Simulated and observed transport estimates across the Overturning in the Subpolar North Atlantic Program (OSNAP) sections

Gokhan Danabasoglu; Frederic S. Castruccio; Burcu Boza; Alice M. Barthel; Arne Biastoch; Adam Blaker; Alexandra Bozec; Diego Bruciaferri; Frank O. Bryan; Eric P. Chassignet; Yao Fu; Ian Grooms; Catherine Guiavarc'h; Hakase Hayashida; Andrew Mc C. Hogg; Ryan M. Holmes; Doroteaciro Iovino; Andrew E. Kiss; M. Susan Lozier; Gustavo Marques; Alex Megann; Franziska U. Schwarzkopf; Dave Storkey; Luke van Roekel; Jon Wolfe; Xiaobiao Xu; Rong Zhang

doi:10.5194/gmd-19-5071-2026

Simulated and observed transport estimates across the Overturning in the Subpolar North Atlantic Program (OSNAP) sections

Gokhan Danabasoglu
, Frederic S. Castruccio
, Burcu Boza
, Alice M. Barthel
, Arne Biastoch
, Adam Blaker
, Alexandra Bozec
, Diego Bruciaferri
, Frank O. Bryan
, Eric P. Chassignet
, Yao Fu
, Ian Grooms
, Catherine Guiavarc'h
, Hakase Hayashida
, Andrew Mc C. Hogg
, Ryan M. Holmes
, Doroteaciro Iovino
, Andrew E. Kiss
, M. Susan Lozier
, Gustavo Marques

Alex Megann, Franziska U. Schwarzkopf, Dave Storkey, Luke van Roekel, Jon Wolfe, Xiaobiao Xu, Rong Zhang

Oceanography

Istanbul Technical University
Los Alamos National Laboratory
Helmholtz Centre for Ocean Research Kiel
Kiel University
National Oceanography Centre
Florida State University
Met Office
Georgia Institute of Technology
University of South Florida
University of Colorado Boulder
Japan Agency for Marine-Earth Science and Technology
Australian National University
Bureau of Meteorology Australia
Euro-Mediterranean Center on Climate Change
Princeton University
National Oceanic and Atmospheric Administration

Research output: Contribution to journal › Article › peer-review

Abstract

A comparison of simulated and observed overturning transports and related properties across the Overturning in the Subpolar North Atlantic Program (OSNAP) sections for the 2014–2022 period is presented, considering both depth and density space transports. The effort was motivated by the observational transport estimates at both OSNAP-West (OW) and OSNAP-East (OE) sections which show a minor role for the Labrador Sea (LS) in setting the mean and variability of the overturning in the subpolar North Atlantic. There are 9 participating groups from around the world, contributing a total of 18 ocean-sea-ice simulations with 6 different ocean models. The simulations use a common set of interannually varying atmospheric forcing datasets. The horizontal resolutions of the simulations range from nominal 1° to eddy-resolving resolutions of 0.1–0.05°. While there are many differences between the simulations and observations as well as among the individual simulations in terms of transport properties, the simulations show significantly larger transports at OE than at OW in agreement with the observations. Analyzing overturning circulations in both depth and density space together provides a more complete picture of the overturning properties and features. This analysis also reveals that, in both the simulations and observations, northward and southward flows substantially cancel each other at a given depth or density, producing much smaller residual (total) transports. Such cancellations tend to be much more prominent in depth space than in density space. In general, the observed transport features are captured better at OE than OW. The simulations generally show larger (smaller) transports with positive (negative) temperature and salinity biases in the upper ocean near the OSNAP sections, but with no such relationship with density biases. In high-resolution simulations, the transport profiles agree better with the observations, but challenges remain in some other metrics considered in our analysis. When transports are calculated using a density referenced to 2000 m depth, rather than the ocean surface, the relative contributions of transports at OW increase modestly.

