Sea surface height anomaly and geostrophic current velocity from altimetry measurements over the Arctic Ocean (2011–2020)

Abstract

Abstract. Satellite altimetry missions flying over the ice-covered Arctic Ocean have opened the possibility of further understanding changes in the ocean beneath the sea ice. This requires complex processing of satellite signals emerging from the sea surface in leads within the sea ice, with efforts to generate consistent Arctic-wide datasets of sea surface height ongoing. The aim of this paper is to provide and assess a novel gridded dataset of sea surface height anomaly and geostrophic velocity, which incorporates both the ice-covered and open ocean areas of the Arctic. Data from the CryoSat-2 mission in the period 2011–2020 were gridded at monthly intervals, up to 88∘ N, using the Data-Interpolating Variational Analysis (DIVA) method. To examine the robustness of our results, we compare our dataset to independent satellite data, mooring time series and Arctic-wide hydrographic observations. We find that our dataset is well correlated with independent satellite data at monthly timescales. Comparisons to in situ ocean observations show that our dataset provides reliable information on the variability of sea surface height and surface geostrophic currents over geographically diverse regions of the Arctic Ocean and different dynamical regimes and sea ice states. At all comparison sites we find agreement with in situ observed variability at seasonal to interannual timescales. Furthermore, we find that our geostrophic velocity fields can resolve the variability of boundary currents wider than about 50 km, a result relevant for studies of Arctic Ocean circulation. Additionally, large-scale seasonal features emerge. Sea surface height exhibits a wintertime Arctic-wide maximum, with the highest amplitude over the shelves. Also, we find a basin-wide seasonal acceleration of Arctic slope currents in winter. We suggest that this dataset can be used to study not only the large-scale sea surface height and circulation, but also the regionally confined boundary currents. The dataset is available in netCDF format from PANGAEA at https://doi.org/10.1594/PANGAEA.931869 (Doglioni et al., 2021d).

NCDatasets.jl: a Julia package for manipulating netCDF data sets

“…There are currently 64 registered Julia packages (as for 15 January 2024) that have NCDatasets as direct or indirect dependency (not counting for optional dependencies). For example, NCDatasets is used with satellite data (Barth et al, 2022;Doglioni et al, 2023), in situ observations (Belgacem et al, 2021;Shahzadi et al, 2021) as well as numerical ocean models (Ramadhan et al, 2020) and atmospheric models (Klöwer et al, 2023).…”

Arctic Ocean simulations in the CMIP6 Ocean Model Intercomparison Project (OMIP)

“…Changes in sea surface height in the Arctic Basin reflect the variation of liquid freshwater content (e.g., Morison et al, 2012;Wang et al, 2021). Furthermore, inter-annual changes in sea surface height are good indicators of inter-annual changes in the upper Arctic Ocean circulation (Morison et al, 2021), because surface geostrophic currents dominate the Arctic surface velocity on spatial scales larger than 10 km and timescales longer than a few days (Doglioni et al, 2023). To evaluate the mean state and variability of upper-ocean circulation, we compare modeled sea surface height with observational estimates from altimetry measurements provided by Armitage et al (2016).…”

“…The changes of the Arctic Ocean potentially affect the climate system beyond the Arctic. For example, the sea-ice decline in the Arctic tends to cause cold winters and extreme weather events over the mid-latitude continents in the Northern Hemisphere Outten and Esau, 2012;Kim et al, 2014;Cohen et al, 2020), and the storage and release of freshwater from the Arctic Ocean can influence the large-scale ocean circulation by freshening the upper North Atlantic ocean (Jungclaus et al, 2005;Goosse et al, 1997;Wadley and Bigg, 2002;Shu et al, 2017;Zhang et al, 2021).…”