Interannual variability of the Arctic freshwater cycle in the second half of the twentieth century in a regionally coupled climate model

Anne Laura Niederdrenk,Dmitry V Sein,Uwe Mikolajewicz

doi:10.1007/s00382-016-3047-1

Anne Laura Niederdrenk, Dmitry V Sein + Show 1 more

Open Access

https://doi.org/10.1007/s00382-016-3047-1

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Journal: Climate dynamics	Publication Date: Mar 12, 2016
Citations: 10	License type: CC BY 4.0

Affiliation: Max Planck Institute for Meteorology

Abstract

We use a regionally coupled ocean-sea ice-atmosphere-hydrological discharge model to investigate the influence of changes in the atmospheric large-scale circulation on the interannual variability of the Arctic freshwater (FW) components. This model includes all sinks and sources of FW and allows for the analysis of a closed FW cycle in the Arctic. We show that few atmospheric winter modes explain large parts of the interannual variability of the Arctic FW cycle. A strong Icelandic low causing anomalous strong westerlies over the North Atlantic leads to warmer and wetter conditions over Eurasia. The ocean circulation is then characterized by a strong transpolar drift leading to increased export of FW in liquid and solid form into the North Atlantic. In contrast to this, a weaker than usual Icelandic low and a strong Siberian high is associated with a strong Beaufort Gyre and thus an accumulation of FW within the Arctic Ocean. Not only specific winter conditions but also increased precipitation in late spring and summer, caused by enhanced cyclone activity over land, lead to increased Eurasian runoff, which is responsible for most of the variability in Arctic river runoff.

Highlights

Observations and model results indicate that the Arctic climate and its FW components change rapidly within the last decades (Meehl et al 2007)
While other model studies disagree on the mean value as well as on the variability of the FW components, our results are in good agreement with observations
The Arctic FW components are improved compared to the global model MPIOM / ECHAM 5, especially in the regions where high resolution leads to a better representation of the complex topography

Summary

Introduction

Observations and model results indicate that the Arctic climate and its FW components change rapidly within the last decades (Meehl et al 2007). Coupled regional models used for Arctic climate investigations (Döscher and Koenigk 2013; Koenigk et al 2010; Mikolajewicz et al 2005) have two disadvantages compared to global coupled models: Firstly, they generally only cover the Arctic Ocean and not the adjacent catchment areas of the rivers draining into the Arctic and prescribe the runoff of the Arctic rivers They use salinity restoring or flux correction, and thereby disturb the FW budget artificially.

Model setup and experimental design

Comparison with observations and the global model

Internal model variability

Modes of atmospheric variability

Variability of Arctic river runoff

Summary and conclusion