Original language	English
Pages (from-to)	5071-5117
Number of pages	47
Journal	Geoscientific Model Development
Volume	19
Issue number	11
DOIs	https://doi.org/10.5194/gmd-19-5071-2026
State	Published - Jun 15 2026

Funding

This effort at the US National Science Foundation (NSF) National Center for Atmospheric Research (NCAR) was supported by the contract 1947282 from the US Department of Energy (DOE) for the ImPACTS Project; by the grant NA18OAR4310429 from the US National Oceanic and Atmospheric Administration (NOAA), Climate Program Office (CPO), Climate Variability and Predictability Program; Modeling Analysis, Predictions, and Projections Program; the NOAA Global Ocean Monitoring and Observing (GOMO) Program; the DOE, Earth and Environmental System Modeling, Regional and Global Model Analysis Program; and by the grant OPP-2106228 from the US NSF Office of Polar Programs. The project was also partly funded by the US NSF Physical Oceanography Program by the grant OCE-2040020 for the US NSF - UK Natural Environment Research Council (NERC) project entitled "Wider Impacts of Subpolar North Atlantic Decadal Variability on the Ocean and Atmosphere (WISHBONE)". AEK was supported by the Australian Research Council (ARC) grant LP200100406. RMH was supported by the ARC grant DE21010004. AM was supported by the UK Natural Environment Research Council under the Atlantic Climate System Integrated Study (ACSIS; grant number NE/N018044/1) and the Climate Linked Atlantic Sector Science (CLASS; grant number NE/R015953/1) marine research programmes. ABl was supported by CLASS (NE/R015953/1) and the WISHBONE project (NE/T013540/1). BB was partly supported by the Turkish Scientific and Technological Research Council (TUBITAK) via an International Research Fellowship Programme for PhD Students (2214-A). MSL and YF acknowledge funding from the US NSF Physical Oceanography Program grant OCE-1948335.

Funders	Funder number
Office of Polar Programs	OPP-2106228
Natural Environment Research Council	n/a
National Science Foundation	A18OAR4310429
National Oceanic and Atmospheric Administration	n/a
Australian Research Council	LP200100406

Keywords

Multidecadal variability
Impact
Global ocean
Southern-ocean
Climate
General-circulation model
Sea-ice model
Experimental protocols
Part i
Ocean model

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10.5194/gmd-19-5071-2026

Cite this

Danabasoglu, G., Castruccio, F. S., Boza, B., Barthel, A. M., Biastoch, A., Blaker, A., Bozec, A., Bruciaferri, D., Bryan, F. O., Chassignet, E. P., Fu, Y., Grooms, I., Guiavarc'h, C., Hayashida, H., Hogg, A. M. C., Holmes, R. M., Iovino, D., Kiss, A. E., Lozier, M. S., ... Zhang, R. (2026). Simulated and observed transport estimates across the Overturning in the Subpolar North Atlantic Program (OSNAP) sections. Geoscientific Model Development, 19(11), 5071-5117. https://doi.org/10.5194/gmd-19-5071-2026

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title = "Simulated and observed transport estimates across the Overturning in the Subpolar North Atlantic Program (OSNAP) sections",

abstract = "A comparison of simulated and observed overturning transports and related properties across the Overturning in the Subpolar North Atlantic Program (OSNAP) sections for the 2014{\textendash}2022 period is presented, considering both depth and density space transports. The effort was motivated by the observational transport estimates at both OSNAP-West (OW) and OSNAP-East (OE) sections which show a minor role for the Labrador Sea (LS) in setting the mean and variability of the overturning in the subpolar North Atlantic. There are 9 participating groups from around the world, contributing a total of 18 ocean-sea-ice simulations with 6 different ocean models. The simulations use a common set of interannually varying atmospheric forcing datasets. The horizontal resolutions of the simulations range from nominal 1° to eddy-resolving resolutions of 0.1{\textendash}0.05°. While there are many differences between the simulations and observations as well as among the individual simulations in terms of transport properties, the simulations show significantly larger transports at OE than at OW in agreement with the observations. Analyzing overturning circulations in both depth and density space together provides a more complete picture of the overturning properties and features. This analysis also reveals that, in both the simulations and observations, northward and southward flows substantially cancel each other at a given depth or density, producing much smaller residual (total) transports. Such cancellations tend to be much more prominent in depth space than in density space. In general, the observed transport features are captured better at OE than OW. The simulations generally show larger (smaller) transports with positive (negative) temperature and salinity biases in the upper ocean near the OSNAP sections, but with no such relationship with density biases. In high-resolution simulations, the transport profiles agree better with the observations, but challenges remain in some other metrics considered in our analysis. When transports are calculated using a density referenced to 2000 m depth, rather than the ocean surface, the relative contributions of transports at OW increase modestly.",

