 |
| Titel |
The Bruce Plateau Ice Cap: Upstream Dynamics of the Southern Larsen B Ice Shelf |
| VerfasserIn |
Erin Pettit, Ted Scambos, Martin Truffer, Robert Bauer, Ellen Mosley-Thompson, Victor Zagorodnov, Terry Haran, Ronald Ross, Bryan Blaire, Ian Joughin |
| Konferenz |
EGU General Assembly 2011
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250047792
|
|
|
|
|
|
| Zusammenfassung |
| The Bruce Plateau is a broad, gently undulating ice plateau at 2000 m elevation spanning the
divide of the Antarctic Peninsula near 66o S. The western side is the catchment area for the
glaciers of numerous inlet fjords such as Beascochea and Barilari Bays. The eastern side is
the catchment area for the glaciers of the southern Larsen B Embayment including Flask and
Leppard Glaciers and the northern Larsen C Ice Shelf (Atlee and Cabinet Inlet areas). The
LARISSA Project, an NSF-funded multi-disciplinary investigation of the region, has a series
of observation sites located from the ice divide to the ice shelf: an ice core was drilled to
bedrock in 2010 (447 m of ice), and instruments were installed on the Leppard and
Flask Glaciers, and the Scar Inlet Ice Shelf of the southern Larsen B Embayment.
We present the preliminary results of an observational and modeling analysis of
the dynamics of the Bruce Plateau with respect to its role as the source region for
the glaciers and ice shelves of the Larsen B Embayment and the western outlet
fjords.
We use a suite of data from site installations and remote sensing efforts. Surface
topography data from NASA aircraft (IceBridge Project and preceding data collections) were
augmented with surface-based GPS profiles. We mapped bedrock topography through a
5 MHz Radio Echo Sounding (RES) survey. Near the divide, we also measured the spatial
accumulation pattern and internal structure of the ice to 400 m with a 25 MHz RES survey.
We installed weather stations augmented with firn temperature sensors (at several depths up
to 120 m), accumulation sounder, cameras, and GPS near the divide, on Flask Glacier and the
Scar Inlet Ice Shelf. On upper Leppard and Flask Glaciers we installed continuous GPS
stations. We combined these surface velocity observations with InSAR-derived surface
velocities.
Bedrock topography of the central Bruce Plateau near the ice core site consists of several
hills with relief of several hundred meters. Ice thickness ranges from 200 m above the hills to
more than 700 m deep in the troughs. To the west of the hills, bedrock slopes gently
downward, while surface elevation increases to the crest. Indicating that the ice divide may be
up to 2 km to the west of the local bedrock divide. Our ice-core site is ~ 1km east of the
divide crest, with an ice thickness of 450 m and a surface flow speed of 10±4 m/yr.
Accumulation at the ice core site averaged ~2 meters of ice per year between 1963 and 2010
(estimated from beta radioactivity). Accumulation rates decrease by at least an order of
magnitude towards the Larsen B Embayment. Firn temperatures at the ice core site
indicate a recent mean annual temperature of -15.1o C. Basal ice temperature is
-11.2o C.
Due to the high accumulation rates and strong orographic precipitation pattern across the
Antarctic Peninsula, the Bruce Plateau slopes steeply from the divide and initiates
channelized valley glacier flow within less than 5 km of the ice divide. The strong orographic
precipitation pattern leads to steep (0.1 mean slope), short (20 km to ocean calving face)
glaciers ending in fjords on the warmer, wetter, western side of the Peninsula and more gently
sloping (0.025), longer (75 km) glaciers which end in ice shelves on the colder, drier, eastern
side of the Peninsula.
Recent warming and western-side sea ice loss has likely led to increased accumulation
rates on the western side of the Antarctic Peninsula. Our data suggest a recent (within the top
150 m of internal layering) westward migration of the crest of the ridge. Through a suite a
simple experiments using a finite-element model we show preliminary analyses of the
westward divide migration. |
|
|
|
|
|
|