Abstract
Climate models are important tools for investigating how the climate might change in the future, however recent observations have suggested that these models are unable to capture the overturning in subpolar North Atlantic correctly, casting doubt on their projections of the Atlantic Meridional Overturning Circulation (AMOC). Here we compare the overturning and surface water mass transformation in a set of CMIP6 models with observational estimates. There is generally a good agreement, particularly in the recent conclusion from observations that the mean overturning in the east (particularly in the Iceland and Irminger seas) is stronger than that in the Labrador Sea. The overturning in the Labrador Sea is mostly found to be small, but has a strong relationship with salinity: fresh models have weak overturning and saline models have stronger mean overturning and stronger relationships of the Labrador Sea overturning variability with the AMOC further south.We also find that the overturning reconstructed from surface flux driven water mass transformation is a good indicator of the actual overturning, though mixing can modify variability and shift signals to different density classes.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
Data availability
Data from CMIP6 models (including HadGEM3-GC3-1LL and HadGEM3-GC3-1MM) is available via the Earth System Grid Federation (ESGF) data portal.
References
Bellomo K, Angeloni M, Corti S et al (2021) Future climate change shaped by inter-model differences in Atlantic meridional overturning circulation response. Nat Commun 12:3659. https://doi.org/10.1038/s41467-021-24015-w
Bentsen M, Oliviè DJL, Seland y, et al (2019) NCC NorESM2-MM model output prepared for CMIP6 CMIP piControl. https://doi.org/10.22033/ESGF/CMIP6.8221
Boucher O, Denvil S, Levavasseur G, et al (2018) IPSL IPSL-CM6A-LR model output prepared for CMIP6 CMIP piControl. https://doi.org/10.22033/ESGF/CMIP6.5251
de Boyer Montégut C, Madec G, Fischer AS et al (2004) Mixed layer depth over the global ocean: an examination of profile data and a profile-based climatology. J. Geophys. Res. Oceans 109:C12. https://doi.org/10.1029/2004JC002378
Bruggemann N, Katsman CA (2019) Dynamics of downwelling in an eddying marginal sea: contrasting the eulerian and the isopycnal perspective. https://doi.org/10.1175/JPO-D-19-0090.1
Cabanes C, Grouazel A, von Schuckmann MK, Hamon, et al (2013) The CORA dataset: validation and diagnostics of in-situ ocean temperature and salinity measurements. Ocean Sci 9:1–18. https://doi.org/10.5194/os-9-1-2013
Chafik L, Rossby T (2019) Volume, heat and freshwater divergences in the subpolar north Atlantic suggest the Nordic seas as key to the state of the meridional overturning circulation. Geophys Res Lett. https://doi.org/10.1029/2019GL082110
Danabasoglu G, Yeager SG, Bailey D et al (2014) North Atlantic simulations in coordinated ocean-ice reference experiments phase II (core-II). Part I: Mean states. Ocean Modell 73:76–107. https://doi.org/10.1016/j.ocemod.2013.10.005
Danabasoglu G, Yeager SG, Kim WM et al (2016) North Atlantic simulations in Coordinated Ocean-ice Reference Experiments phase II (CORE-II). Part II: Inter-annual to decadal variability. Ocean Model 97:65–90. https://doi.org/10.1016/j.ocemod.2015.11.007
Desbruyères D, Mercier H, Maze G et al (2019) Surface predictor of overturning circulation and heat content change in the subpolar north Atlantic. Ocean Sci 15:809–817. https://doi.org/10.5194/os-15-809-2019
Dix M, Bi D, Dobrohotoff P, et al (2019) CSIRO-ARCCSS ACCESS-CM2 model output prepared for CMIP6 CMIP piControl. https://doi.org/10.22033/ESGF/CMIP6.4311
EC-Earth Consortium (EC-Earth) (2019) EC-Earth-Consortium EC-Earth3-Veg model output prepared for CMIP6 CMIP piControl. https://doi.org/10.22033/ESGF/CMIP6.4848
Fox-Kemper B, Adcroft A, Böning C et al (2019) Challenges and prospects in ocean circulation models. Front Mar Sci. https://doi.org/10.3389/fmars.2019.00065
