Recent Sea Ice Decline Did Not Significantly Increase the Total Liquid Freshwater Content of the Arctic Ocean

Abstract

The freshwater stored in the Arctic Ocean is an important component of the global climate system. Currently the Arctic liquid freshwater content (FWC) has reached a record high since the beginning of the last century. In this study we use numerical simulations to investigate the impact of sea ice decline on the Arctic liquid FWC and its spatial distribution. The global unstructured-mesh ocean general circulation model Finite Element Sea Ice–Ocean Model (FESOM) with 4.5-km horizontal resolution in the Arctic region is applied. The simulations show that sea ice decline increases the FWC by freshening the ocean through sea ice meltwater and modifies upper ocean circulation at the same time. The two effects together significantly increase the freshwater stored in the Amerasian basin and reduce its amount in the Eurasian basin. The salinification of the upper Eurasian basin is mainly caused by the reduction in the proportion of Pacific Water and the increase in that of Atlantic Water (AW). Consequently, the sea ice decline did not significantly contribute to the observed rapid increase in the Arctic total liquid FWC. However, the changes in the Arctic freshwater spatial distribution indicate that the influence of sea ice decline on the ocean environment is remarkable. Sea ice decline increases the amount of Barents Sea branch AW in the upper Arctic Ocean, thus reducing its supply to the deeper Arctic layers. This study suggests that all the dynamical processes sensitive to sea ice decline should be taken into account when understanding and predicting Arctic changes.

Evaluation of global ocean–sea-ice model simulations based on the experimental protocols of the Ocean Model Intercomparison Project phase 2 (OMIP-2)

“…Both OMIP-1 and OMIP-2 simulations show high salinity bias in the Arctic Ocean, with some reduction implied for OMIP-2 simulations. Note that the Arctic Ocean has shown a strong freshening trend over recent decades (Rabe et al, 2014;Wang et al, 2019), thus restoring sea surface salinity to the climatology in the models may result in high salinity biases. The model spread is large in the Arctic Ocean, where the 310 diversity among models in the sea ice processes, the surface vertical mixing processes, and the treatment of salinity restoring can lead to large difference in sea surface salinity.…”

Assessment of the Finite-volumE Sea ice-Ocean Model (FESOM2.0) – Part 1: Description of selected key model elements and comparison to its predecessor version

“…1a), it has been shown that FESOM1.4 performs as well as a variety of coarse structured-mesh ocean models, in terms of modeled general ocean circulation (e.g., Danabasoglu et al, 2016;Wang et al, 2016b, c). The range of medium-sized meshes between 500 and 2000 K surface vertices includes the meshes with either globally increased resolution to a higher extent or locally strongly refined key regions of interest (Wang et al, 2016a(Wang et al, , 2018a(Wang et al, , b, 2019bWekerle et al, 2017;Sein et al, 2016Sein et al, , 2018. Using FESOM1.4, it was shown that this class of meshes is well suited for ocean-only simulations, as well as for fully coupled model simulations, which, however, require sufficiently large amounts of computational resources.…”

Assessment of the Finite VolumE Sea Ice Ocean Model (FESOM2.0), Part I: Description of selected key model elements and comparison to its predecessor version

“…1 left) it has been shown that FESOM1.4 performs as well as a variety of coarse structured mesh ocean models, in terms of modeled general ocean circulation (e.g Danabasoglu et al, 2016;Wang et al, 2016aWang et al, , 2016b. The range of medium-sized meshes between 500K until 2000K surface vertices, includes the meshes with either globally increased resolution to a higher extent or locally strongly refined key regions of interest (Wang et al, 2016(Wang et al, , 2018a(Wang et al, ,b, 2019bWekerle et al 2017;Sein et al 2016Sein et al , 2018. Using FESOM1.4 it was shown that this class of meshes are well suited for ocean only simulations, as well as for fully coupled model simulations, which, however, require sufficiently large amounts of computational resources.…”