Impact of marine heatwaves on air-sea carbon dioxide flux in the Northwest Atlantic coastal margins
Date
2023
Authors
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Publisher
University of Delaware
Abstract
The sensitivity of the carbonate system to sea surface temperature variability suggests that extreme temperatures during marine heatwave (MHW) events could modulate the transfer of carbon between the atmosphere and ocean. To investigate this, I quantified the influence of MHW events on air-sea CO2 flux anomalies (FCO2’) in the Mid Atlantic Bight (MAB) and South Atlantic Bight (SAB) from 1992-2020. I first investigated the FCO2 changes during the longest MHW events in the MAB and SAB, respectively, before examining FCO2 changes during the ensemble of all MHW months in each region. Results show that MHWs primarily generated positive sea surface pCO2 anomalies (pCO2sea’) and had a larger impact on FCO2’ in the MAB. These positive anomalies attempt to reduce CO2 uptake during sink months and enhance outgassing during source months. While MHWs also aided in the creation of large positive FCO2’ values in the SAB, non-thermal drivers dominated pCO2sea’ values and therefore FCO2’ during MHWs. However, not all MHWs produced a large, positive FCO2’. For MHW influences to be reflected in FCO2’ values, both MHW and non-thermal drivers of pCO2sea’ must provide positive contributions to pCO2sea’. Otherwise, non-thermal drivers tended to counteract the influence of MHWs. Wind speed contributions were of secondary importance as FCO2’ drivers, but slower wind speeds were found to amplify the influence of MHWs on FCO2’ in winter months but reduce it in summer months. This work provides an important first look at the impact of MHW events on FCO2 in the northwest Atlantic coastal margin, bridging the gap between extreme SST events and the coastal carbonate system.
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Keywords
Air-sea flux, Marine heatwave events, US East Coast, Atlantic coastal margin