Decadal-scale variations in ice flow along Whillans Ice Stream and its tributaries, West Antarctica

Stearns, L. A.; Jezek, Kenneth C.; Veen, C. J. van der

doi:10.3189/172756505781829610

Cited by 37 publications

(52 citation statements)

References 59 publications

(167 reference statements)

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“…One reconstruction scenario therefore encompasses (i) a phase of drumlinization accompanying ice-margin retreat into the southern Bothnian Sea, (ii) margin retreat proceeding across flowset B, followed by (iii) a re-advancing pulse of a newly triggered ice stream (flowset A). Stearns et al 2005;Catania et al 2012). An alternative scenario does not invoke significant margin retreat and re-advance.…”

Section: Stage 2: Bothnian Sea Ice-stream Eventmentioning

confidence: 83%

The Bothnian Sea ice stream: early Holocene retreat dynamics of the south‐central Fennoscandian Ice Sheet

Greenwood

Clason

Nyberg

et al. 2016

Boreas

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The Gulf of Bothnia hosted a variety of palaeo‐glaciodynamic environments throughout the growth and decay of the last Fennoscandian Ice Sheet, from the main ice‐sheet divide to a major corridor of marine‐ and lacustrine‐based deglaciation. Ice streaming through the Bothnian and Baltic basins has been widely assumed, and the damming and drainage of the huge proglacial Baltic Ice Lake has been implicated in major regional and hemispheric climate changes. However, the dynamics of palaeo‐ice flow and retreat in this large marine sector have until now been inferred only indirectly, from terrestrial, peripheral evidence. Recent acquisition of high‐resolution multibeam bathymetry opens these basins up, for the first time, to direct investigation of their glacial footprint and palaeo‐ice sheet behaviour. Here we report on a rich glacial landform record: in particular, a palaeo‐ice stream pathway, abundant traces of high subglacial meltwater volumes, and widespread basal crevasse squeeze ridges. The Bothnian Sea ice stream is a narrow flow corridor that was directed southward through the basin to a terminal zone in the south‐central Bothnian Sea. It was activated after initial margin retreat across the Åland sill and into the Bothnian basin, and the exclusive association of the ice‐stream pathway with crevasse squeeze ridges leads us to interpret a short‐lived stream event, under high extension, followed by rapid crevasse‐triggered break‐up. We link this event with a c. 150‐year ice‐rafted debris signal in peripheral varved records, at c. 10.67 cal. ka BP. Furthermore, the extensive glacifluvial system throughout the Bothnian Sea calls for considerable input of surface meltwater. We interpret strongly atmospherically driven retreat of this marine‐based ice‐sheet sector.

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Section: Stage 2: Bothnian Sea Ice-stream Eventmentioning

confidence: 83%

The Bothnian Sea ice stream: early Holocene retreat dynamics of the south‐central Fennoscandian Ice Sheet

Greenwood

Clason

Nyberg

et al. 2016

Boreas

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“…Our results and earlier studies in the region (Joughin et al, 2002(Joughin et al, , 2005 show that dynamic changes in the region are ongoing. Stearns et al (2005) suggest a change of basal conditions as the cause of velocity changes in upper Whillans Ice Stream. The authors speculate that the depletion of meltwater at the base of the ice stream is most likely responsible for the observed changes.…”

Section: Discussionmentioning

confidence: 99%

Ice velocity changes in the Ross and Ronne sectors observed using satellite radar data from 1997 and 2009

