A 4.5 km resolution Arctic Ocean simulation with the global multi-resolution model FESOM 1.4

Qiang Wang,Sergey Danilov,Xuezhu Wang,Thomas Jung,Claudia Wekerle

doi:10.5194/gmd-11-1229-2018

Abstract

Abstract. In the framework of developing a global modeling system which can facilitate modeling studies on Arctic Ocean and high- to midlatitude linkage, we evaluate the Arctic Ocean simulated by the multi-resolution Finite Element Sea ice-Ocean Model (FESOM). To explore the value of using high horizontal resolution for Arctic Ocean modeling, we use two global meshes differing in the horizontal resolution only in the Arctic Ocean (24 km vs. 4.5 km). The high resolution significantly improves the model's representation of the Arctic Ocean. The most pronounced improvement is in the Arctic intermediate layer, in terms of both Atlantic Water (AW) mean state and variability. The deepening and thickening bias of the AW layer, a common issue found in coarse-resolution simulations, is significantly alleviated by using higher resolution. The topographic steering of the AW is stronger and the seasonal and interannual temperature variability along the ocean bottom topography is enhanced in the high-resolution simulation. The high resolution also improves the ocean surface circulation, mainly through a better representation of the narrow straits in the Canadian Arctic Archipelago (CAA). The representation of CAA throughflow not only influences the release of water masses through the other gateways but also the circulation pathways inside the Arctic Ocean. However, the mean state and variability of Arctic freshwater content and the variability of freshwater transport through the Arctic gateways appear not to be very sensitive to the increase in resolution employed here. By highlighting the issues that are independent of model resolution, we address that other efforts including the improvement of parameterizations are still required.

Highlights

The Arctic Ocean is the smallest among the world oceans, but it is a very important component of the global climate system due to its geographical location
We explored the impact of high horizontal resolution on the circulation of the Atlantic Water (AW) in the intermediate layer and FW in the upper layer of the Arctic Ocean
The simulations of the unstructured-mesh ocean–sea ice model Finite Element Sea ice-Ocean Model (FESOM) (Wang et al, 2014) with two global meshes differing in resolution in the Arctic Ocean are evaluated

Summary

Introduction

The Arctic Ocean is the smallest among the world oceans, but it is a very important component of the global climate system due to its geographical location. The liquid freshwater stored in the upper Arctic Ocean results in a strong stratification and helps to form a permanent halocline. This limits the upward heat flux from the underlying warm water and allows for a persistence of sea ice cover (Rudels et al, 1996). The Arctic Ocean receives a large amount of FW from river runoff, net precipitation, and Pacific Water through the Bering Strait (Serreze et al, 2006; Dickson et al, 2007; Haine et al, 2015; Carmack et al, 2016). Wind variability over continental shelves can locally induce more significant changes in FW content than the variability from river fluxes, and the variation in large-scale atmospheric circulation (Arctic Oscillation) can modify the pathway of river runoff, changing the FW distribution between the Arctic basins (Dmitrenko et al, 2008; Morison et al, 2012)

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Discussion

Conclusion