Supporting Data for "Horizontal circulation across density surfaces contributes substantially to the long-term mean northern Atlantic Meridional Overturning Circulation"

This repository contains the key supporting data (in the netcdf format) for the following paper:

Zhang, R. and M. Thomas, 2021, Horizontal circulation across density surfaces contributes substantially to the long-term mean northern Atlantic Meridional Overturning Circulation,  Communications Earth & Environment, https://doi.org/10.1038/s43247-021-00182-y.

In this study, Robust Diagnostic Calculations (RDC) are conducted using a high-resolution global fully  coupled climate model, in which the ocean potential temperature and salinity are relaxed back to the observed long-term mean hydrographic data to provide a holistic picture of the long-term mean AMOC structure at northern high latitudes over the past several decades. For comparison, the high-resolution global coupled climate model used for the RDC experiments in this study is also employed to generate a present-day control simulation.

Descriptions of data files in this repository:

1. Mean sea surface height (SSH, in unit of m) from Robust Diagnostic Calculations (RDC) and the control simulation (MODEL), as shown in Fig. 2b,c in the paper. All are referenced to their own averages over the entire domain (80^oW-20^oE, 30^o-80^oN).

    RDC_SSH_30N80N_80w20E.nc

    MODEL_SSH_30N80N_80w20E.nc                    

2. Mean AMOC streamfunctions (Sv) across the OSNAP section, in density-space (potential density  \(\sigma_0, kg/m^3\) ) and depth-space (z, m) from RDC and MODEL, as shown in Fig. 3 in the paper.

OSNAP West:

RDC_moc_sigma0_OSNAP_West.nc

RDC_moc_z_OSNAP_West.nc

MODEL_moc_sigma0_OSNAP_West.nc

MODEL_moc_z_OSNAP_East.nc

OSNAP East:

RDC_moc_sigma0_OSNAP_East.nc

RDC_moc_z_OSNAP_East.nc

MODEL_moc_sigma0_OSNAP_East.nc

MODEL_moc_z_OSNAP_West.nc                      

Entire OSNAP section:

RDC_moc_sigma0_OSNAP_Total.nc

RDC_moc_z_OSNAP_Total.nc

MODEL_moc_sigma0_OSNAP_Total.nc

MODEL_moc_z_OSNAP_Total.nc          

3. Mean velocity (m/s) and potential density \((\sigma_0, kg/m^3)\) across the OSNAP section from RDC and MODEL, as shown in Fig. 4b,c in the paper.

RDC_velocity_OSNAP.nc

RDC_sigma0_OSNAP.nc

MODEL_velocity_OSNAP.nc

MODEL_sigma0_OSNAP.nc

4. Mean -z diagram of AMOC transport (Sv), i.e. integrated volume transport across OSNAP West and OSNAP East over each potential density \((\sigma_0, kg/m^3)\) bin and depth (z, m) bin, derived from OSNAP observations (OBS), RDC, and MODEL, as shown in Fig. 6 in the paper.

OBS_transport_sigma0-z_OSNAP_West.nc

OBS_transport_sigma0-z_OSNAP_East.nc         

RDC_transport_sigma0-z_OSNAP_West.nc

RDC_transport_sigma0-z_OSNAP_East.nc

MODEL_transport_sigma0-z_OSNAP_West.nc

MODEL_transport_sigma0-z_OSNAP_East.nc   

5. Mean AMOC streamfunctions (Sv) across Arctic-Atlantic gateways sections in density-space (potential density \(\sigma_0, kg/m^3\)) and depth-space (z, m) from RDC and MODEL, as shown in Fig. 7 in the paper.

Section across the Fram Strait and Barents Sea Opening:

RDC_moc_sigma0_FS_BSO.nc

RDC_moc_z_FS_BSO.nc

MODEL_moc_sigma0_FS_BSO.nc         

MODEL_moc_z_FS_BSO.nc       

Section across 68^oN in Nordic Seas:

RDC_moc_sigma0_NS_68N.nc

RDC_moc_z_NS_68N.nc

MODEL_moc_sigma0_NS_68N.nc          

MODEL_moc_z_NS_68N.nc       

Section across the Greenland-Scotland Ridge (GSR):

RDC_moc_sigma0_GSR.nc

RDC_moc_z_GSR.nc        

MODEL_moc_sigma0_GSR.nc

MODEL_moc_z_GSR.nc

6. Mean velocity (m/s) and potential density \((\sigma_0, kg/m^3)\) across Arctic-Atlantic gateways sections from RDC and MODEL, as shown in Fig. 8 in the paper.

Section across the Fram Strait and Barents Sea Opening:

RDC_velocity_FS_BSO.nc

RDC_sigma0_FS_BSO.nc

MODEL_velocity_FS_BSO.nc     

MODEL_sigma0_FS_BSO.nc      

Section across 68^oN in Nordic Seas:

RDC_velocity_NS_68N.nc

RDC_sigma0_NS_68N.nc

MODEL_velocity_NS_68N.nc                 

MODEL_sigma0_NS_68N.nc                              

Section across the Greenland-Scotland Ridge (GSR), also called the Greenland-Iceland-Scotland (GIS) Ridge:

RDC_velocity_GSR.nc

RDC_sigma0_GSR.nc

MODEL_velocity_GSR.nc

MODEL_sigma0_GSR.nc 

Acknowledgements We acknowledge the use of the following datasets and model code in this study: The World Ocean Atlas 2013 (WOA13) data were downloaded from the NOAA National Centers for Environmental Information (formerly the National Oceanographic Data) https://www.nodc.noaa.gov/cgi-bin/OC5/woa13/woa13.pl. The CSIRO ATLAS of REGIONAL SEAS 2009 version (CARS2009) data (http://www.marine.csiro.au/~dunn/cars2009/) were developed and provided by the Commonwealth Scientific and Industrial Research Organisation (CSIRO) Marine and Atmospheric Research, and downloaded from http://www.marine.csiro.au/atlas/. The climatological surface wind stress data are from the European Centre for Medium-range Weather Forecast (ECMWF): The ERA-Interim reanalysis data, Copernicus Climate Change Service (C3S) (accessed September 18, 2019), available from:

https://www.ecmwf.int/en/forecasts/datasets/archive-datasets/reanalysis-datasets/era-interim. The observed mean dynamic topography data were produced by CLS and distributed by Aviso+ with support from Cnes (https://www.aviso.altimetry.fr/), and downloaded from ftp://ftp-access.aviso.altimetry.fr/auxiliary/mdt/mdt_cnes_cls2013_global/. Data from the full OSNAP (Overturning in the Subpolar North Atlantic Program) array for the first 21 months (31-Jul-2014 to 20-Apr-2016) were downloaded from https://www.o-snap.org/. OSNAP data were collected and made freely available by the OSNAP project and all the national programs that contribute to it (www.o-snap.org). The code of the Geophysical Fluid Dynamics Laboratory (GFDL) coupled climate model version 2.5 (CM2.5) used in this study is publicly available at https://www.gfdl.noaa.gov/cm2-5-and-flor-quickstart/. The relevant citations for the above datasets and model code are listed in Zhang and Thomas, 2021.