2012

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Abstract. We report changes in ice velocity of a 6.5 million km 2 region around South Pole encompassing the Filchner-Ronne and Ross Ice Shelves and a significant portion of the ice streams and glaciers that constitute their catchment areas. Using the first full interferometric synthetic aperture radar (InSAR) coverage of the region completed in 2009 and partial coverage acquired in 1997, we processed the data to assemble a comprehensive map of ice speed changes between those two years. On the Ross Ice Shelf, our results confirm a continued deceleration of Mercer and Whillans Ice Streams with a 12-yr velocity difference of −50 m yr −1 (−16.7 %) and −100 m yr −1 (−25.3 %) at their grounding lines. The deceleration spreads 450 km upstream of the grounding line and more than 500 km onto the shelf, beyond what was previously known. Ross and Filchner Ice Shelves exhibit signs of pre-calving events, representing the largest observed changes, with an increase in speed in excess of +100 m yr −1 in 12 yr. Other changes in the Ross Ice Shelf region are less significant. The observed changes in glacier speed extend on the Ross Ice Shelf along the ice streams' flow lines. Most tributaries of the Filchner-Ronne Ice Shelf show a modest deceleration or no change between 1997 and 2009. Slessor Glacier shows a small deceleration over a large sector. No change is detected on the Bailey, Rutford, and Institute Ice Streams. On the Filchner Ice Shelf itself, ice decelerated rather uniformly with a 12-yr difference in speed of −50 m yr −1 , or −5 % of its ice front speed, which we attribute to a 12 km advance in its ice front position. Our results show that dynamic changes are present in the region. They highlight the need for continued observation of the area with a primary focus on the Siple Coast. The dynamic changes in Central Antarctica between 1997 and 2009 are generally second-order effects in comparison to losses on glaciers in the Bellingshausen and Amundsen Seas region and on the Antarctic Peninsula. We therefore conclude that the dynamic changes shown here do not have a strong impact on the mass budget of the Antarctic continent.

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“…The edge of the ice stream was defined as where the surface velocity deviates from interstream ridge velocities, functionally 5 m/yr. Change in ice steam width,

\overset{W}{true}

, was taken from previous studies [ Bindschadler and Vornberger , ; Stearns et al , ], B m , i are estimated to be 700 kPa yr 1/3 and 500 kPa yr 1/3 , respectively, when n was taken equal to 3. U and

\overset{U}{true}

were taken from the velocity data sets described above.…”

Section: Basal Resistance Modelingmentioning

confidence: 99%

Variable deceleration of Whillans Ice Stream, West Antarctica

et al. 2014

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The Whillans Ice Stream Ice Plain (WIP) has been slowing since at least 1963. Prior constraints on this slowdown were consistent with a constant long-term deceleration rate. New observations of ice velocity from 11 continuous and 3 seasonal GPS sites indicate the deceleration rate varies through time including on interannual time scales. Between 2009 and 2012 WIP decelerated at a rate (6.1 to 10.9 ± 2 m/yr 2 ) that was double the multidecadal average (3.0 to 5.6 ± 2 m/yr 2 ). To identify the causes of slowdown, we used new and prior velocity estimates to constrain longitudinal and transverse force budget models as well as a higher-order inverse model. All model results support the conclusion that the observed deceleration of WIP is caused by an increase in basal resistance to motion at a rate of 10 to 40 Pa/yr. Subglacial processes that may be responsible for strengthening the ice stream bed include basal freeze on, changes in subglacial hydrology, or increases in the area of resistant basal substrate through differential erosion. The observed variability in WIP deceleration rate suggests that dynamics in subglacial hydrology, plausibly driven by basal freeze on and/or activity of subglacial lakes, plays a key role in modulating basal resistance to ice motion in the region.

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Decadal-scale variations in ice flow along Whillans Ice Stream and its tributaries, West Antarctica

Abstract: ABSTRACT. We investigate velocity changes occurring along Whillans

Cited by 37 publications

References 59 publications

The Bothnian Sea ice stream: early Holocene retreat dynamics of the south‐central Fennoscandian Ice Sheet

The Bothnian Sea ice stream: early Holocene retreat dynamics of the south‐central Fennoscandian Ice Sheet

Ice velocity changes in the Ross and Ronne sectors observed using satellite radar data from 1997 and 2009

Variable deceleration of Whillans Ice Stream, West Antarctica

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