Arctic Sea Level Budget Assessment during the GRACE/Argo Time Period

Roshin Raj,Jérôme Benveniste,Laurent Bertino,Per Knudsen,Stine Rose,Ole Andersen,Anny Cazenave,Antonio Bonaduce,J Ø Nilsen,Benjamin Gutknecht,Martin Horwath,Heidi Ranndal,Carsten Ludwigsen,Anna Hogg,Sourav Chatterjee,Hindumathi Palanisamy,Kristin Richter,Johnny Johannessen

doi:10.3390/rs12172837

Abstract

Sea level change is an important indicator of climate change. Our study focuses on the sea level budget assessment of the Arctic Ocean using: (1) the newly reprocessed satellite altimeter data with major changes in the processing techniques; (2) ocean mass change data derived from GRACE satellite gravimetry; (3) and steric height estimated from gridded hydrographic data for the GRACE/Argo time period (2003–2016). The Beaufort Gyre (BG) and the Nordic Seas (NS) regions exhibit the largest positive trend in sea level during the study period. Halosteric sea level change is found to dominate the area averaged sea level trend of BG, while the trend in NS is found to be influenced by halosteric and ocean mass change effects. Temporal variability of sea level in these two regions reveals a significant shift in the trend pattern centered around 2009–2011. Analysis suggests that this shift can be explained by a change in large-scale atmospheric circulation patterns over the Arctic. The sea level budget assessment of the Arctic found a residual trend of more than 1.0 mm/yr. This nonclosure of the sea level budget is further attributed to the limitations of the three above mentioned datasets in the Arctic region.

Highlights

Studies of Arctic Sea level budget are necessary and challenging since the Arctic sea level determination is affected by many factors, such as seasonal to permanent sea-ice cover, incomplete regional coverage of satellites and in situ temperature and salinity measurements, the ability of the satellite instrument to measure sea ice freeboard height, insufficient geophysical models, residual orbit errors, and challenging retracking of satellite altimeter data [20]
We present the results of the Arctic sea level budget assessment estimated using the latest release of the datasets with the focus on the combined Gravity Recovery and Climate Experiment (GRACE)/Argo period from 2003–2016
While ERS-1, ERS-2 and Envisat are conventional altimetry or low-resolution mode (LRM) data sets processed with a single processor, CryoSat-2 consists of three types: LRM; Synthetic Aperture Radar (SAR); and SAR Interferometry (SARIn), which are processed with different processors [20]

Summary

Introduction

Studies of Arctic Sea level budget are necessary and challenging since the Arctic sea level determination is affected by many factors, such as seasonal to permanent sea-ice cover, incomplete regional coverage of satellites and in situ temperature and salinity measurements, the ability of the satellite instrument to measure sea ice freeboard height, insufficient geophysical models, residual orbit errors, and challenging retracking of satellite altimeter data [20]. Note that the sea level data produced is the first Arctic sea level anomaly (SLA) record including a physical retracker of raw altimeter waveforms (ALES+) [21], dedicated to retrieving the specular returns from leads in the sea-ice cover This improves the stability of the SLA near the ice edge essentially due to the possibility of adding the sea state bias correction computed from ALES+. Results are presented and discussed, which starts with the analysis of the altimeter data (Section 3.1), followed with the analysis of ocean mass change (Section 3.2) and steric height data (Section 3.3). This is followed by the assessment of the sea level budget of the Arctic (Section 3.4).

Methods

Results

Conclusion