Past and future response of the North Atlantic warming hole to anthropogenic forcing

• Published in: Earth System Dynamics
• Main Author: Qasmi, Saïd
• Other Authors: Centre national de recherches météorologiques (CNRM), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales Toulouse (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales Toulouse (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France-Centre National de la Recherche Scientifique (CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2023
• Subjects: [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology; [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; [SDU.STU.ME]Sciences of the Universe [physics]/Earth Sciences/Meteorology; North Atlantic
• Online Access: https://meteofrance.hal.science/meteo-04438876; https://meteofrance.hal.science/meteo-04438876/document; https://meteofrance.hal.science/meteo-04438876/file/esd-14-685-2023.pdf; https://doi.org/10.5194/esd-14-685-2023

International audience Abstract. Most of the North Atlantic ocean has warmed over the last decades, except a region located over the subpolar gyre, known as the North Atlantic “warming hole” (WH), where sea surface temperature (SST) has in contrast decreased. Previous assessments have attributed part of this cooling to the anthropogenic forcings (ANT) – aerosols (AER) and greenhouse gases (GHGs) – modulated by decadal internal variability. Here, I use an innovative and proven statistical method which combines climate models and observations to confirm the anthropogenic role in the cooling of the warming hole. The impact of the aerosols is an increase in SST which is opposed to the effect of GHGs. The latter largely contribute to the cooling of the warming hole over the historical period. Yet, large uncertainties remain in the quantification of the impact of each anthropogenic forcing. The statistical method is able to reduce the model uncertainty in SST over the warming hole, both over the historical and future periods with a decrease of 65 % in the short term and up to 50 % in the long term. A model evaluation validates the reliability of the obtained projections. In particular, the projections associated with a strong temperature increase over the warming hole are now excluded from the likely range obtained after applying the method.