu and seasonally with variation higher than 4 psu. The AO drainage basin is covering Greenland, most of Russia and Canada and is characterized by big river runoff driving most of the variability on Siberian and Canada continental shelf [4].

AO satellite observations are generally difficult due to mix of sea and sea ice in observations. However, specific processing of satellite observations in altimetry and SSS [5] have recently shown promising results.

In this project, you will combine satellite observations of satellite precipitation (GPM) over the full Arctic basin, with satellite observations of land soil moisture or freezing state (e.g. from SMOS), river run-off (altimetry, SWOT), land ice changes and sea surface water content from surface (SSS, sea ice) and integrated (altimetry) measurements, to produce a complete picture of freshwater changes in the Arctic freshwater system.

Research questions
What is the freshwater content over the Arctic Ocean drainage basin and its spatio-temporal variability?
What are the physical processes governing the spatio-temporal variability and as function of the different time scales (seasonal, interannual)?
How do these Arctic Ocean processes impact the Earth climate system?
Methodology
We will use satellite data that are freely available from NASA, ESA, EUMETSAT repositories and specifically the relevant ESA Climate Change Initiative Essential Climate Variable, ice sheet, permafrost, sea surface salinity, sea ice, sea level, …. NASA-CNES (+ CAS, UKSA participation) SWOT satellite mission data will be used at the end of the PhD project.

Regional numerical model outputs are freely available from the EU Copernicus Marine Environment Monitoring Service (CMEMS) and reanalysis from ECMWF (ERA5). In addition, we will also take advantage of the high-resolution coupled model developed conjointly between NOC and MetOffice

Training
In addition to the comprehensive personal and professional development training provided within the SENSE programme, you will have the opportunity to participate in a research oceanographic cruise. You will also have the opportunity to work closely with the European Space Agency with a 3-month placement in Frascati (ESA-ESRIN) close to Roma, Italy.