The Amundsen Sea and the Antarctic Ice Sheet

Jacobs, Stanley S.; Jenkins, Adrian; Hellmer, Hartmut; Giulivi, Claudia F.; Nitsche, F. O.; Huber, Bruce A.; Guerrero, Ricardo

doi:10.5670/oceanog.2012.90

Cited by 137 publications

(165 citation statements)

References 34 publications

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“…S1) and yields a different spatial pattern with higher peak melt (187 m yr −1 ). Irrespective of correction for this dynamic component, these estimates are 1-5-year snapshots of melt at single points, and the interannual variability in melt rates in the region (e.g., Dutrieux et al, 2014;Jacobs et al, 2012) prevents extrapolation through time. Average melt rates beneath the shelves cannot be easily obtained from these point measurements, but the polygon-based methods we use, though limited in spatial resolution, yield average rates beneath large portions of the shelves.…”

Section: Comparison To Previous Melt Estimatesmentioning

confidence: 99%

Changes in flow of Crosson and Dotson ice shelves, West Antarctica, in response to elevated melt

et al. 2018

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Abstract. Crosson and Dotson ice shelves are two of the most rapidly changing outlets in West Antarctica, displaying both significant thinning and grounding-line retreat in recent decades. We used remotely sensed measurements of velocity and ice geometry to investigate the processes controlling their changes in speed and grounding-line position over the past 20 years. We combined these observations with inverse modeling of the viscosity of the ice shelves to understand how weakening of the shelves affected this speedup. These ice shelves have lost mass continuously since the 1990s, and we find that this loss results from increasing melt beneath both shelves and the increasing speed of Crosson. High melt rates persisted over the period covered by our observations (1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014), with the highest rates beneath areas that ungrounded during this time. Grounding-line flux exceeded basin-wide accumulation by about a factor of 2 throughout the study period, consistent with earlier studies, resulting in significant loss of grounded as well as floating ice. The near doubling of Crosson's speed in some areas during this time is likely the result of weakening of its margins and retreat of its grounding line. This speedup contrasts with Dotson, which has maintained its speed despite increasingly high melt rates near its grounding line, likely a result of the sustained competency of the shelf. Our results indicate that changes to melt rates began before 1996 and suggest that observed increases in melt in the 2000s compounded an ongoing retreat of this system. Advection of a channel along Dotson, as well as the grounding-line position of Kohler Glacier, suggests that Dotson experienced a change in flow around the 1970s, which may be the initial cause of its continuing retreat.

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Section: Comparison To Previous Melt Estimatesmentioning

confidence: 99%

Changes in flow of Crosson and Dotson ice shelves, West Antarctica, in response to elevated melt

et al. 2018

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“…The smaller ice shelves in the Amundsen Sea are melted by warmer waters. Sea ice growth is less intense in the Amundsen Sea (Petty et al 2013), allowing warm and saline Circumpolar Deep Water at approximately 18C to flood the continental shelf and occupy its ice shelf cavities (Jacobs et al 2012). These ice shelves melt at mean rates of O(10) m yr 21 and hence are much smaller than FRIS, responding to ocean changes on a time scale of only a few months (Heimbach and Losch 2012).…”

Section: Introductionmentioning

confidence: 99%

The Transient Response of Ice Shelf Melting to Ocean Change

Holland

2017

Journal of Physical Oceanography

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Idealized modeling studies have shown that the melting of ice shelves varies as a quadratic function of ocean temperature. However, this result is the equilibrium response, derived from steady ice-ocean simulations subjected to a fixed ocean forcing. This study considers instead the transient response of melting, using unsteady simulations subjected to forcing conditions that are oscillated with a range of periods. The results show that the residence time of water in the subice cavity offers a critical time scale. When the forcing varies slowly (period of oscillation residence time), the cavity is fully flushed with forcing anomalies at all stages of the cycle and melting follows the equilibrium response. When the forcing varies rapidly (period # residence time), multiple cold and warm anomalies coexist in the cavity, cancelling each other in the spatial mean and thus inducing a relatively steady melt rate. This implies that all ice shelves have a maximum frequency of ocean variability that can be manifested in melting. Between these two extremes, an intermediate regime occurs in which melting follows the equilibrium response during the cooling phase of the forcing cycle, but deviates during warming. The results show that ice shelves forced by warm water have high melt rates, high equilibrium sensitivity, and short residence times and hence a short time scale over which the equilibrium sensitivity is manifest. The most rapid melting adjustment is induced by warm anomalies that are also saline. Thus, ice shelves in the Amundsen and Bellingshausen Seas, Antarctica, are highly sensitive to ocean change.

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“…The main reason for their decline appears to be flow of warm dense water onto the shelf, channeled by bathymetric troughs leading to the deep inner basins. This has been observed on the Marguerite Trough [5][6][7] and on the Amundsen Shelf [8][9][10]. Model studies [11,12] indicate that the on-shelf flow of warm dense water is forced by along-shelf (i.e., eastward in the Amundsen Sea) winds.…”

Section: Introductionmentioning

confidence: 90%

Correlation between Synthetic Aperture Radar Surface Winds and Deep Water Velocity in the Amundsen Sea, Antarctica

et al. 2013

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Abstract:The recent observed thinning of the glacier ice shelves in the Amundsen Sea (Antarctica) has been attributed to warm deep currents, possibly induced by along-coast winds in the vicinity of the glacial ice sheet. Here, high resolution maps of wind fields derived from Synthetic Aperture Radar (SAR) data have been studied and correlated with subsurface measurements of the deep water velocities in the Amundsen Sea area. Focus is on periods with low ice coverage in 2010 and 2011. In 2010, which had comparatively low ice coverage, the results indicate a more rapid response to wind forcing in the deep currents than in 2011. The SAR wind speed maps have better spatial resolution than available reanalysis data, and higher maximum correlation was obtained with SAR data than with reanalysis data despite the lower temporal resolution. The maximum correlation was R = 0.71, in a direction that is consistent with wind-driven Ekman theory. This is significantly larger than in previous studies. The larger correlation could be due to the better spatial resolution or the restriction to months with minimum ice coverage. The results indicate that SAR is a useful complement to infer the subsurface variability of the ocean circulation in remote areas in polar oceans. OPEN ACCESSRemote Sens. 2013, 5 4089

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The Amundsen Sea and the Antarctic Ice Sheet

Cited by 137 publications

References 34 publications

Changes in flow of Crosson and Dotson ice shelves, West Antarctica, in response to elevated melt

Changes in flow of Crosson and Dotson ice shelves, West Antarctica, in response to elevated melt

The Transient Response of Ice Shelf Melting to Ocean Change

Correlation between Synthetic Aperture Radar Surface Winds and Deep Water Velocity in the Amundsen Sea, Antarctica

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