Validating Arctic Sea Level Change in the GRACE-era

Carsten Ludwigsen (DTU, Denmark)

Event: 2019 Ocean Surface Topography Science Team Meeting

Session: Science I: Climate data records for understanding the causes of global and regional sea level variability and change

Presentation type: Type Oral

As one of the most remote and inaccessible regions in the world, the sea level in the Arctic is still today in large parts uncertain. Altimetry measurements by satellites have been available in the Arctic for more than 25 years. However, retrackers vary in how they treat sea surface height data contaminated by sea-ice and the merging of Low-Resolution Mode (LRM) data with SAR data and until the launch of CryoSat-2 in 2011, altimetric satellites only covered up to 81.5N.

OBP measurements from GRACE can be used to indicate the ‘truth’, but mass leakage from land ice makes it necessary to apply large corrections to divide land and ocean gravity signals from GRACE. Furthermore have recent studies (Morison et al 2012, Peralta-Ferriz et al 2014 & 2016 and Armitage 2016 & 2018) shown that especially the halosteric sea level is a larger contribution to both temporal and spatial arctic sea level variations than the actual ocean mass change seen by GRACE.

At DTU, we have collected all available hydrographic data north of the 60th latitude by adding recent data from 2016-2017 to the UDASH-database (Behrendt et al, 2017). All in-situ profiles are quality checked and finally extrapolated into a 4D-hydrographic grid covering the Arctic region for the altimetry era.

The hydrographic dataset (DTUSteric) is compared with different available datasets from GRACE and altimetry, exploiting the budget equation SSH = Mass + Steric. The best agreement (R=0.76) is reached between the combination of DTUSteric and the JPL Mascon (RL06) solution and the altimetry product from Centre of Polar Observation and Modelling (CPOM). A large residual signal is found in the East Siberian Sea, an area with no in-situ observations and in general uncertain satellite observations. The spatial correlation coefficients range from 0.32-0.76 indicating that satellite observations should be used carefully in the Arctic, as large parts of the observed sea level trend from satellite altimetry cannot be validated with in-situ data.
 

Oral presentation show times:

Room Start Date End Date
The Forum Mon, Oct 21 2019,17:15 Mon, Oct 21 2019,17:30
Carsten Ludwigsen
DTU
Denmark
caanlu@space.dtu.dk