Response of Arctic sea level and hydrography to hydrological regime change over boreal catchments (RASLyBoCa)

Changes in freshwater influx into the Arctic Ocean are a key driver of regional dynamics and sea level change in the Arctic waters. Fresh surface waters maintain a strong stratification in the Arctic. This halocline largely shields the cool polar surface water and sea ice from the warmer waters of Atlantic origin below and hence inhibits vertical heat fluxes. Changes in the freshwater content are likely to affect regional steric sea level, but also the modified ocean dynamics may change sea level through mass transports within the Arctic.

The hydrological regime of river runoff appears to be non-stationary. However, the observational record of discharge into the Arctic Ocean is still too sparse to address important science questions into the long-term behaviour and development of Arctic sea level and climate.


Apart from in-situ observations and hydrological models, satellite gravimetry (GRACE) and satellite altimetry open up additional new avenues of observing the hydrology of large catchments literally by measuring the water storage over catchments and water level along rivers, which can be transformed into discharge through several methods. For ice-ocean models, the sparsity of runoff information (in the Arctic) generally requires that the seasonal cycle of runoff is assumed to the stationary. Here we propose to lift this assumption. We propose to use an ice-ocean general circulation model to study the impact of interannually varying runoff on the Arctic circulation and freshwater budget. This project will contribute to “mechanisms of sea level variability” and “local projections of sea level trends”. The main objective of the proposed study is to assess and quantify the response of Arctic sea level and hydrography to hydrological regime change over boreal catchments. The project objectives contribute to the strategy of the Priority Research Programme 1889 by

  • Improving the observational record of hydrological parameters over boreal catchments by geodetic spaceborne methods (time varying gravimetry, satellite altimetry). Achieving long and dense time series of runoff for all major catchments draining into the Arctic Ocean.

  • Sensitivity analysis of sea ice and ocean dynamics to changes in freshwater forcing (including runoff). To this end a pan-Arctic model will be configured and methods of forward perturbations (stationary vs. interannually varying runoff) will be combined with adjoint methods, where the sensitivity of global objective functions, e.g. global or regional freshwater content or sea level, to all forcing parameters is assessed through single adjoint model simulations.

  • Comparison of model output in relation to changes in continental runoff with observed variability of liquid freshwater content (and resulting steric height changes) in the Arctic Ocean and the North Atlantic since 1990. Not only do these comparisons serve as model evaluation, but they will also help interpreting comparatively sparse oceanographic in-situ records.

  • The aforementioned objectives address the following work programmes of SPP1889:

RASLyBoCa: objectives and tasks

The RASLyBoCa project is also a member of the Focusgroup Cryosphere and Sea Level (FCS).

Principal Investigators:

 

Dr.-Ing. Mohammad J. Tourian

University of Stuttgart, Institute of Geodesy (GIS)

Geschwister-Scholl-Str. 24D

70174 Stuttgart, Germany

Tel: +49 0711 685-83474, 0711 685-83285

Email: tourian(at)gis.uni-stuttgart.de

 

Prof. Dr.-Ing. Nico Sneeuw

Universität Stuttgart, Institute of Geodesy (GIS)

Geschwister-Scholl-Str. 24D

70174 Stuttgart, Germany

Tel: +49 0711 685-83390, 0711 685-83285

Email: sneeuw(at)gis.uni-stuttgart.de

 

Dr. Martin Losch

Senior Research Scientist

Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung, Klimawissenschaften

Am Handelshafen 12

27574 Bremerhaven, Germany

Tel: +49 0471 4831-1872, 0471 4831-1797

Email: Martin.Losch(at)awi.de

 

Dr. Benjamin Rabe

Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung, Klimawissenschaften

Am Handelshafen 12

27574 Bremerhaven, Germany

Tel: +49 0471 4831-2403, 0471 4831-1797

Email: Benjamin.Rabe(at)awi.de

 

PhD Students:

 

Elena Gerwing

Alfred-Wegener-Institut

Helmholtz-Zentrum für Polar- und Meeresforschung, Klimawissenschaften

Am Handelshafen 12

27574 Bremerhaven, Germany

Tel: +49 0471 4831-1720, 0471 4831-1149

Email: Elena.Gerwing(at)awi.de

 

Elisabeth Woisetschläger, MSc.

Universität Stuttgart, Institute of Geodesy (GIS)

Geschwister-Scholl-Str. 24D

70174 Stuttgart

Tel.: +49 0711 685-84638, 0711 685-83285

Email: elisabeth.woisetschlaeger(at)gis.uni-stuttgart.de