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Paper title Steric sea level in the Arctic for closing the Arctic Sea Level Budget
Authors
  1. Carsten Bjerre Ludwigsen Technical University of Denmark Speaker
  2. Ole Baltazar Andersen DTU Space
  3. Mads Ehrhorn DTU Space
  4. Stine Kildegaard Rose DTU Space
Form of presentation Poster
Topics
  • A8. Ocean
    • A8.07 Oceanographic Change of the Arctic Ocean From Space
Abstract text The Arctic Ocean is the ocean most vulnerable to climate change. Accelerating air and ocean temperatures and deglaciation of land and sea ice alters the physical dynamics of the Arctic Ocean that impacts the sea level. Hence is sea level a bulk measure of ongoing climate related processes.

A unique feature of the Arctic Ocean is that freshwater change is the most significant contribution to sea level change. Freshwater coming from land, sea ice and rivers expands the water column and changes the dynamics of ocean currents going in and out of the Arctic Ocean. For sea level analysis of the Arctic Ocean, is the steric sea level change (change of ocean water density from temperature and salinity changes) often either inverted from satellite observations (sea surface height (SSH) from altimetry minus ocean bottom pressure (OBP) from GRACE) or based on oceanographic models that are constrained with a mix of in-situ observations, altimetry and GRACE.

Recently, studies (1,2) have shown that a satellite-independent steric sea level estimate has shown to better reconstruct the sea level features observed from altimetry compared to oceanographic models. The steric estimate (DTU Steric 2020) is composed from more than 300,000 Arctic in-situ profiles, which are interpolated into a monthly 50x50 km grid from 1990 to 2015. A further advantage is the independence of altimetry (and GRACE) and therefore ideal to be used for sea level budget analysis. Some regions with sparse in-situ observations (in particular the East Siberian Seas), showed less correlation with altimetry, but is also a region with poor tide-gauge/altimetry agreement (3,4), making it difficult to validate either of the datasets.

Here we present an update of the steric sea level product presented in (1). It now includes temperature and salinity profiles up to end 2020, representing a 31-year period from 1990-2020. Additionally, the profile data is assimilated with satellite surface salinity data from SMOS and satellite sea surface temperature data from GHRSST (Group for High-Resolution Sea Surface Temperature). Furthermore, the Arctic Ocean is divided into nine significant regions, giving a better overview of significant features and statistics of the Arctic steric sea level change. The extended timeseries allows to investigate long-term climate trends of the Arctic Ocean, which can be validated against an equal long record of altimetric sea level observations (1991-2010 up to 82N, 2011-2020 up to 88N). The dataset is useful for wide range of users looking at changes in heat content, freshwater changes, validating sea level observations (from tide gauges and altimetry) and ocean bottom pressure from GRACE/GRACE-FO (i.e. constrain leakage corrections).


1) Ludwigsen, C. A., & Andersen, O. B. (2021). Contributions to Arctic sea level from 2003 to 2015. Advances in space research, 68(2), 703-710. https://doi.org/10.1016/j.asr.2019.12.027
2) Ludwigsen, C. B., Andersen, O. B., & Kildegaard Rose, S (2021). Components of 21 years (1995-2015) of Absolute Sea Level Trends in the Arctic. Ocean Science (pre-print)
3) Armitage, T. W. K., Bacon, S., Ridout, A. L., Thomas, S. F., Aksenov, Y., & Wingham, D. J. (2016). Arctic sea surface height variability and change from satellite radar altimetry and GRACE, 2003-2014.
4) Kildegaard Rose, S., Andersen, O. B., Passaro, M., Ludwigsen, C. A., & Schwatke, C. (2019). Arctic Ocean Sea Level Record from the Complete Radar Altimetry Era: 1991-2018. Remote Sensing, 11(14), 1672. https://doi.org/10.3390/rs11141672