Good SA, Martin MJ, Rayner NA (2013) EN4: quality controlled ocean temperature and salinity profiles and monthly objective analyses with uncertainty estimates. J Geophys Res 118:6704–6716
Grist JP, Marsh R, Josey SA (2009) On the relationship between the north Atlantic meridional overturning circulation and the surface-forced overturning streamfunction. J Clim 22(19):4989–5002. https://doi.org/10.1175/2009JCLI2574.1
Grist JP, Josey SA, Marsh R (2012) Surface estimates of the Atlantic overturning in density space in an eddy-permitting ocean model. J Geophys Res 117(C06):012. https://doi.org/10.1029/2011JC007752
Groeskamp S, Griffies SM, Iudicone D et al (2019) The water mass transformation framework for ocean physics and biogeochemistry. Annu Rev Mar Sci 11(1):271–305. https://doi.org/10.1146/annurev-marine-010318-095421
Heuzé C (2017) North Atlantic deep water formation and AMOC in cmip5 models. Ocean Sci 13(4):609–622. https://doi.org/10.5194/os-13-609-2017
Jackson LC, Roberts MJ, Hewitt HT et al (2020) Impact of ocean resolution and mean state on the rate of amoc weakening. Clim Dyn 55(7):1711–1732. https://doi.org/10.1007/s00382-020-05345-9
Josey SA, Grist JP, Marsh R (2009) Estimates of meridional overturning circulation variability in the north Atlantic from surface density flux fields. J Geophys Res 114(C09):022. https://doi.org/10.1029/2008JC005230
Kalnay E, Kanamitsu M, Kistler R et al (1996) The NCEP/NCAR 40-year reanalysis project. Bull Am Meteorol Soc 77(3):437–472. https://doi.org/10.1175/1520-0477(1996)0770437:TNYRP2.0.CO;2
Katsman CA, Drijfhout SS, Dijkstra HA et al (2018) Sinking of dense north Atlantic waters in a global ocean model: location and controls. J Geophys Res Oceans 123:3563–3576. https://doi.org/10.1029/2017JC013329
Kim W, Yeager S, Danabasoglu G (2020) Atlantic multidecadal variability and associated climate impacts initiated by ocean thermohaline dynamics. J Clim 33:1317–1334. https://doi.org/10.1175/JCLI-D-19-0530.1
Koenigk T, Fuentes-Franco R, Meccia VL et al (2021) Deep mixed ocean volume in the Labrador sea in highresmip models. Clim Dyn 57(7):1895–1918. https://doi.org/10.1007/s00382-021-05785-x
Kostov Y, Johnson HL, Marshall DP (2019) Amoc sensitivity to surface buoyancy fluxes: the role of air-sea feedback mechanisms. Clim Dyn 53(7):4521–4537. https://doi.org/10.1007/s00382-019-04802-4
Kuhlbrodt T, Jones CG, Sellar A et al (2018) The low-resolution version of hadgem3 gc3.1: development and evaluation for global climate. J Adv Model Earth Syst 10:2865–2888. https://doi.org/10.1029/2018MS001370
Langehaug HR, Rhines PB, Eldevik T et al (2012) Water mass transformation and the north Atlantic current in three multicentury climate model simulations. J Geophys Res 117(C11):001. https://doi.org/10.1029/2012JC008021
Le Bras IA, Straneo F, Holte J et al (2020) Rapid export of waters formed by convection near the Irminger sea’s western boundary. Geophys Res Lett 47:e2019GL085,989. https://doi.org/10.1029/2019GL085989
Legg S, Jackson L, Hallberg RW (2008) Eddy-resolving modeling of overflows, American Geophysical Union (AGU), pp 63–81. https://doi.org/10.1029/177GM06
Li F, Lozier MS, Danabasoglu G et al (2019) Local and downstream relationships between labrador sea water volume and north Atlantic meridional overturning circulation variability. J Clim. https://doi.org/10.1175/JCLI-D-18-0735.1
Li F, Lozier M, Bacon S et al (2021) Subpolar north Atlantic western boundary density anomalies and the meridional overturning circulation. Nat Commun 12:3002. https://doi.org/10.1038/s41467-021-23350-2
Lozier MS, Li F, Bacon S et al (2019) A sea change in our view of overturning in the subpolar north Atlantic. Science 363(6426):516–521. https://doi.org/10.1126/science.aau6592
