On the reduced sensitivity of the Atlantic overturning to Greenland ice sheet melting in projections: a multi-model assessment

Verfasser / Beitragende:
[Didier Swingedouw, Christian Rodehacke, Steffen Olsen, Matthew Menary, Yongqi Gao, Uwe Mikolajewicz, Juliette Mignot]
Ort, Verlag, Jahr:
2015
Enthalten in:
Climate Dynamics, 44/11-12(2015-06-01), 3261-3279
Format:
Artikel (online)
ID: 605474591
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024 7 0 |a 10.1007/s00382-014-2270-x  |2 doi 
035 |a (NATIONALLICENCE)springer-10.1007/s00382-014-2270-x 
245 0 0 |a On the reduced sensitivity of the Atlantic overturning to Greenland ice sheet melting in projections: a multi-model assessment  |h [Elektronische Daten]  |c [Didier Swingedouw, Christian Rodehacke, Steffen Olsen, Matthew Menary, Yongqi Gao, Uwe Mikolajewicz, Juliette Mignot] 
520 3 |a Large uncertainties exist concerning the impact of Greenland ice sheet melting on the Atlantic meridional overturning circulation (AMOC) in the future, partly due to different sensitivity of the AMOC to freshwater input in the North Atlantic among climate models. Here we analyse five projections from different coupled ocean-atmosphere models with an additional 0.1Sv (1Sv=106 m3/s) of freshwater released around Greenland between 2050 and 2089. We find on average a further weakening of the AMOC at 26°N of 1.1±0.6Sv representing a 27±14% supplementary weakening in 2080-2089, as compared to the weakening relative to 2006-2015 due to the effect of the external forcing only. This weakening is lower than what has been found with the same ensemble of models in an identical experimental set-up but under recent historical climate conditions. This lower sensitivity in a warmer world is explained by two main factors. First, a tendency of decoupling is detected between the surface and the deep ocean caused by an increased thermal stratification in the North Atlantic under the effect of global warming. This induces a shoaling of ocean deep ventilation through convection hence ventilating only intermediate levels. The second important effect concerns the so-called Canary Current freshwater leakage; a process by which additionally released freshwater in the North Atlantic leaks along the Canary Current and escapes the convection zones towards the subtropical area. This leakage is increasing in a warming climate, which is a consequence of decreasing gyres asymmetry due to changes in Ekman pumping. We suggest that these modifications are related with the northward shift of the jet stream in a warmer world. For these two reasons the AMOC is less susceptible to freshwater perturbations (near the deep water formation sides) in the North Atlantic as compared to the recent historical climate conditions. Finally, we propose a bilinear model that accounts for the two former processes to give a conceptual explanation about the decreasing AMOC sensitivity due to freshwater input. Within the limit of this bilinear model, we find that 62±8% of the reduction in sensitivity is related with the changes in gyre asymmetry and freshwater leakage and 38±8% is due to the reduction in deep ocean ventilation associated with the increased stratification in the North Atlantic. 
540 |a Springer-Verlag Berlin Heidelberg, 2014 
690 7 |a Greenland ice sheet melting  |2 nationallicence 
690 7 |a Thermohalinecirculation  |2 nationallicence 
690 7 |a Oceanic gyre  |2 nationallicence 
690 7 |a Ocean-atmosphere interactions  |2 nationallicence 
690 7 |a Oceanic dynamics  |2 nationallicence 
690 7 |a Sea-level rise  |2 nationallicence 
690 7 |a AMOC  |2 nationallicence 
690 7 |a North Atlantic  |2 nationallicence 
700 1 |a Swingedouw  |D Didier  |u EPOC laboratory, CNRS / University of Bordeaux, Allée Geoffroy Saint Hilaire, 33615, Bordeaux, France  |4 aut 
700 1 |a Rodehacke  |D Christian  |u DMI, Copenhagen, Denmark  |4 aut 
700 1 |a Olsen  |D Steffen  |u DMI, Copenhagen, Denmark  |4 aut 
700 1 |a Menary  |D Matthew  |u Hadley Centre, Exeter, UK  |4 aut 
700 1 |a Gao  |D Yongqi  |u NERSC, Bergen, Norway  |4 aut 
700 1 |a Mikolajewicz  |D Uwe  |u Max-Planck-Institut für Meteorologie, Hamburg, Germany  |4 aut 
700 1 |a Mignot  |D Juliette  |u LOCEAN Laboratory, Sorbonne Universités (UPMC, Univ Paris 06)-CNRS-IRD-MNHN, 4 Place Jussieu, Paris, France  |4 aut 
773 0 |t Climate Dynamics  |d Springer Berlin Heidelberg  |g 44/11-12(2015-06-01), 3261-3279  |x 0930-7575  |q 44:11-12<3261  |1 2015  |2 44  |o 382 
856 4 0 |u https://doi.org/10.1007/s00382-014-2270-x  |q text/html  |z Onlinezugriff via DOI 
898 |a BK010053  |b XK010053  |c XK010000 
900 7 |a Metadata rights reserved  |b Springer special CC-BY-NC licence  |2 nationallicence 
908 |D 1  |a research-article  |2 jats 
949 |B NATIONALLICENCE  |F NATIONALLICENCE  |b NL-springer 
950 |B NATIONALLICENCE  |P 856  |E 40  |u https://doi.org/10.1007/s00382-014-2270-x  |q text/html  |z Onlinezugriff via DOI 
950 |B NATIONALLICENCE  |P 700  |E 1-  |a Swingedouw  |D Didier  |u EPOC laboratory, CNRS / University of Bordeaux, Allée Geoffroy Saint Hilaire, 33615, Bordeaux, France  |4 aut 
950 |B NATIONALLICENCE  |P 700  |E 1-  |a Rodehacke  |D Christian  |u DMI, Copenhagen, Denmark  |4 aut 
950 |B NATIONALLICENCE  |P 700  |E 1-  |a Olsen  |D Steffen  |u DMI, Copenhagen, Denmark  |4 aut 
950 |B NATIONALLICENCE  |P 700  |E 1-  |a Menary  |D Matthew  |u Hadley Centre, Exeter, UK  |4 aut 
950 |B NATIONALLICENCE  |P 700  |E 1-  |a Gao  |D Yongqi  |u NERSC, Bergen, Norway  |4 aut 
950 |B NATIONALLICENCE  |P 700  |E 1-  |a Mikolajewicz  |D Uwe  |u Max-Planck-Institut für Meteorologie, Hamburg, Germany  |4 aut 
950 |B NATIONALLICENCE  |P 700  |E 1-  |a Mignot  |D Juliette  |u LOCEAN Laboratory, Sorbonne Universités (UPMC, Univ Paris 06)-CNRS-IRD-MNHN, 4 Place Jussieu, Paris, France  |4 aut 
950 |B NATIONALLICENCE  |P 773  |E 0-  |t Climate Dynamics  |d Springer Berlin Heidelberg  |g 44/11-12(2015-06-01), 3261-3279  |x 0930-7575  |q 44:11-12<3261  |1 2015  |2 44  |o 382