Exploring the climate system response to a range of freshwater representations: Hosing, Regional, and Freshwater Fingerprints

• Main Authors: Love, Ryan, Tarasov, Lev, Andres, Heather, Condron, Alan, Zhang, Xu, Lohmann, Gerrit
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2023
• Subjects: article; Verlagsveröffentlichung; Mackenzie River; Mak; Ice Sheet; Labrador Sea; Mackenzie river; North Atlantic
• Online Access: https://doi.org/10.5194/egusphere-2023-2225; https://noa.gwlb.de/receive/cop_mods_00069319; https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00067706/egusphere-2023-2225.pdf; https://egusphere.copernicus.org/preprints/2023/egusphere-2023-2225/egusphere-2023-2225.pdf

Freshwater, in the form of terrestrial runoff, is hypothesized to have played a critical role in past centennial to millennial scale climate variability by suppressing the production of deep-water in the North Atlantic. It may also play a central role in future climate change as ice sheet and glacier melt accelerates under anthropogenic climate change. In model studies of both past and future climate change, freshwater Hosing (i.e. injection across wide bands in the North Atlantic) is typically used as a means-to-an-end by inducing a strong thermohaline circulation and climate response, with little regard for the other roles that freshwater plays in a complex coupled climate environment. Herein, we evaluate the realism of Hosing relative to two more sophisticated freshwater injection methods, all under glacial boundary conditions: regional injection (allowing the relatively coarse-resolution climate model to transport the freshwater) and a novel freshwater fingerprint method. The latter approach distributes freshwater into an eddy-parametrizing ocean model based upon where it is transported to in a higher resolution eddy-permitting model. Here the COSMOS Earth system model is used as the eddy-parametrizing model, and a configuration of the MITgcm model as the eddy-permitting model. This analysis address three primary questions. Firstly, where is freshwater routed at moderate versus eddy-permitting resolution? Secondly, does the freshwater fingerprint method allow the coarser resolution model to reproduce the net-results of eddy-permitting behaviour? Thirdly, how do climate impacts vary between different forms of freshwater injection? Of the four outlets tested, we find that freshwater released at the Mackenzie River (MAK) outlet results in the most similar freshwater transport patterns at both the eddy-parametrizing and the eddy-permitting resolutions. However at eddy-permitting resolution there is a greater freshening of the contemporary Labrador Sea deep water formation region and mixing of freshwater into the ...