DOI: 10.5281/zenodo.13370393
title: Supporting data for: "Weakening of the AMOC and Strengthening of Labrador Sea Deep Convection in Response to External Freshwater Forcing"

description: This repository contains the key supporting data (in the netcdf format) for the following paper:Wei, X. and R. Zhang, 2024, Weakening of the AMOC and Strengthening of Labrador Sea Deep Convection in Response to External Freshwater Forcing, Nature Communications.

In this study, control and water hosing ensembles are conducted using a coupled climate model (GFDL CM4) with an eddy-permitting ocean component. The anomaly is defined as the difference between the water hosing and control ensembles (anomaly = water hosing - control). This paper investigates mechanisms of the AMOC weakening and its subsequent impact on the Labrador Sea open-ocean deep convection in response to external freshwater forcing.

Descriptions of data files in this repository:

Main figures:

1. The anomalies of the OSNAP AMOC and the Labrador Sea March mixed layer depth (MLD), as shown in Fig. 1 in the paper. 

The anomalies of the maximum AMOC and the AMOC at a relatively dense level around sigma0=27.84 kg/m3 across the entire OSNAP section in density space:

Anomaly_AMOC_max_OSNAP.nc

Anomaly_AMOC_denser_OSNAP.nc

The anomalies of the maximum AMOC across OSNAP West and OSANP East in density space:

Anomaly_AMOC_max_OSNAP_WEST.nc

Anomaly_AMOC_max_OSNAP_EAST.nc

The March mixed layer depth (MLD) in the Labrador Sea:

Anomaly_MLD_003_March_Labrador.nc

The spatial map of March MLD climatology and anomaly:

Control_MLD_003_March_spatial.nc

Anomaly_MLD_003_March_spatial.nc

2. The climatological mean (from the control and water hosing ensembles) and anomalies of the AMOC streamfunction across the OSNAP section, in density-space and depth-space, as shown in Fig. 2 in the paper.

OSNAP West:

Control_moc_sigma0_OSNAP_WEST.nc

Control_moc_z_OSNAP_WEST.nc

WaterHosing_moc_sigma0_OSNAP_WEST.nc

WaterHosing_moc_z_OSNAP_WEST.nc

Anomaly_moc_sigma0_OSNAP_WEST.nc

Anomaly_moc_z_OSNAP_WEST.nc

OSNAP East:

Control_moc_sigma0_OSNAP_EAST.nc

Control_moc_z_OSNAP_EAST.nc

WaterHosing_moc_sigma0_OSNAP_EAST.nc

WaterHosing_moc_z_OSNAP_EAST.nc

Anomaly_moc_sigma0_OSNAP_EAST.nc

Anomaly_moc_z_OSNAP_EAST.nc

Entire OSNAP section:

Control_moc_sigma0_OSNAP.nc

Control_moc_z_OSNAP.nc

WaterHosing_moc_sigma0_OSNAP.nc

WaterHosing_moc_z_OSNAP.nc

Anomaly_moc_sigma0_OSNAP.nc

Anomaly_moc_z_OSNAP.nc

3. The climatological mean (from the control ensemble) and anomalies of salinity, potential temperature, and potential density across the OSNAP section, as shown in Fig. 3 in the paper.

Control_salinity_OSNAP.nc

Control_temperature_OSNAP.nc

Control_sigma0_OSNAP.nc

Anomaly_salinity_OSNAP.nc

Anomaly_temperature_OSNAP.nc

Anomaly_sigma0_OSNAP.nc

4. The sigma-z diagram of climatological mean (from the control and water hosing ensembles) and anomalies of the AMOC transport across OSNAP East, i.e. integrated volume transport across OSNAP East over each potential density bin and depth bin, as shown in Fig. 4 in the paper.

Control_SigmaZ_OSNAP_EAST.nc

WaterHosing_SigmaZ_OSNAP_EAST.nc

Anomaly_SigmaZ_OSNAP_EAST.nc

5.The deep ocean potential density anomalies along with its thermal and haline components over the west boundary and eastern regions of the OSNAP East subsection, and the AMOC anomalies at a relatively dense level around sigma0=27.84 kg/m3 across OSNAP East in density space, as shown in Fig. 5 in the paper.

Anomaly_sigma_west.nc

Anomaly_sigmaS_west.nc

Anomaly_sigmaT_west.nc

Anomaly_sigma_east.nc

Anomaly_sigmaS_east.nc

Anomaly_sigmaT_east.nc

Anomaly_sigma_diff.nc

Anomaly_sigmaS_diff.nc

Anomaly_sigmaT_diff.nc

Anomaly_AMOC_denser_OSANP_EAST.nc

6.The transient salt-based FWF anomalies, dye-based FWF anomalies and their difference at the upper ocean (413m), as shown in Fig. 6 in the paper, and at the deep ocean (2250m), as shown in Fig. 7 in the paper.

