Tracing the Imprint of River Runoff Variability on Arctic Water Mass Transformation

Erwin Lambert*, Aleksi Nummelin, Per Pemberton, Mehmet Ilıcak

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

15 Citations (Scopus)

Abstract

The Arctic Ocean receives a net freshwater input from land and from the atmosphere. This flux of freshwater, along with net surface heat loss, acts to transform the water mass properties of inflowing Atlantic and Pacific waters. In this study, model simulations are used to quantify the Arctic water mass transformation in salinity and temperature space, and its explained variance due to variability in the largest freshwater source to the Arctic: river runoff. This explained variance is quantified using a novel tool, the seasonal climate response function, which describes the magnitude and time scale of adjustment to a runoff perturbation at monthly resolution. Using this method, the transient response of Arctic water mass transformation is reconstructed over time scales ranging from several months to a decade. Model simulations with variable runoff indicate a significant explained model variance of several terms contributing to salinity transformation, including diffusion, the formation and melt of sea ice, and a possibly model-dependent surface salinity-restoring term. Most notably, an increase in river runoff strengthens the diffusion of salt and heat, which ultimately leads to an increase in the advective salt and heat import into the Arctic. These results provide evidence for the potential predictability of the Arctic system based on variability in river runoff.

Original languageEnglish
Pages (from-to)302-319
Number of pages18
JournalJournal of Geophysical Research: Oceans
Volume124
Issue number1
DOIs
Publication statusPublished - Jan 2019

Bibliographical note

Publisher Copyright:
©2018. The Authors.

Funding

We thank I. Bethke and M. Bentsen for help with implementing online diagnostics into MICOM. E. L. and M. I. are funded by the Norwegian Research Council project NORTH; P. P. is funded by NordForsk project Nordic Center of Excellence Arctic Climate Prediction: Pathways to Resilient, Sustainable Societies (ARCPATH) (Grant 76654). M. I. is also partially funded by ITU-TGA-2017-40657 and ITU Polar Research Center (PolRec). As part of the work, P. P. received a Bjerknes visiting fellowship from the Bjerknes Centre. Processed data used for the figures and computations are available at https://doi.org/10.5281/ zenodo.1886889. The idea to use CRFs arose at the 2016 FAMOS workshop during a meeting of the CRF-working group led by J. Marshall. We are grateful for detailed comments by M. Muilwijk and T. Eldevik that helped shape paper. Finally, we thank S. Groeskamp, three anonymous reviewers, and the Editor for very useful comments that greatly improved the paper.

FundersFunder number
ITU Polar Research Center
NordForsk76654, ITU-TGA-2017-40657
Norges Forskningsråd

    Keywords

    • Arctic Ocean
    • climate response function
    • river runoff
    • water mass transformation

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