Gulf Stream and interior western boundary volume transport as key regions to constrain the future North Atlantic Carbon Uptake
As one of the major carbon sinks in the global ocean, the North Atlantic is a key player in mediating the ongoing global warming. However, projections of the North Atlantic carbon sink in a high-CO 2 future are highly uncertain due to greatly varying model results. A previous study analysed an ensem...
| Main Authors: | , , |
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| Format: | Text |
| Language: | English |
| Published: |
2022
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| Subjects: | |
| Online Access: | https://doi.org/10.5194/gmd-2022-152 https://gmd.copernicus.org/preprints/gmd-2022-152/ |
| Summary: | As one of the major carbon sinks in the global ocean, the North Atlantic is a key player in mediating the ongoing global warming. However, projections of the North Atlantic carbon sink in a high-CO 2 future are highly uncertain due to greatly varying model results. A previous study analysed an ensemble of 11 CMIP5-models and identified two indicators of contemporary model behavior that are highly correlated with a model´s projected future carbon-uptake in the North Atlantic: (i) the high latitude winter pCO 2 sea -anomaly, which is tightly linked to winter mixing and nutrient supply and (ii) the fraction of the anthropogenically altered carbon-inventory stored below 1000 m depth, indicating the efficiency of dissolved inorganic carbon transport into and within the deep ocean. Both relationships build so-called emergent constraints, where observed contemporary indicators can be used to improve future North Atlantic carbon sink estimates. In this study, we apply a genetic algorithm to optimize these emergent relationships by constraining the spatial extent of the indicators, i.e. to identify key regions that maximise the cross-correlations between the indicators and the future carbon uptake. We pre-define the shape of the desired regions as (i) rectangles and ellipses of different sizes for the first surface-2D indicator and (ii) cuboids and ellipsoids of different volumes for the second water column-3D indicator. Independent on shape and size, the genetic algorithm persistently identifies the Gulf Stream region as optimal for the first indicator as well as the pathway of the broad interior southward volume transport for the second indicator. This is further confirmed with high correlations between the North Atlantic future carbon uptake and volume transport values extracted for the central latitudes and depths of these optimal regions. Though the importance of volume transport for the carbon uptake is well known, our results go beyond traditional knowledge and identify which depth-ranges and latitudes of this ... |
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