Paul R. Holland

British Antarctic Survey

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Adrian Jenkins

Northumbria University

Pierre Dutrieux

British Antarctic Survey

D. L. Feltham

Centre for Polar Observation and Modelling

Adrian Luckman

Swansea University

Alberto C. Naveira Garabato

University of Southampton

Suzanne Bevan

Swansea University

Bernd Kulessa

Swansea University

Michael P. Meredith

British Antarctic Survey

Thomas J. Bracegirdle

British Antarctic Survey

Satoshi Kimura

Japan Agency for Marine-Earth Science and Technology

Cooperative Institutions

British Antarctic Survey

101

Natural Environment Research Council

Centre National de la Recherche Scientifique

National Oceanography Centre

University of Cambridge

University of East Anglia

University of Southampton

Centre for Polar Observation and Modelling

Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung

University of Leeds

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West Antarctic ice loss influenced by internal climate variability and anthropogenic forcing

Nature Geoscience (2019)

Paul R. Holland Thomas J. Bracegirdle Pierre Dutrieux Adrian Jenkins Eric J. Steig

Forcing (mathematics)

Antarctic ice sheet

Future sea level

10.1038/s41561-019-0420-9

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Citations (264)

Marine ice in Larsen Ice Shelf

Geophysical Research Letters (2009)

Paul R. Holland Hugh F. J. Corr David G. Vaughan Adrian Jenkins Pedro Skvarca

It is argued that Larsen Ice Shelf contains marine ice formed by oceanic freezing and other mechanisms. Missing basal returns in airborne radar soundings and observations of a smooth and healed surface coincide downstream of regions where an ocean model predicts freezing. Visible imagery suggests that marine ice currently stabilizes Larsen C Ice Shelf and implicates failure of marine flow bands in the 2002 Larsen B Ice Shelf collapse. Ocean modeling indicates that any regime change towards the incursion of warmer Modified Weddell Deep Water into the Larsen C cavity could curtail basal freezing and its stabilizing influence.

10.1029/2009gl038162

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Citations (160)

An abrupt transition in the Antarctic sea ice–ocean system

F. Alexander Haumann François Massonnet Paul R. Holland Mitchell Bushuk Ted Maksym

Over the past decade, Antarctic sea ice extent exhibited a sequence of record maxima, followed by a rapid decline in 2015/16, and record minima since. In this presentation, we show that this sudden and remarkable ice loss marks an abrupt transition from a high to a low ice state that cannot be explained by year-to-year variability. Instead, it is most likely associated with a longer term variability arising from ice–ocean feedbacks. The abrupt transition was preceded by a multi-decadal increase in persistence and variance of the sea ice anomalies, an increasing upper Southern Ocean density stratification, and an accumulation of heat at the subsurface; suggesting a decoupling of the surface from the subsurface ocean. During this period, the sea ice anomalies shifted from being structured predominantly regionally and seasonally to a largely circumpolar and interannual regime. In 2015/16, the upper ocean density stratification in the ice-covered region suddenly weakened, leading to a release of heat from the subsurface, contributing to the sea ice decline during winter. Our analysis suggests that the sudden sea ice loss in 2015/16, and the persisting low ice conditions since, arose from a systematic change in the physical state of the coupled circumpolar ice–ocean system. This change will have wide implications for global climate, ecosystems, and the Antarctic Ice Sheet.

Antarctic ice sheet

Stratification (seeds)

10.5194/egusphere-egu23-8749

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Comment on tc-2021-371

Antony Siahaan Robin S. Smith Paul R. Holland Adrian Jenkins Jonathan M. Gregory

Abstract. The Antarctic Ice Sheet will play a crucial role in the evolution of global mean sea level as the climate warms. An interactively coupled climate and ice sheet model is needed to understand the impacts of iceâclimate feedbacks during this evolution. Here we use a two-way coupling between the UK Earth System Model and the BISICLES (Berkeley Ice Sheet Initiative for Climate at Extreme Scales) dynamic ice sheet model to investigate Antarctic iceâclimate interactions under two climate change scenarios. We perform ensembles of SSP1â1.9 and SSP5â8.5 (Shared Socioeconomic Pathway) scenario simulations to 2100, which we believe are the first such simulations with a climate model that include two-way coupling of atmosphere and ocean models to dynamic models of the Greenland and Antarctic ice sheets. We focus our analysis on the latter. In SSP1â1.9 simulations, ice shelf basal melting and grounded ice mass loss from the Antarctic Ice Sheet are generally lower than present rates during the entire simulation period. In contrast, the responses to SSP5â8.5 forcing are strong. By the end of the 21stÂ century, these simulations feature order-of-magnitude increases in basal melting of the Ross and FilchnerâRonne ice shelves, caused by intrusions of masses of warm ocean water. Due to the slow response of ice sheet drawdown, this strong melting does not cause a substantial increase in ice discharge during the simulations. The surface mass balance in SSP5â8.5 simulations shows a pattern of strong decrease on ice shelves, caused by increased melting, and strong increase on grounded ice, caused by increased snowfall. Despite strong surface and basal melting of the ice shelves, increased snowfall dominates the mass budget of the grounded ice, leading to an ensemble mean Antarctic contribution to global mean sea level of a fall of 22âmm by 2100 in the SSP5â8.5 scenario. We hypothesise that this signal would revert to sea-level rise on longer timescales, caused by the ice sheet dynamic response to ice shelf thinning. These results demonstrate the need for fully coupled iceâclimate models in reducing the substantial uncertainty in sea-level rise from the Antarctic Ice Sheet.