keywords = "Multidecadal variability, Impact, Global ocean, Southern-ocean, Climate, General-circulation model, Sea-ice model, Experimental protocols, Part i, Ocean model",

author = "Gokhan Danabasoglu and Castruccio, \{Frederic S.\} and Burcu Boza and Barthel, \{Alice M.\} and Arne Biastoch and Adam Blaker and Alexandra Bozec and Diego Bruciaferri and Bryan, \{Frank O.\} and Chassignet, \{Eric P.\} and Yao Fu and Ian Grooms and Catherine Guiavarc'h and Hakase Hayashida and Hogg, \{Andrew Mc C.\} and Holmes, \{Ryan M.\} and Doroteaciro Iovino and Kiss, \{Andrew E.\} and Lozier, \{M. Susan\} and Gustavo Marques and Alex Megann and Schwarzkopf, \{Franziska U.\} and Dave Storkey and \{van Roekel\}, Luke and Jon Wolfe and Xiaobiao Xu and Rong Zhang",

note = "Publisher Copyright: {\textcopyright} 2026 Gokhan Danabasoglu et al.",

year = "2026",

month = jun,

day = "15",

doi = "10.5194/gmd-19-5071-2026",

language = "English",

volume = "19",

pages = "5071--5117",

journal = "Geoscientific Model Development",

issn = "1991-959X",

publisher = "Copernicus Publications",

number = "11",

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Danabasoglu, G , Castruccio, FS, Boza, B, Barthel, AM, Biastoch, A, Blaker, A, Bozec, A, Bruciaferri, D, Bryan, FO, Chassignet, EP, Fu, Y, Grooms, I, Guiavarc'h, C, Hayashida, H, Hogg, AMC, Holmes, RM, Iovino, D, Kiss, AE, Lozier, MS, Marques, G, Megann, A, Schwarzkopf, FU, Storkey, D, van Roekel, L, Wolfe, J, Xu, X & Zhang, R 2026, 'Simulated and observed transport estimates across the Overturning in the Subpolar North Atlantic Program (OSNAP) sections', Geoscientific Model Development, vol. 19, no. 11, pp. 5071-5117. https://doi.org/10.5194/gmd-19-5071-2026

TY - JOUR

T1 - Simulated and observed transport estimates across the Overturning in the Subpolar North Atlantic Program (OSNAP) sections

AU - Danabasoglu, Gokhan

AU - Castruccio, Frederic S.

AU - Boza, Burcu

AU - Barthel, Alice M.

AU - Biastoch, Arne

AU - Blaker, Adam

AU - Bozec, Alexandra

AU - Bruciaferri, Diego

AU - Bryan, Frank O.

AU - Chassignet, Eric P.

AU - Fu, Yao

AU - Grooms, Ian

AU - Guiavarc'h, Catherine

AU - Hayashida, Hakase

AU - Hogg, Andrew Mc C.

AU - Holmes, Ryan M.

AU - Iovino, Doroteaciro

AU - Kiss, Andrew E.

AU - Lozier, M. Susan

AU - Marques, Gustavo

AU - Megann, Alex

AU - Schwarzkopf, Franziska U.