Mackay N, Wilson C, Holliday N et al (2020) The observation-based application of a regional thermohaline inverse method to diagnose the formation and transformation of water masses north of the osnap array from 2013 to 2015. J Phys Oceanogr 50:1533–1555. https://doi.org/10.1175/JPO-D-19-0188.1
Madec G (2008) NEMO ocean engine. Institut Pierre-Simon Laplace, France
Marsh R (2000) Recent variability of the north atlantic thermohaline circulation inferred from surface heat and freshwater fluxes. J Clim 13(18):3239–3260. https://doi.org/10.1175/1520-0442(2000)0133239:RVOTNA2.0.CO;2
McDougall TJ (1987) Thermobaricity, cabbeling, and water-mass conversion. J Geophys Res Oceans 92(C5):5448–5464. https://doi.org/10.1029/JC092iC05p05448
Megann A, Blaker A, Josey S et al (2021) Mechanisms for late 20th and early 21st century decadal amoc variability. J Geophys Res Oceans 126:e2021JC017,865. https://doi.org/10.1029/2021JC017865
Menary M, Jackson L, Lozier M (2020) Reconciling the relationship between the amoc and Labrador sea in OSNAP observations and climate models. Geophys Res Lett 47:2020GL089,e793. https://doi.org/10.1029/2020GL089793
Menary MB, Hodson DLR, Robson JI et al (2015) Exploring the impact of cmip5 model biases on the simulation of north Atlantic decadal variability. Geophys Res Lett 42:5926–5934. https://doi.org/10.1002/2015GL064360
Oldenburg D, Wills R, Armour K et al (2021) Mechanisms of low-frequency variability in north atlantic ocean heat transport and amoc. J Clim 34(12):4733–4755. https://doi.org/10.1175/JCLI-D-20-0614.1
Ortega P, Robson JI, Menary M et al (2021) Labrador sea subsurface density as a precursor of multidecadal variability in the north atlantic: a multi-model study. Earth Syst Dyn 12(2):419–438. https://doi.org/10.5194/esd-12-419-2021
Osterhus S, Woodgate R, Valdimarsson H et al (2019) Arctic mediterranean exchanges: a consistent volume budget and trends in transports from two decades of observations. Ocean Sci 15(2):379–399. https://doi.org/10.5194/os-15-379-2019
Petit T, Lozier MS, Josey SA et al (2020) Atlantic deep water formation occurs primarily in the iceland basin and irminger sea by local buoyancy forcing. Geophys Res Lett 47:e2020GL091,028. https://doi.org/10.1029/2020GL091028
Petit T, Lozier M, Josey S et al (2021) Role of air-sea fluxes and ocean surface density in the production of deep waters in the eastern subpolar gyre of the north atlantic. Ocean Sci 17:1353–1365. https://doi.org/10.5194/os-17-1353-2021
Pickart RS, Spall MA (2007) Impact of labrador sea convection on the north atlantic meridional overturning circulation. J Phys Oceanogr 37(9):2207–2227. https://doi.org/10.1175/JPO3178.1
Rayner NA, Parker DE, Horton EB et al (2003) Global analyses of sea surface temperature, sea ice, and night marine air temperature since the late nineteenth century. J Geophys Res 108:4407. https://doi.org/10.1029/2002JD002670
Roberts CD, Garry FK, Jackson LC (2013) A multimodel study of sea surface temperature and subsurface density fingerprints of the atlantic meridional overturning circulation. J Clim 26(22):9155–9174. https://doi.org/10.1175/jcli-d-12-00762.1
Robson J, Sutton R, Lohmann K et al (2012) Causes of the rapid warming of the North Atlantic Ocean in the mid-1990s. J Clim 25(12):4116–4134. https://doi.org/10.1175/jcli-d-11-00443.1
Sarafanov A, Falina A, Mercier H et al (2012) Mean full-depth summer circulation and transports at the northern periphery of the atlantic ocean in the 2000s. J Geophys Res Oceans 117(C01):014. https://doi.org/10.1029/2011JC007572
Sgubin G, Swingedouw D, Drijfhout S et al (2017) Abrupt cooling over the North Atlantic in modern climate models. Nat Commun 8:25
Sidorenko D, Danilov S, Fofonova V et al (2020) Amoc, water mass transformations, and their responses to changing resolution in the finite-volume sea ice-ocean model. J Adv Model Earth Syst 12:e2020MS002,317. https://doi.org/10.1029/2020MS002317
