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search.filters.applied.f.access: openAccess × End date: 2023 × Start date: 2020 × DDC: 550 × Has files: Yes × Publisher: Amsterdam [u.a.] : Elsevier Science × WGL Institute: PIK ×

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    Vertical processes and resolution impact ice shelf basal melting: A multi-model study
    (Amsterdam [u.a.] : Elsevier Science, 2020) Gwyther, David E.; Kusahara, Kazuya; Asay-Davis, Xylar S.; Dinniman, Michael S.; Galton-Fenzi, Benjamin K.
    Understanding ice shelf–ocean interaction is fundamental to projecting the Antarctic ice sheet response to a warming climate. Numerical ice shelf–ocean models are a powerful tool for simulating this interaction, yet are limited by inherent model weaknesses and scarce observations, leading to parameterisations that are unverified and unvalidated below ice shelves. We explore how different models simulate ice shelf–ocean interaction using the 2nd Ice Shelf–Ocean Model Intercomparison Project (ISOMIP+) framework. Vertical discretisation and resolution of the ocean model are shown to have a significant effect on ice shelf basal melt rate, through differences in the distribution of meltwater fluxes and the calculation of thermal driving. Z-coordinate models, which generally have coarser vertical resolution in ice shelf cavities, may simulate higher melt rates compared to terrain-following coordinate models. This is due to the typically higher resolution of the ice–ocean boundary layer region in terrain following models, which allows better representation of a thin meltwater layer, increased stratification, and as a result, better insulation of the ice from water below. We show that a terrain-following model, a z-level coordinate model and a hybrid approach give similar results when the effective vertical resolution adjacent to the ice shelf base is similar, despite each model employing different paradigms for distributing meltwater fluxes and sampling tracers for melting. We provide a benchmark for thermodynamic ice shelf–ocean interaction with different model vertical coordinates and vertical resolutions, and suggest a framework for any future ice shelf–ocean thermodynamic parameterisations. © 2020 The Authors
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    Disentangling diverse responses to climate change among global marine ecosystem models
    (Amsterdam [u.a.] : Elsevier Science, 2021) Heneghan, Ryan F.; Galbraith, Eric; Blanchard, Julia L.; Harrison, Cheryl; Barrier, Nicolas; Bulman, Catherine; Cheung, William; Coll, Marta; Eddy, Tyler D.; Erauskin-Extramiana, Maite; Everett, Jason D.; Fernandes-Salvador, Jose A.; Gascuel, Didier; Guiet, Jerome; Maury, Olivier; Palacios-Abrantes, Juliano; Petrik, Colleen M.; du Pontavice, Hubert; Richardson, Anthony J.; Steenbeek, Jeroen; Tai, Travis C.; Volkholz, Jan; Woodworth-Jefcoats, Phoebe A.; Tittensor, Derek P.
    Climate change is warming the ocean and impacting lower trophic level (LTL) organisms. Marine ecosystem models can provide estimates of how these changes will propagate to larger animals and impact societal services such as fisheries, but at present these estimates vary widely. A better understanding of what drives this inter-model variation will improve our ability to project fisheries and other ecosystem services into the future, while also helping to identify uncertainties in process understanding. Here, we explore the mechanisms that underlie the diversity of responses to changes in temperature and LTLs in eight global marine ecosystem models from the Fisheries and Marine Ecosystem Model Intercomparison Project (FishMIP). Temperature and LTL impacts on total consumer biomass and ecosystem structure (defined as the relative change of small and large organism biomass) were isolated using a comparative experimental protocol. Total model biomass varied between −35% to +3% in response to warming, and -17% to +15% in response to LTL changes. There was little consensus about the spatial redistribution of biomass or changes in the balance between small and large organisms (ecosystem structure) in response to warming, an LTL impacts on total consumer biomass varied depending on the choice of LTL forcing terms. Overall, climate change impacts on consumer biomass and ecosystem structure are well approximated by the sum of temperature and LTL impacts, indicating an absence of nonlinear interaction between the models’ drivers. Our results highlight a lack of theoretical clarity about how to represent fundamental ecological mechanisms, most importantly how temperature impacts scale from individual to ecosystem level, and the need to better understand the two-way coupling between LTL organisms and consumers. We finish by identifying future research needs to strengthen global marine ecosystem modelling and improve projections of climate change impacts.