Anomaly_FWF_salt_413m_10yr.nc

Anomaly_FWF_dye_413m_10yr.nc

Anomaly_FWF_diff_413m_10yr.nc

Anomaly_FWF_salt_413m_20yr.nc

Anomaly_FWF_dye_413m_20yr.nc

Anomaly_FWF_diff_413m_20yr.nc

Anomaly_FWF_salt_413m_30yr.nc

Anomaly_FWF_dye_413m_30yr.nc

Anomaly_FWF_diff_413m_30yr.nc

Anomaly_FWF_salt_413m_40yr.nc

Anomaly_FWF_dye_413m_40yr.nc

Anomaly_FWF_diff_413m_40yr.nc

Anomaly_FWF_salt_413m_50yr.nc

Anomaly_FWF_dye_413m_50yr.nc

Anomaly_FWF_diff_413m_50yr.nc

Anomaly_FWF_salt_2250m_10yr.nc

Anomaly_FWF_dye_2250m_10yr.nc

Anomaly_FWF_diff_2250m_10yr.nc

Anomaly_FWF_salt_2250m_20yr.nc

Anomaly_FWF_dye_2250m_20yr.nc

Anomaly_FWF_diff_2250m_20yr.nc

Anomaly_FWF_salt_2250m_30yr.nc

Anomaly_FWF_dye_2250m_30yr.nc

Anomaly_FWF_diff_2250m_30yr.nc

Anomaly_FWF_salt_2250m_40yr.nc

Anomaly_FWF_dye_2250m_40yr.nc

Anomaly_FWF_diff_2250m_40yr.nc

Anomaly_FWF_salt_2250m_50yr.nc

Anomaly_FWF_dye_2250m_50yr.nc

Anomaly_FWF_diff_2250m_50yr.nc

7.Climatological mean (from the control ensemble) and anomalies of salinity, potential temperature, potential density and zonal velocity along the Iceland-Scotland Overflow pathway, as shown in Fig. 8 in the paper.

Control_salinity_ISOW.nc

Control_temperature_ISOW.nc

Control_sigma_ISOW.nc

Control_u_ISOW.nc

Anomaly_salinity_ISOW.nc

Anomaly_temperature_ISOW.nc

Anomaly_sigma_ISOW.nc

Anomaly_u_ISOW.nc

8.The salt-based FWF anomalies, dye-based FWF anomalies and their difference across the Iceland-Scotland Overflow section, as shown in Fig. 9 in the paper.

Anomaly_FWF_salt_ISOW.nc

Anomaly_FWF_dye_ISOW.nc

Anomaly_FWF_diff_ISOW.nc

Supplementary figures:

S1. The anomalies of the density-space AMOC streamfunction as shown in Supplementary Fig. 1 in the paper.

SuppFig1.nc

S2. The extra-tropical North Atlantic subsurface (413m) temperature anomalies as shown in Supplementary Fig. 2 in the paper.

SuppFig2.nc

S3. The climatological mean (from the control and water hosing ensembles) and anomalies of the AMOC streamfunction, surface forced water mass transformation (WMTS) and interior mixing forced water mass transformation (WMTM), as shown in Supplementary Fig. 3 in the paper.

SuppFig3_streamfunction.nc

SuppFig3_surfaceWMT.nc

SuppFig3_interiorWMT.nc

SuppFig3_mask_section.nc

S4. The climatological mean of the velocity across the OSNAP section in the control ensemble, as shown in Supplementary Fig. 4 in the paper.

SuppFig4.nc

S5. The transient salinity anomalies, potential temperature anomalies and potential density anomalies across the OSNAP section, as shown in Supplementary Fig. 5 in the paper.

SuppFig5_11_20yr.nc

SuppFig5_21_30yr.nc

SuppFig5_31_40yr.nc

SuppFig5_41_50yr.nc

S6. The transient salt-based FWF anomalies, dye-based FWF anomalies and their difference at 625m, as shown in Supplementary Fig. 6 in the paper.

SuppFig6_10yr.nc

SuppFig6_20yr.nc

SuppFig6_30yr.nc

SuppFig6_40yr.nc

SuppFig6_50yr.nc

S7. The salt-based FWF anomalies, dye-based FWF anomalies and their difference across the OSNAP section, as shown in Supplementary Fig. 7 in the paper.

SuppFig7.nc

S8. The anomalies of March Labrador Sea mixed layer depth (MLD), vertical potential density difference, surface and deep ocean potential density, as shown in Supplementary Fig. 8 in the paper.

SuppFig8.nc

S9. The climatological mean salinity difference between the ISOW-associated NEADW layer and the core Labrador Sea Water layer, and the inverse horizontal grid resolution of GFDL CM4 (this study) and CMIP6 models as shown in Supplementary Fig. 9 in the paper. The CMIP6 model data were downloaded from https://aims2.llnl.gov/search/cmip6/.

The climatological mean salinity difference between the ISOW-associated NEADW layer and the core Labrador Sea Water layer in WOA18 as shown in Supplementary Fig. 9 in the paper. The WOA18 data were downloaded from the NOAA National Centers for Environmental Information (formerly the National Oceanographic Data) https://www.ncei.noaa.gov/products/world-ocean-atlas/.

SuppFig9.nc

S10. The supplementary Fig. 10 shares the same data of climatological mean of the AMOC streamfunction across the OSNAP section in density-space in the control ensemble with Figure 2 in the paper. The OSNAP observation data were downloaded from www.o-snap.org.

Control_moc_sigma0_OSNAP_WEST.nc

Control_moc_sigma0_OSNAP_EAST.nc

Control_moc_sigma0_OSNAP.nc

Acknowledgments

We acknowledge the use of the following datasets and model code in this study: The World Ocean Atlas 2018 (WOA18) data were downloaded from the NOAA National Centers for Environmental Information (formerly the National Oceanographic Data) https://www.ncei.noaa.gov/products/world-ocean-atlas/. The Data from the OSNAP (Overturning in the Subpolar North Atlantic Program) array 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 CMIP6 (Coupled Model Intercomparison Project Phase 6) model data were downloaded from https://aims2.llnl.gov/search/cmip6/. The source code of the Geophysical Fluid Dynamics Laboratory (GFDL) coupled climate model version 4 (CM4) is publicly available at https://doi.org/10.5281/zenodo.3339397. The surface forced water mass transformation (WMTS) is calculated using the source code developed by Drake et al. 2024 at https://github.com/hdrake/xwmt. The relevant citations for the above datasets and model code are listed in Wei and Zhang 2024.