Localized rapid warming of West Antarctic subsurface waters by remote winds

Spence, Paul; Holmes, R. M.; Hogg, Andrew McC.; Griffies, Stephen M.; Stewart, Kial Douglas; England, Matthew H.

doi:10.1038/nclimate3335

Cited by 108 publications

(132 citation statements)

References 44 publications

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“…Variations in sSO SSH associated with this mode correspond closely in space with anomalies in OSC of the same sign (Figures a and b), as expected from a quasi‐instantaneous oceanic response to changes in surface stress mediated by Ekman dynamics. The circumpolar coherence of SSH variations around the Antarctic continental shelf is indicative of the fast propagation of sea level fluctuations along the almost‐closed barotropic potential vorticity contours that encircle Antarctica, via topographic waves (Hughes et al, ; Kusahara & Ohshima, ; Spence et al, ). The mode of SSH variability characterized by MCA1 SSH,OSC has been documented with bottom pressure recorder and tide gauge data as well as numerical models and is often termed the “southern mode” (Aoki, ; Hughes et al, , ).…”

Section: Discussionmentioning

confidence: 99%

Phased Response of the Subpolar Southern Ocean to Changes in Circumpolar Winds

Garabato

Dotto

Hooley

et al. 2019

Geophysical Research Letters

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The response of the subpolar Southern Ocean (sSO) to wind forcing is assessed using satellite radar altimetry. sSO sea level exhibits a phased, zonally coherent, bimodal adjustment to circumpolar wind changes, involving comparable seasonal and interannual variations. The adjustment is effected via a quasi‐instantaneous exchange of mass between the Antarctic continental shelf and the sSO to the north, and a 2‐month‐delayed transfer of mass between the wider Southern Ocean and the subtropics. Both adjustment modes are consistent with an Ekman‐mediated response to variations in surface stress. Only the fast mode projects significantly onto the surface geostrophic flow of the sSO; thus, the regional circulation varies in phase with the leading edge of sSO sea level variability. The surface forcing of changes in the sSO system is partly associated with variations of surface winds linked to the Southern Annular Mode and is modulated by sea ice cover near Antarctica.

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Section: Discussionmentioning

confidence: 99%

Phased Response of the Subpolar Southern Ocean to Changes in Circumpolar Winds

Garabato

Dotto

Hooley

et al. 2019

Geophysical Research Letters

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“…Observations and models show large variability of DSW and ALBW properties prior to calving (Figure ; e.g., Cougnon et al, ; Kusahara et al, ; Lacarra et al, ; Shadwick et al, ; van Wijk & Rintoul, ; Williams et al, ). While these studies suggest that variations in sea ice production can explain much of the variability, other processes also likely contribute, including wind‐driven changes in circulation (e.g., Spence et al, ), changes in freshwater input (e.g., Aoki et al, ), variability in cross‐shelf exchange, changes in entrainment (and stratification, e.g., Shimada et al, ), and conditioning by summer stratification (Marsland et al, ). A combination of these factors may explain the relatively fresh DSW present on the shelf in January 2001 (Shadwick et al, ; Williams et al, ) and the particularly cold, dense, and thick layer of ALBW observed in 2002.…”

Section: Discussionmentioning

confidence: 99%

Change in Dense Shelf Water and Adélie Land Bottom Water Precipitated by Iceberg Calving

Snow

Rintoul

Sloyan

et al. 2018

Geophysical Research Letters

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Antarctic Bottom Water supplies the deep limb of the global overturning circulation and ventilates the abyssal ocean. Antarctic Bottom Water has warmed, freshened, and contracted in recent decades, but the causes remain poorly understood. We use unique multiyear observations from the continental shelf and deep ocean near the Mertz Polynya to examine the sensitivity of this bottom water formation region to changes on the continental shelf, including the calving of a large iceberg. Postcalving, the seasonal cycle of Dense Shelf Water (DSW) density almost halved in amplitude and the volume of DSW available for export reduced. In the deep ocean, the density and volume of Adélie Land Bottom Water decreased sharply after calving, while oxygen concentrations remained high, indicating continued ventilation by DSW. This natural experiment illustrates how local changes in forcing over the Antarctic continental shelf can drive large and rapid changes in the abyssal ocean.

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“…Still,

\overset{Φ^{eddy}}{true}

has its maximum correlation with

\overset{EKE}{true}

at 5‐month lag ( r = 0.46, significant at α = 99.9%). Perhaps the local uplifting of isotherms associated with the arrival of remotely generated fast barotropic Kelvin waves (Spence et al, ) and/or slower continental shelf wave modes (Kusahara & Ohshima, ) can help explain this nonintuitive result. However, these processes are not identifiable in the present circumpolarly integrated, monthly averaged analysis.…”

Section: The Cross‐shelf Break Heat Transport Along the Antarctic Conmentioning

confidence: 99%

“…In West Antarctica, episodic warm intrusions found in global simulations have been connected to the arrival of fast, barotropic Kelvin waves originating from wind perturbations in East Antarctica (Spence et al, ). Our findings suggest that a similar mechanism may be operating in POP: monthly time scale changes in the zonal wind along East Antarctica (exemplified by the localized seasonal patches in Figure ) serve as an ancillary mechanism for warm intrusions along the shelf edge in West Antarctica.…”

Section: The Cross‐shelf Break Heat Transport Along the Antarctic Conmentioning

confidence: 99%

Oceanic Heat Delivery to the Antarctic Continental Shelf: Large‐Scale, Low‐Frequency Variability

2018

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Onshore penetration of oceanic water across the Antarctic continental slope (ACS) plays a major role in global sea level rise by delivering heat to the Antarctic marginal seas, thus contributing to the basal melting of ice shelves. Here the time‐mean (Φmean) and eddy (Φeddy) components of the heat transport (Φ) across the 1,000‐m isobath along the entire ACS are investigated using a 0.1∘ global coupled ocean/sea ice simulation based on the Los Alamos Parallel Ocean Program (POP) and sea ice (Community Ice CodE) models. Comparison with in situ hydrography shows that the model successfully represents the basic water mass structure, with a warm bias in the Circumpolar Deep Water layer. Segments of on‐shelf Φ, with lengths of O(100–1,000 km), are found along the ACS. The circumpolar integral of the annually averaged Φ is O(20 TW), with Φeddy always on‐shelf, while Φmean fluctuates between on‐shelf and off‐shelf. Stirring along isoneutral surfaces is often the dominant process by which eddies transport heat across the ACS, but advection of heat by both mean flow‐topography interactions and eddies can also be significant depending on the along‐ and across‐slope location. The seasonal and interannual variability of the circumpolarly integrated Φmean is controlled by convergence of Ekman transport within the ACS. Prominent warming features at the bottom of the continental shelf (consistent with observed temperature trends) are found both during high‐Southern Annular Mode and high‐Niño 3.4 periods, suggesting that climate modes can modulate the heat transfer from the Southern Ocean to the ACS across the entire Antarctic margin.

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Localized rapid warming of West Antarctic subsurface waters by remote winds

Cited by 108 publications

References 44 publications

Phased Response of the Subpolar Southern Ocean to Changes in Circumpolar Winds

Phased Response of the Subpolar Southern Ocean to Changes in Circumpolar Winds

Change in Dense Shelf Water and Adélie Land Bottom Water Precipitated by Iceberg Calving

Oceanic Heat Delivery to the Antarctic Continental Shelf: Large‐Scale, Low‐Frequency Variability

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