Abstract

Antarctic sea ice is an important component of the Earth system. However, its role in the Earth system is still not very clear due to limited Antarctic sea ice thickness (SIT) data. A reliable sea ice reanalysis can be useful to study Antarctic SIT and its role in the Earth system. Among various Antarctic sea ice reanalysis products, the Global Ice-Ocean Modeling and Assimilation System (GIOMAS) output is widely used in the research of Antarctic sea ice. As more Antarctic SIT observations with quality control are released, a further evaluation of Antarctic SIT from GIOMAS is conducted in this study based on in-situ and satellite observations. Generally, though only sea ice concentration is assimilated, GIOMAS can basically reproduce the observed variability of sea ice volume and its changes in the trend before and after 2013, indicating that GIOMAS is a good option to study the long-term variation of Antarctic sea ice. However, due to deficiencies in model and asymmetric changes in SIT caused by assimilation, GIOMAS underestimates Antarctic SIT especially in deformed ice regions, which has an impact on not only the mean state of SIT but also the variability. Thus, besides the further development of model, assimilating additional sea ice observations (e.g., SIT and sea ice drift) with advanced assimilation methods may be conducive to a more accurate estimation of Antarctic SIT.

Highlights

  • Antarctic sea ice plays an important role in the Earth system

  • Global Ice-Ocean Modeling and Assimilation System (GIOMAS) can reproduce the asymmetry in the annual cycle of Antarctic sea ice volume (SIV) observed by ES and CS2 while underestimates SIV by about 48.5% on average when compared to ES 135 as well as CS2

  • Above underestimation can be partially attributed to the 205 uncertainties of sea ice thickness (SIT) retrieved from satellite, SIT underestimation in the northwest Weddell Sea is further verified by the comparison between GIOMAS and upward looking sonar (ULS) observations

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Summary

Introduction

Antarctic sea ice plays an important role in the Earth system. Firstly, Antarctic sea ice can influence the Earth climate system. There are still large uncertainties of present sea ice reanalysis in the Southern Ocean (Uotila et al, 2019; Shi et al, 2021), suggesting the necessity and importance of evaluating them. Among a number of Antarctic sea ice reanalysis, the Global Ice-Ocean Modeling and Assimilation System (GIOMAS) is one of the most widely used in studies of Antarctic sea ice. For instance, GIOMAS has been regarded as the reference in the 60 assessments of simulations (Shu et al, 2015; Uotila et al, 2017; DuVivier et al, 2020) and predictions (Ordoñez et al, 2018; Morioka et al, 2021). More in-situ observations are obtained 70 from dedicated research stations, icebreakers and autonomous underwater vehicles due to increasing research activities in the Antarctic These provide an opportunity to further evaluate Antarctic SIT of GIOMAS.

Data and methods
Results
Conclusions and discussion
240 Data availability
255 Acknowledgments
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