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Geoscientific Model Development An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/gmd-2018-10
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Development and technical paper
29 Mar 2018
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Geoscientific Model Development (GMD).
Dynamic hydrological discharge modelling for coupled climate model simulations of the last glacial cycle
Thomas Riddick1, Victor Brovkin1, Stefan Hagemann1,a, and Uwe Mikolajewicz1 1Max Planck Institute for Meteorology, Bundesstraße 53, 20146 Hamburg, Germany
anow at: Institute of Coastal Research, Helmholtz-Zentrum Geesthacht, Max-Planck-Straße 1, 21502 Geesthacht, Germany
Abstract. The continually evolving large ice sheets present in the Northern Hemisphere during the last glacial cycle caused significant changes to river pathways both through directly blocking rivers and through glacial isostatic adjustment. Studies have shown these river pathway changes had a significant impact on the ocean circulation through changing the pattern of freshwater discharge into the oceans. A coupled Earth System Model (ESM) simulation of the last glacial cycle thus requires a hydrological discharge model that uses a set of river pathways that evolve with Earth's changing orography while being able to reproduce the known present-day river network given the present-day orography. Here we present a method for dynamically modelling river pathways that meets such requirements by applying pre-defined corrections to an evolving fine scale orography (accounting for the changing ice sheets and isostatic rebound) each time the river directions are recalculated. The corrected orography thus produced is then used to create a set of fine scale river pathways and these are then upscaled to a coarser scale on which an existing present-day hydrological discharge model within the JSBACH land surface model simulates the river flow. Tests show that this procedure reproduces the known present-day river network to a sufficient degree of accuracy and is able to simulate plausible paleo river networks. It has also been shown this procedure can be run successfully multiple times as part of a transient coupled climate model simulation.
Citation: Riddick, T., Brovkin, V., Hagemann, S., and Mikolajewicz, U.: Dynamic hydrological discharge modelling for coupled climate model simulations of the last glacial cycle, Geosci. Model Dev. Discuss., https://doi.org/10.5194/gmd-2018-10, in review, 2018.
Thomas Riddick et al.
Thomas Riddick et al.

Model code and software

Dynamic Hydrological Discharge Modelling Code T. Riddick https://doi.org/10.5281/zenodo.1208067
Thomas Riddick et al.

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Short summary
During the last glacial maximum, many rivers were blocked by the presence of large ice sheets and thus found new routes to the sea. This resulted in changes in the pattern of freshwater discharge into the oceans and thus would have significantly affected ocean circulation. Also, rivers found routes across the vast exposed continental shelves to the lower coastlines of that time. We propose a model for such changes in river routing suitable for use in wider models of the last glacial cycle.
During the last glacial maximum, many rivers were blocked by the presence of large ice sheets...
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