Sidorenko D, Danilov S, Streffing J et al (2021) Amoc variability and watermass transformations in the AWI climate model. J Adv Model Earth Syst 13:e2021MS002,582. https://doi.org/10.1029/2021MS002582
Swart NC, Cole JN, Kharin VV et al (2019) CCCma CanESM5 model output prepared for CMIP6 CMIP piControl. https://doi.org/10.22033/ESGF/CMIP6.3673
Tagklis F, Bracco A, Ito T et al (2020) Submesoscale modulation of deep water formation in the labrador sea. Sci Rep 10(1):17489. https://doi.org/10.1038/s41598-020-74345-w
Talandier C, Deshayes J, Treguier AM et al (2014) Improvements of simulated western north atlantic current system and impacts on the amoc. Ocean Modell 76:1–19. https://doi.org/10.1016/j.ocemod.2013.12.007
Voldoire A (2018) CMIP6 simulations of the CNRM-CERFACS based on CNRM-CM6-1 model for CMIP experiment piControl. https://doi.org/10.22033/ESGF/CMIP6.4163
Weijer W, Cheng W, Garuba O et al (2020) Cmip6 models predict significant 21st century decline of the atlantic meridional overturning circulation. Geophys Res Lett. https://doi.org/10.1029/2019GL086075
Wieners KH, Giorgetta M, Jungclaus J, et al (2019) MPI-M MPI-ESM1.2-LR model output prepared for CMIP6 CMIP piControl. https://doi.org/10.22033/ESGF/CMIP6.6675
Williams KD, Copsey D, Blockley EW et al (2018) The met office global coupled model 3.0 and 3.1 (GC3.0 and GC3.1) configurations. J Adv Model Earth Syst 10(2):357–380. https://doi.org/10.1002/2017ms001115
Wu Y, Stevens DP, Renfrew IA et al (2021) The response of the nordic seas to wintertime sea ice retreat. J Clim 34(15):6041–6056. https://doi.org/10.1175/JCLI-D-20-0932.1
Xu X, Rhines P, Chassignet E (2018) On mapping the diapycnal water mass transformation of the upper north atlantic ocean. J Phys Oceanogr 48:2233–2258. https://doi.org/10.1175/JPO-D-17-0223.1
Yeager S, Danabasoglu G (2012) Sensitivity of atlantic meridional overturning circulation variability to parameterized nordic sea overflows in ccsm4. J Clim 25(6):2077–2103. https://doi.org/10.1175/JCLI-D-11-00149.1
Yeager S, Danabasoglu G (2014) The origins of late-twentieth-century variations in the large-Scale North Atlantic circulation. J Clim 27(9):3222–3247. https://doi.org/10.1175/jcli-d-13-00125.1
Yeager S, Castruccio F, Chang P et al (2021) An outsized role for the labrador sea in the multidecadal variability of the atlantic overturning circulation. Sci Adv 7:41. https://doi.org/10.1126/sciadv.abh3592
Yukimoto S, Koshiro T, Kawai H, et al (2019) MRI MRI-ESM2.0 model output prepared for CMIP6 CMIP piControl. https://doi.org/10.22033/ESGF/CMIP6.6900
Zhang R, Delworth TL, Rosati A et al (2011) Sensitivity of the north atlantic ocean circulation to an abrupt change in the nordic sea overflow in a high resolution global coupled climate model. J Geophys Res Oceans 116:C12. https://doi.org/10.1029/2011JC007240
Zhang R, Sutton R, Danabasoglu G et al (2019) A review of the role of the atlantic meridional overturning circulation in atlantic multidecadal variability and associated climate impacts. Rev Geophys 57:316–375. https://doi.org/10.1029/2019RG000644
Zou S, Lozier M, Li F et al (2020) Density-compensated overturning in the labrador sea. Nat Geosci 13:121–126. https://doi.org/10.1038/s41561-019-0517-1
Funding
Laura Jackson was supported by the Met Office Hadley Centre Climate Programme funded by BEIS. Tillys Petit was supported by the UKRI-NERC SNAP-DRAGON (NE/T013494/1) project.
Author information
Authors and Affiliations
Contributions
LJ performed analysis of models and wrote the manuscript. TP provided observational data and commented on the manuscript. Both authors read and approved the final manuscript.
Corresponding author
Ethics declarations
Conflict of interest
The authors have no relevant financial or non-financial interests to disclose.
Additional information
Publisher's Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Rights and permissions
Springer Nature or its licensor holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.