Ice-sheet model

Greenland ice sheet

Antarctic ice sheet

Future sea level

Ice-albedo feedback

10.5194/tc-2021-371-rc1

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The nonlocal impacts of Antarctic subglacial runoff

Authorea (Authorea) (2023)

Daniel Goldberg Andrew G Twelves Paul R. Holland Martin Wearing

Little is known about Antarctic subglacial hydrology, but based on modeling, theory and indirect observations it is thought that subglacial runoff enhances submarine melt locally through buoyancy effects. However, no studies to date have examined effects of runoff on sea ice and circulation on the continental shelf. Here we use modeled and observational estimates of runoff to force a regional model of the Amundsen Sea Embayment. We find that runoff enhances melt locally (i.e. within the ice-shelf cavity), increasing melt at Thwaites ice shelf by up to 15 Gt/a given estimates of steady runoff, and up to 25 Gt/a if runoff is episodic as remote sensing measurements suggest. However runoff also has smaller nonlocal effects through freshwater influence on flow and stratification. We further find that runoff reduces summer sea-ice volume over the continental shelf (by up to 10\% with steady runoff but over 30\% with episodic runoff). Furthermore runoff is much more effective at reducing sea ice than an equivalent volume of ice-shelf meltwater – due in part to the latent heat loss associated with submarine melting. Results suggest that runoff may play an important role in continental shelf dynamics, despite runoff flux being small relative to ice-shelf melting – and that runoff-driven melt and circulation may be an important process missing from regional Antarctic ocean models.

Meltwater

10.22541/essoar.167870419.99885664/v1

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Citations (2)

Ice-Ocean Interactions on the Antarctic Peninsula (Invited)

AGUFM (2010)

Paul R. Holland

Peninsula

Iceberg

Source

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Comment on tc-2023-16

Gemma K. O’Connor Paul R. Holland Eric J. Steig Pierre Dutrieux Gregory J. Hakim

Abstract. Glaciers in the Amundsen Sea Embayment of West Antarctica are rapidly retreating and contributing to sea level rise. Ice loss is occurring primarily via exposure to warm ocean water, which varies in response to local wind variability. There is evidence that retreat was initiated in the mid-20^th century, but the perturbation that may have triggered retreat remains unknown. A leading hypothesis is that large pressure and wind anomalies in the 1940s drove exceptionally strong oceanic ice-shelf melting. However, the characteristics, drivers, and rarity of the atmospheric event remain poorly constrained. We investigate the 1940s atmospheric event using paleoclimate reconstructions and climate model simulations. The reconstructions show that large westerly wind anomalies occurred from ~1938–1942, a combined response to the very large El Niño event from 1940–1942 and other variability beginning years earlier. Climate model simulations provide evidence that events of similar magnitude and duration are unusual but may have occurred tens to hundreds of times throughout the Holocene. Our results suggest that the 1940s westerly event is unlikely to have been exceptional enough to be the sole explanation for the initiation of Amundsen Sea glacier retreat. Naturally arising variability in ocean conditions prior to the 1940s, or anthropogenically driven trends since the 1940s, may be needed to explain the onset of retreat in West Antarctica.

Paleoclimatology

10.5194/tc-2023-16-rc2

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The Effect of a New Drag-Law Parameterization on Ice Shelf Water Plume Dynamics

Journal of Physical Oceanography (2007)

Alexander V. Wilchinsky D. L. Feltham Paul R. Holland

Abstract A drag law accounting for Ekman rotation adjacent to a flat, horizontal boundary is proposed for use in a plume model that is written in terms of the depth-mean velocity. The drag law contains a variable turning angle between the mean velocity and the drag imposed by the turbulent boundary layer. The effect of the variable turning angle in the drag law is studied for a plume of ice shelf water (ISW) ascending and turning beneath an Antarctic ice shelf with draft decreasing away from the grounding line. As the ISW plume ascends the sloping ice shelf–ocean boundary, it can melt the ice shelf, which alters the buoyancy forcing driving the plume motion. Under these conditions, the typical turning angle is of order −10° over most of the plume area for a range of drag coefficients (the minus sign arises for the Southern Hemisphere). The rotation of the drag with respect to the mean velocity is found to be significant if the drag coefficient exceeds 0.003; in this case the plume body propagates farther along and across the base of the ice shelf than a plume with the standard quadratic drag law with no turning angle.

10.1175/jpo3093.1

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Recent recovery of Antarctic Bottom Water formation in the Ross Sea driven by climate anomalies

Nature Geoscience (2020)

Alessandro Silvano Annie Foppert Stephen R. Rintoul Paul R. Holland Takeshi Tamura

Antarctic Bottom Water

Abyssal zone

Antarctic ice sheet

10.1038/s41561-020-00655-3

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Citations (99)