Determining Arctic Sea Level Change with Geodesy and In-Situ data
Abstract
As one of the most remote and inaccessible regions in the world, sea level in the Arctic is still today in large parts uncertain. Altimetric measurements by satellites have been available in the Arctic for more than 25 years. However, when converting the radar pulse signal to sea surface heights (retracking), different methods exist to treat areas 'contaminated' by sea-ice and the merging of Low-Resolution Mode (LRM) data with SAR data. Furthermore, until the launch of CryoSat-2, satellite altimetry only covered up to 81.5N leaving a 'pole hole' with unknown sea levels.
Another way of finding the 'true' sea level in areas without tide gauges is by using Ocean Bottom Pressure (OBP) derived from GRACE which is unaffected by sea ice and adding the steric sea level change, derived from either models or in-situ temperature and salinity depth profiles. However mass leakage from land ice makes it necessary to apply large corrections to divide land and ocean gravity signals from GRACE, and T/S-profiles are only sparse due to harsh environment in the Arctic. 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, thereby making the contributions to the sea level budget (SSH=mass+steric) independent of each other. 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 (Ludwigsen and Andersen (in review)).- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.G53C0633L
- Keywords:
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- 1218 Mass balance;
- GEODESY AND GRAVITY;
- 1223 Ocean/Earth/atmosphere/hydrosphere/cryosphere interactions;
- GEODESY AND GRAVITY;
- 1225 Global change from geodesy;
- GEODESY AND GRAVITY;
- 1655 Water cycles;
- GLOBAL CHANGE