Response of Southern Hemisphere western boundary current regions to future zonally symmetric and asymmetric atmospheric changes

Goyal, Rishav; England, Matthew H.; Jucker, Martin; SenGupta, Alex

doi:10.1002/essoar.10507696.1

Cited by 2 publications

(2 citation statements)

References 49 publications

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“…Here, the local conditions (e.g., nutrient concentrations) are important. Nevertheless, the impact on boundary current transports and Chl‐a might be more nuanced due to the asymmetry of wind trends over the Southern Ocean (Beal & Elipot, 2016; Goyal et al., 2021; Noh et al., 2021; Sallée et al., 2010; Waugh et al., 2020), which results in regional variations. Here more regional and atmospheric coupled studies are needed to understand the local response.…”

Section: Conclusion and Discussionmentioning

confidence: 99%

The Response of the Subtropical Front to Changes in the Southern Hemisphere Westerly Winds—Evidence From Models and Observations

Behrens

Bostock

2023

JGR Oceans

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The location of the Subtropical Front (STF), the boundary between Subtropical and Subantarctic Water in the Southern Ocean is proposed to be influenced by the strength and location of the Southern Hemisphere westerly winds. We use a hydrodynamic hindcast model and recent observations to test if changes in the westerly winds can cause meridional shifts in the STF over interannual to decadal timescales by modulating local Ekman transport. We find that increased, or northward, shifted westerly winds lead to an enhanced northward Ekman transport over large parts of the Southern Ocean, resulting in a northward shift in the STF. Conversely for weaker or southward shifted westerly winds where the STF migrates south. However, this relationship breaks down in regions with strong eddy variability and western boundary current systems. In these regions an increase in westerly winds lead to a southward shift in the STF. Observation data from 2004 to 2019 display a southward shift of STF associated with the positive Southern Annular Mode. However, the shift is smaller than the latitudinal shifts in the location of the zero wind stress curl and maximum westerly winds (−0.4° latitude/decade). This discrepancy is due to positive Ekman trends resulting from the intensification of the westerly winds, which oppose the southward migration. Changes in the Ekman transport and the overall southward shift of the STF have also resulted in an observed positive trend in chlorophyll‐a concentrations south of the STF, which could have ramifications for marine ecosystems and the biological pump in the Southern Ocean.

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Section: Conclusion and Discussionmentioning

confidence: 99%

The Response of the Subtropical Front to Changes in the Southern Hemisphere Westerly Winds—Evidence From Models and Observations

Behrens

Bostock

2023

JGR Oceans

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“…ACCESS‐CM2 data used to force the ocean model simulations can be downloaded from the Earth System Grid Federation (ESGF) ‐ https://esgf-node.llnl.gov/search/cmip6/. Data from the ocean model simulations required to reproduce the results presented in this study has been made available and can be freely downloaded from Goyal, England, et al., 2021 https://data.mendeley.com/datasets/7sw7kf8nxk/draft?a=b9062eee-4582-4187-948d-cbd194901206.…”

Section: Data Availability Statementmentioning

confidence: 99%

Response of Southern Hemisphere Western Boundary Current Regions to Future Zonally Symmetric and Asymmetric Atmospheric Changes

et al. 2021

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Subtropical western boundary currents (WBCs) are often associated with hotspots of global warming, with certain WBC extension regions warming 3–4 times faster than the global mean. In the Southern Hemisphere, strong warming over the WBC extensions has been observed over the last few decades, with enhanced warming projected into the future. This amplified warming has primarily been linked to poleward intensification of the mid‐latitude westerly winds in the Southern Hemisphere. Changes in these winds are often thought of as being zonally symmetric; however, recent studies show that they contain strong zonal asymmetries in certain ocean basins. The importance of these zonal asymmetries for the Southern Ocean has not yet been investigated. In this study, we use an ocean‐sea‐ice model forced by prescribed atmospheric fields to quantify the contribution of projected zonally asymmetric atmospheric changes in generating future ocean warming and circulation changes in the subtropical WBC regions. We find that the zonally asymmetric component of atmospheric forcing, characterized by a pattern that is consistent across CMIP6 models, can explain more than 30% (>2°C) of the sea surface temperature (SST) warming found in the Tasman Sea and southern Australia region and a sizable fraction of warming in the Agulhas Current region. These changes in SST in both the Indian and Pacific basins are found to be primarily driven by increases in the advection of warm tropical water to the mid‐latitudes due to changes in the large‐scale subtropical ocean gyres, which in turn can largely be explained by changes in the mid‐latitude surface wind stress patterns.

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Response of Southern Hemisphere western boundary current regions to future zonally symmetric and asymmetric atmospheric changes

Cited by 2 publications

References 49 publications

The Response of the Subtropical Front to Changes in the Southern Hemisphere Westerly Winds—Evidence From Models and Observations

The Response of the Subtropical Front to Changes in the Southern Hemisphere Westerly Winds—Evidence From Models and Observations

Response of Southern Hemisphere Western Boundary Current Regions to Future Zonally Symmetric and Asymmetric Atmospheric Changes

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