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Adusumilli, S, Fricker HA, Siegfried MR, Padman L, Paolo FS, Ligtenberg SRM.  2018.  Variable basal melt rates of Antarctic Peninsula ice shelves, 1994-2016. Geophysical Research Letters. 45:4086-4095.   10.1002/2017gl076652   AbstractWebsite

We have constructed 23-year (1994-2016) time series of Antarctic Peninsula (AP) ice-shelf height change using data from four satellite radar altimeters (ERS-1, ERS-2, Envisat, and CryoSat-2). Combining these time series with output from atmospheric and firn models, we partitioned the total height-change signal into contributions from varying surface mass balance, firn state, ice dynamics, and basal mass balance. On the Bellingshausen coast of the AP, ice shelves lost 84 +/- 34Gt a(-1) to basal melting, compared to contributions of 50 +/- 7 Gt a(-1) from surface mass balance and ice dynamics. Net basal melting on the Weddell coast was 51 +/- 71 Gt a(-1). Recent changes in ice-shelf height include increases over major AP ice shelves driven by changes in firn state. Basal melt rates near Bawden Ice Rise, a major pinning point of Larsen C Ice Shelf, showed large increases, potentially leading to substantial loss of buttressing if sustained.

Beem, LH, Tulaczyk SM, King MA, Bougamont M, Fricker HA, Christoffersen P.  2014.  Variable deceleration of Whillans Ice Stream, West Antarctica. Journal of Geophysical Research-Earth Surface. 119:212-224.   10.1002/2013jf002958   AbstractWebsite

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.

Paolo, FS, Fricker HA, Padman L.  2015.  Volume loss from Antarctic ice shelves is accelerating. Science.   10.1126/science.aaa0940   AbstractWebsite

The floating ice shelves surrounding the Antarctic Ice Sheet restrain the grounded ice-sheet flow. Thinning of an ice shelf reduces this effect, leading to an increase in ice discharge to the ocean. Using eighteen years of continuous satellite radar altimeter observations we have computed decadal-scale changes in ice-shelf thickness around the Antarctic continent. Overall, average ice-shelf volume change accelerated from negligible loss at 25 ± 64 km3 per year for 1994-2003 to rapid loss of 310 ± 74 km3 per year for 2003-2012. West Antarctic losses increased by 70% in the last decade, and earlier volume gain by East Antarctic ice shelves ceased. In the Amundsen and Bellingshausen regions, some ice shelves have lost up to 18% of their thickness in less than two decades.