Part 1)
Locations and volume-range estimates for 125 active lakes under the
Antarctic ice sheet found in this study, shown as points color-coded
by the volume range. Background shading shows a combination of
satellite-radar-derived surface velocities (Joughin and others, 2006, Joughin and others, 1999) and balance velocities(Bamber and others, 2008). Magenta outlines represent previously-published lake locations: outlines are drawn for Lake Vostok (Studinger and others, 2003), the
Recovery Glacier lakes (Bell and others, 2007), and active lakes
mapped with radar altimetry in Adventure Trench (Wingham and others,
2006), and with InSAR on Kamb Ice Stream (Gray and others, 2005).
Lakes mapped from airborne radar are represented by magenta circles of
diameter equal to the lake length given by (Siegert and others, 2005).
Green lines show approximate extent of streaming and tributary flow
for selected glaciers.
Part 2) Top: Illustration of how changes in eleveation recorded by ICESat reveal the locations of subglacial lakes. ICESat tracks are shown over the catchment of Academy Glacier. ICESat tracks with little elevation are shown in black, and tracks for which the total elevation
range for all valid repeat passes exceed 0.5 m are color-coded by the
elevation range (color scale at right). Areas where these changes indicate subglacial lakes are shown with magenta boundaries. Ice stream catchment boundaries are shown by dashed
white lines. The area of relatively large surface slopes, over
which ICESat elevation errors are expected to produce large errors,
is shown by a dashed green outline. Background image is the MODIS
Mosaic of Antarctica (Scambos and others, 2007).
Middle left and center: elevation displacements relative to the Fall 2003 campaign for two ICESat tracks (see AB and CD in top plot for location; AB is track 96, CD is track 243) across a filling lake in
the upper Academy Glacier catchment. Colors of points correspond to
the time of each profile, as shown at right. Middle right: Estimated
volume history for this lake relative to the Fall 2003 ICESat campaign.
Bottom: Sequential gridded displacement estimates for eleven ICESat
campaigns, color code given at right. The letters at the bottom of
each plot give the months and years of the campaigns.
[click to enlarge]
Collaborative Research: Elevation Change Anomalies in West Antarctica - Do They Provide Constraints on Subglacial Water Transport Beneath Ice Streams and Their Tributaries?
Summary
We are using field and remote sensing data to investigate Elevation Change Anomalies (ECAs) discovered recently in the Ross Sea sector of the West Antarctic Ice Sheet (WAIS), which reveal the filling and draining of subglacial lakes. Through the remote sensing research component based at UW, we are determining the spatial distribution of subglacial lakes for the entire continent using ICESAT elevation data. These data complement the ground based GPS observations being acquired through the UCSC led field effort.
Our analysis of the ICESAT data detected 124 lakes that were active during this period 5.5 year period where these we acquired. These ICESat-detected lakes are prevalent in coastal Antarctica, and are present under most of the largest outlet drainage systems. Lakes sometimes appear to transfer water from one to another, but also often exchange water with distributed sources not detectable by ICESat, suggesting that the lakes may provide water to or withdraw water from the reservoirs that lubricate glacier flow. This may allow lake activity to produce rapid temporal changes in glacier speeds.
