A millennium of variable ice flow recorded by the Ross Ice Shelf, Antarctica

Abstract

An enhanced composite Advanced Very High Resolution Radiometer (AVHRR) image is used to map flow stripes and rifts across the Ross Ice Shelf, Antarctica. The patterns of these flow-related features reveal a history of discharge variations from the ice streams feeding the eastern part of the shelf.The most profound variations are visible in the track of rifts downstream of Crary Ice Rise, flow-stripe bends to the west of this ice rise and adjacent to Steershead ice rise, and changes in the northern margin of Ice Stream B. The track of rifts downstream of Crary Ice Rise indicates that the ice rise has existed for at least 700 years.The character of this track changes about 350 km downstream, indicating a rearrangement of flow patterns about 550 years ago. The large bulge in the flow stripes to the west of Crary Ice Rise is shown in detail, with bent flow stripes extending for several hundred kilometers along flow; this feature formed from the south, possibly due to a change in the discharge of Ice Stream A. The AVHRR image documents a complex history associated with the shutdown of Ice Stream C, with changes in the margins of Ice Stream C and the northern margin of Ice Stream B, and the grounding of Steershead ice rise with an associated bending and truncation of flow stripes. Landsat imagery shows a region that appears to be actively extending just downstream of the ice rise, as the shelf continues to respond to recent changes in ice-stream discharge. We present a four-stage flow history which accounts for the features preserved in the ice shelf.

Continued deceleration of Whillans Ice Stream, West Antarctica

“…This is important since flow-stripes preserved in the ice shelf suggest differing flow histories across the ice rise [Fahnestock et al, 2000]. In 2004, we deployed 28 stations covering the ice plain's full width.…”

Ice-flow reorganization within the East Antarctic Ice Sheet deep interior

“…Primary evidence includes: englacial layer geometry indicative of ground-line migration and non-steady flow patterns (Siegert et al 2013;Kingslake et al 2016); small length-scale englacial folding thought to represent ice-stream convergent flow where there is presently slow flow (Bingham et al 2007(Bingham et al , 2015; and surface flow structure in a presently slow-flowing region (Glasser et al 2015). Additionally, buried crevasses in Kamb Ice Stream and Siple Dome suggest a stagnation of ice streams (Retzlaff & Bentley 1993;Jacobel et al 2000), flow stripe variability observed on the Ross Ice Shelf supports cyclical ice streaming activity with a frequency of between 100 and 1000 years (Fahnestock et al 2000), and variations in englacial radar reflector geometry are thought to show flow reorganization (Ng & Conway 2004;Siegert et al 2004). Most evidence for flow reorganization exists near ice-sheet margins but reorganization may be expected along the full length of the ice flow path.…”

Subglacial Lake Whillans microbial biogeochemistry: a synthesis of current knowledge

“…SLW is a shallow lake under the Whillans Ice Plain that is part of the greater Siple-Gould Coast system of ice streams, which are responsible for draining about one-third of the West Antarctic Ice-Sheet [35]. Until 2005, most lakes discovered in Antarctica were found in deep troughs and detected using classic radar techniques.…”