Kelvin Waves around Antarctica

Kusahara, Kazuya; Ohshima, Κay I.

doi:10.1175/jpo-d-14-0051.1

Cited by 18 publications

(14 citation statements)

References 20 publications

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“…TRWs may directly contribute to the steering of CDW onto warm continental shelves via troughs (St‐Laurent et al, ), but their importance relative to, for example, tides and coherent eddies (Couto et al, ; Wang et al, ), remains unknown. CTWs are generated by circum‐Antarctic and remote atmospheric variability (Kusahara & Ohshima, ), and the former has recently been identified as a mechanism of rapidly generating heat content anomalies along the WAP (Spence et al, ).…”

Section: Dynamics and Variability Of The Ascmentioning

confidence: 99%

The Antarctic Slope Current in a Changing Climate

Thompson

Stewart

Spence

et al. 2018

Reviews of Geophysics

271

330

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The Antarctic Slope Current (ASC) is a coherent circulation feature that rings the Antarctic continental shelf and regulates the flow of water toward the Antarctic coastline. The structure and variability of the ASC influences key processes near the Antarctic coastline that have global implications, such as the melting of Antarctic ice shelves and water mass formation that determines the strength of the global overturning circulation. Recent theoretical, modeling, and observational advances have revealed new dynamical properties of the ASC, making it timely to review. Earlier reviews of the ASC focused largely on local classifications of water properties of the ASC's primary front. Here we instead provide a classification of the current's frontal structure based on the dynamical mechanisms that govern both the along‐slope and cross‐slope circulation; these two modes of circulation are strongly coupled, similar to the Antarctic Circumpolar Current. Highly variable motions, such as dense overflows, tides, and eddies are shown to be critical components of cross‐slope and cross‐shelf exchange, but understanding of how the distribution and intensity of these processes will evolve in a changing climate remains poor due to observational and modeling limitations. Results linking the ASC to larger modes of climate variability, such as El Niño, show that the ASC is an integral part of global climate. An improved dynamical understanding of the ASC is still needed to accurately model and predict future Antarctic sea ice extent, the stability of the Antarctic ice sheets, and the Southern Ocean's contribution to the global carbon cycle.

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Section: Dynamics and Variability Of The Ascmentioning

confidence: 99%

The Antarctic Slope Current in a Changing Climate

Thompson

Stewart

Spence

et al. 2018

Reviews of Geophysics

271

330

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“…As emphasized in section 2d, our ''eddy'' and ''tidal'' components only approximately correspond to their representative flow phenomena, and include other flows that evolve on comparable time scales. For example, the effect of tides could be more accurately isolated via tidal harmonic analysis (Foreman and Henry 1989) and the ''eddy'' component may also include phenomena such as lowfrequency coastal-trapped waves (Kusahara and Ohshima 2014;Spence et al 2017) and the oceanic response to synoptic wind variability (e.g., Davis et al 2018). Our analysis options were strongly constrained by the computational cost of performing operations on the very large volume of model output (see Stewart et al 2018), a problem that might be ameliorated in future by improved computational infrastructure and tools for working with large datasets.…”

Section: Fig A2 As Inmentioning

confidence: 99%

Acceleration and Overturning of the Antarctic Slope Current by Winds, Eddies, and Tides

