MARC

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022 |a 2190-4979 
022 |a 2190-4987 
024 7 |a 10.5194/esd-16-379-2025  |2 doi 
035 |a 3174360607 
045 2 |b d20250101  |b d20251231 
084 |a 262941  |2 nlm 
100 1 |a Bauer, Victoria M  |u Institute for Atmospheric and Climate Science, ETH Zürich, Zurich, Switzerland 
245 1 |a Impacts of North American forest cover changes on the North Atlantic Ocean circulation 
260 |b Copernicus GmbH  |c 2025 
513 |a Journal Article 
520 3 |a Planetary-scale forestation has been shown to induce global surface warming associated with a slowdown of the Atlantic Meridional Overturning Circulation (AMOC). This AMOC slowdown is accompanied by a negative North Atlantic sea surface temperature (SST) anomaly resembling the known North Atlantic warming hole found in greenhouse gas forcing simulations. Likewise, a reversed equivalent of the SST response has been found across deforestation experiments. Here, we test the hypothesis that localised forest cover changes over North America are an important driver of this response in the downstream North Atlantic Ocean. Moreover, we shine a light on the physical processes linking forest cover perturbations to ocean circulation changes. To this end, we perform simulations using the fully coupled Earth system model CESM2, where pre-industrial vegetation-sustaining areas over North America are either completely forested (“forestNA”) or turned into grasslands (“grassNA”). Our results show that North American forest cover changes have the potential to alter the AMOC and North Atlantic SSTs in a manner similar to global ones. North American forest cover changes mainly impact the ocean circulation through modulating land surface albedo and, subsequently, air temperatures. We find that comparably short-lived cold-air outbreaks (CAOs) play a crucial role in transferring the signal from the land to the ocean. Around 80 % of the ocean heat loss in the Labrador Sea occurs within CAOs during which the atmosphere is colder than the underlying ocean. A warmer atmosphere in forestNA compared to the “control” scenario results in fewer CAOs over the ocean and thereby reduced ocean heat loss and deep convection, with the opposite being true for grassNA. The induced SST responses further decrease CAO frequency in forestNA and increase it in grassNA. Lagrangian backward trajectories starting from CAOs over the Labrador Sea confirm that their source regions include (de-)forested areas. Furthermore, the subpolar gyre circulation is found to be more sensitive to ocean density changes driven by heat fluxes than to changes in wind forcing modulated by upstream land surface roughness. In forestNA, sea ice growth and the corresponding further reduction in ocean-to-atmosphere heat fluxes forms an additional positive feedback loop. Conversely, a buoyancy flux decomposition shows that freshwater forcing only plays a minor role in the ocean density response in both scenarios. Overall, this study shows that the North Atlantic Ocean circulation is particularly sensitive to upstream forest cover changes and that there is a self-enhancing feedback between CAO frequencies, deep convection, and SSTs in the North Atlantic. This motivates studying the relative importance of these high-frequency atmospheric events for ocean circulation changes in the context of anthropogenic climate change. 
651 4 |a North America 
651 4 |a United States--US 
651 4 |a Canada 
651 4 |a Quebec Canada 
651 4 |a Great Plains 
651 4 |a Atlantic Ocean 
653 |a Forests 
653 |a Sea surface temperature 
653 |a Deforestation 
653 |a Upstream 
653 |a Sea ice 
653 |a Grasslands 
653 |a Air temperature 
653 |a Heat 
653 |a Surface roughness 
653 |a Human influences 
653 |a Buoyancy flux 
653 |a Greenhouse effect 
653 |a Vegetation 
653 |a Control theory 
653 |a Cooling 
653 |a Positive feedback 
653 |a Carbon 
653 |a Heat loss 
653 |a Atlantic Meridional Overturning Circulation (AMOC) 
653 |a Climate change 
653 |a Surface temperature 
653 |a Convection 
653 |a Circulation 
653 |a Feedback loops 
653 |a Greenhouse gases 
653 |a Temperature 
653 |a Pest outbreaks 
653 |a Heat transfer 
653 |a Atmosphere 
653 |a Albedo 
653 |a Inland water environment 
653 |a Ocean currents 
653 |a Density 
653 |a Simulation 
653 |a Ocean circulation 
653 |a Experiments 
653 |a Heat flux 
653 |a Sea ice growth 
653 |a Anthropogenic climate changes 
653 |a Feedback 
653 |a Water circulation 
653 |a Oceans 
653 |a Anthropogenic factors 
653 |a Freshwater 
653 |a Land use 
653 |a Hypothesis testing 
653 |a Environmental 
700 1 |a Schemm, Sebastian  |u Institute for Atmospheric and Climate Science, ETH Zürich, Zurich, Switzerland 
700 1 |a Portmann, Raphael  |u Climate and Agriculture, Division of Agroecology and Environment, Agroscope Reckenholz, Zurich, Switzerland; present address: planval, Bern, Switzerland 
700 1 |a Zhang, Jingzhi  |u Institute for Atmospheric and Climate Science, ETH Zürich, Zurich, Switzerland 
700 1 |a Eirund, Gesa K  |u Institute for Biogeochemistry and Pollutant Dynamics, ETH Zürich, Zurich, Switzerland 
700 1 |a De Hertog, Steven J  |u Department of Water and Climate, Vrije Universiteit Brussel, Brussels, Belgium; Q-ForestLab, Department of Environment, Universiteit Gent, Ghent, Belgium 
700 1 |a Zibell, Jan  |u Institute for Atmospheric and Climate Science, ETH Zürich, Zurich, Switzerland 
773 0 |t Earth System Dynamics  |g vol. 16, no. 2 (2025), p. 379 
786 0 |d ProQuest  |t Publicly Available Content Database 
856 4 1 |3 Citation/Abstract  |u https://www.proquest.com/docview/3174360607/abstract/embedded/9R349J4AAH19K9LJ?source=fedsrch 
856 4 0 |3 Full Text  |u https://www.proquest.com/docview/3174360607/fulltext/embedded/9R349J4AAH19K9LJ?source=fedsrch 
856 4 0 |3 Full Text - PDF  |u https://www.proquest.com/docview/3174360607/fulltextPDF/embedded/9R349J4AAH19K9LJ?source=fedsrch