Does the atmosphere drive summer SST anomalies in southern Bay of Biscay?
- 1University of the Basque Country UPV/EHU, Faculty of Science and Technology, Dept. of Physics, Sarriena Auzoa z/g, 48940-Leioa, Spain (jon.saenz@ehu.eus)
- 2Plentziako Itsas Estazioa (BEGIK), University of the Basque Country (UPV/EHU), Areatza Hiribidea 47, 48620 Plentzia, Spain
- 3Department of Mathematics, University of the Basque Country (UPV/EHU), Paseo de la Universidad, 01006 Vitoria-Gasteiz, Spain
- 4Energy Engineering Department, University of the Basque Country (UPV/EHU), Alda, Urkijo, 48013 Bilbao, Spain
- 5Energy Engineering Department, University of the Basque Country (UPV/EHU), Europa Plaza 1, 20018 Donostia-San Sebastian, Spain
- 6AZTI, Marine Research Division - Basque Research and Technology Alliance (BRTA), Herrera Kaia, Portualdea z/g, 20110 Pasaia, Spain
During the last few years, observations show that summer warm Sea Surface Temperature (SST) records are more frequently exceeded than cold ones over the southern Bay of Biscay (SBoB). During warm years over land (for instance, summer 2023), it might be expected that atmosphere-ocean energy fluxes drive SBoB’s SST anomalies.
We explore this issue by analyzing satellite-derived (MODIS) and Optimum interpolated SST datasets. We focus on daily data (2000-2023 for MODIS and 1981-2023 for OISST) over spatially-averaged open-ocean data in SBoB, with a mask constructed from satellite pixels with SST higher than or equal to 20 ºC during August and located at least 10 km away from the coast.
We intercompare the representation of SST by those datasets. Next, we use data from reanalyses (ERA5 for atmosphere-ocean energy fluxes and Iberian-Atlantic ocean reanalysis from CMEMS for mixed layer depth and salinity) to estimate the linear relationship between the derivative with time of spatially averaged SST and surface energy fluxes. This way, the amount of variance that can be explained by the atmosphere alone is computed.
Results show that the MODIS NSST product is colder than SST4 and SST, but during summer, all of them (and OISST) are very similar. The time derivative of SST from MODIS and OISST, however, show differences. The time derivative calculated from OISS, is better suited for the calculation of the relationship with energy fluxes. The application of a multiple linear regression model to the principal components computed from daily averaged surface turbulent latent and sensible heat fluxes and shortwave and longwave radiation shows that the atmosphere is at most able to explain a 29% of the total variance during august between 2000 and 2023. This result suggests that the sea surface warming has been likely driven by a combination of atmospheric forcing and oceanic advective processes.
How to cite: Saenz, J., Carreno-Madinabeitia, S., Ibarra-Berastegi, G., Esnaola, G., and Fontán, A.: Does the atmosphere drive summer SST anomalies in southern Bay of Biscay?, EMS Annual Meeting 2024, Barcelona, Spain, 1–6 Sep 2024, EMS2024-728, https://doi.org/10.5194/ems2024-728, 2024.