Stewart

Klocker

Menemenlis

2019

Journal of Physical Oceanography

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All exchanges between the open ocean and the Antarctic continental shelf must cross the Antarctic Slope Current (ASC). Previous studies indicate that these exchanges are strongly influenced by mesoscale and tidal variability, yet the mechanisms responsible for setting the ASC’s transport and structure have received relatively little attention. In this study the roles of winds, eddies, and tides in accelerating the ASC are investigated using a global ocean–sea ice simulation with very high resolution (1/48° grid spacing). It is found that the circulation along the continental slope is accelerated both by surface stresses, ultimately sourced from the easterly winds, and by mesoscale eddy vorticity fluxes. At the continental shelf break, the ASC exhibits a narrow (~30–50 km), swift (>0.2 m s−1) jet, consistent with in situ observations. In this jet the surface stress is substantially reduced, and may even vanish or be directed eastward, because the ocean surface speed matches or exceeds that of the sea ice. The shelfbreak jet is shown to be accelerated by tidal momentum advection, consistent with the phenomenon of tidal rectification. Consequently, the shoreward Ekman transport vanishes and thus the mean overturning circulation that steepens the Antarctic Slope Front (ASF) is primarily due to tidal acceleration. These findings imply that the circulation and mean overturning of the ASC are not only determined by near-Antarctic winds, but also depend crucially on sea ice cover, regionally-dependent mesoscale eddy activity over the continental slope, and the amplitude of tidal flows across the continental shelf break.

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“…Only longer period, longer wavelength gravity waves, that have sufficient energy below the base of the ice shelf to enter the ice shelf cavity, can couple into flexural-gravity waves. Other ice shelf ''plate waves'' Journal of Geophysical Research: Oceans 10.1002/2017JC012913 excited by ocean gravity wave interactions include flexural (asymmetric) and extensional (symmetric) Lamb waves [Lamb, 1917;Press and Ewing, 1951;Graff, 1975]. Flexural Lamb waves have dominant vertical motions, while extensional Lamb waves have dominant horizontal motions.…”

Section: Water-ice-coupled Flexural-gravity Wave Propagation Charactementioning

confidence: 99%

“…The collapse and disintegration of Antarctic Peninsula ice shelves over the past three decades has been attributed to hydrofracturing [Scambos et al, 2009;Banwell et al, 2013] and buoyancy-induced bending stresses [Braun et al, 2009;Scambos et al, 2009], with ice shelf thinning from basal melting contributing to weakening and fracturing. These factors will be exacerbated by rising ocean and atmosphere temperatures, which will have a negative impact on ice shelf stability [Joughin and Alley, 2011].…”

Section: Introductionmentioning

confidence: 99%

Tsunami and infragravity waves impacting Antarctic ice shelves

et al. 2017

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The responses of the Ross Ice Shelf (RIS) to the 16 September 2015 8.3 (Mw) Chilean earthquake tsunami (>75 s period) and to oceanic infragravity (IG) waves (50–300 s period) were recorded by a broadband seismic array deployed on the RIS from November 2014 to November 2016. Here we show that tsunami and IG‐generated signals within the RIS propagate at gravity wave speeds (∼70 m/s) as water‐ice coupled flexural‐gravity waves. IG band signals show measureable attenuation away from the shelf front. The response of the RIS to Chilean tsunami arrivals is compared with modeled tsunami forcing to assess ice shelf flexural‐gravity wave excitation by very long period (VLP; >300 s) gravity waves. Displacements across the RIS are affected by gravity wave incident direction, bathymetry under and north of the shelf, and water layer and ice shelf thicknesses. Horizontal displacements are typically about 10 times larger than vertical displacements, producing dynamical extensional motions that may facilitate expansion of existing fractures. VLP excitation is continuously observed throughout the year, with horizontal displacements highest during the austral winter with amplitudes exceeding 20 cm. Because VLP flexural‐gravity waves exhibit no discernable attenuation, this energy must propagate to the grounding zone. Both IG and VLP band flexural‐gravity waves excite mechanical perturbations of the RIS that likely promote tabular iceberg calving, consequently affecting ice shelf evolution. Understanding these ocean‐excited mechanical interactions is important to determine their effect on ice shelf stability to reduce uncertainty in the magnitude and rate of global sea level rise.

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Kelvin Waves around Antarctica

Cited by 18 publications

References 20 publications

The Antarctic Slope Current in a Changing Climate

The Antarctic Slope Current in a Changing Climate

Acceleration and Overturning of the Antarctic Slope Current by Winds, Eddies, and Tides

Tsunami and infragravity waves impacting Antarctic ice shelves

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