AU - Storkey, Dave

AU - van Roekel, Luke

AU - Wolfe, Jon

AU - Xu, Xiaobiao

AU - Zhang, Rong

PY - 2026/6/15

Y1 - 2026/6/15

N2 - A comparison of simulated and observed overturning transports and related properties across the Overturning in the Subpolar North Atlantic Program (OSNAP) sections for the 2014–2022 period is presented, considering both depth and density space transports. The effort was motivated by the observational transport estimates at both OSNAP-West (OW) and OSNAP-East (OE) sections which show a minor role for the Labrador Sea (LS) in setting the mean and variability of the overturning in the subpolar North Atlantic. There are 9 participating groups from around the world, contributing a total of 18 ocean-sea-ice simulations with 6 different ocean models. The simulations use a common set of interannually varying atmospheric forcing datasets. The horizontal resolutions of the simulations range from nominal 1° to eddy-resolving resolutions of 0.1–0.05°. While there are many differences between the simulations and observations as well as among the individual simulations in terms of transport properties, the simulations show significantly larger transports at OE than at OW in agreement with the observations. Analyzing overturning circulations in both depth and density space together provides a more complete picture of the overturning properties and features. This analysis also reveals that, in both the simulations and observations, northward and southward flows substantially cancel each other at a given depth or density, producing much smaller residual (total) transports. Such cancellations tend to be much more prominent in depth space than in density space. In general, the observed transport features are captured better at OE than OW. The simulations generally show larger (smaller) transports with positive (negative) temperature and salinity biases in the upper ocean near the OSNAP sections, but with no such relationship with density biases. In high-resolution simulations, the transport profiles agree better with the observations, but challenges remain in some other metrics considered in our analysis. When transports are calculated using a density referenced to 2000 m depth, rather than the ocean surface, the relative contributions of transports at OW increase modestly.

AB - A comparison of simulated and observed overturning transports and related properties across the Overturning in the Subpolar North Atlantic Program (OSNAP) sections for the 2014–2022 period is presented, considering both depth and density space transports. The effort was motivated by the observational transport estimates at both OSNAP-West (OW) and OSNAP-East (OE) sections which show a minor role for the Labrador Sea (LS) in setting the mean and variability of the overturning in the subpolar North Atlantic. There are 9 participating groups from around the world, contributing a total of 18 ocean-sea-ice simulations with 6 different ocean models. The simulations use a common set of interannually varying atmospheric forcing datasets. The horizontal resolutions of the simulations range from nominal 1° to eddy-resolving resolutions of 0.1–0.05°. While there are many differences between the simulations and observations as well as among the individual simulations in terms of transport properties, the simulations show significantly larger transports at OE than at OW in agreement with the observations. Analyzing overturning circulations in both depth and density space together provides a more complete picture of the overturning properties and features. This analysis also reveals that, in both the simulations and observations, northward and southward flows substantially cancel each other at a given depth or density, producing much smaller residual (total) transports. Such cancellations tend to be much more prominent in depth space than in density space. In general, the observed transport features are captured better at OE than OW. The simulations generally show larger (smaller) transports with positive (negative) temperature and salinity biases in the upper ocean near the OSNAP sections, but with no such relationship with density biases. In high-resolution simulations, the transport profiles agree better with the observations, but challenges remain in some other metrics considered in our analysis. When transports are calculated using a density referenced to 2000 m depth, rather than the ocean surface, the relative contributions of transports at OW increase modestly.

KW - Multidecadal variability

KW - Impact

KW - Global ocean

KW - Southern-ocean

KW - Climate

KW - General-circulation model

KW - Sea-ice model

KW - Experimental protocols

KW - Part i

KW - Ocean model

UR - https://www.scopus.com/pages/publications/105042545281

U2 - 10.5194/gmd-19-5071-2026

DO - 10.5194/gmd-19-5071-2026

M3 - Article

AN - SCOPUS:105042545281

SN - 1991-959X

VL - 19

SP - 5071

EP - 5117

JO - Geoscientific Model Development

JF - Geoscientific Model Development

IS - 11

ER -

Simulated and observed transport estimates across the Overturning in the Subpolar North Atlantic Program (OSNAP) sections

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