Charlotte Delcourt @ Glaciologie - ULB
Research
PhD thesis (F.R.I.A. scholarship 2007-2011)
Title:
Dynamics, subglacial hydrology and polythermal regime of
McCall Glacier (Alaska, USA): combined approach by radar
techniques and numerical modelling.
Supervisor: Dr. Frank
Pattyn
The aim
of the project is to investigate dynamics of polythermal
McCall Glacier, Brooks Range, Alaska, USA. Relationships
between subglacial and englacial processes and glacier
dynamics are studied, using a combined radar technique
and numerical modelling approach.
In general, low-frequencies radar measurements (RES) over
a glacier system are converted to ice thickness in order
to map the subglacial topography with sufficiently high
detail. A multilayer electromagnetic reflection model is
developed and used to interpret the variability in basal
reflection power (BRP). As such, the project aims at a
better understanding of the subglacial conditions at the
ice/bed interface from the interpretation of the BRP
signals. Where meltwater is detected, the subglacial
hydrological network is simulated, based on the
calculation of the hydraulic potential gradient, which
governs the direction of subglacial water flow.
The polythermal structure and internal accumulation at
McCall Glacier has been studied in the field during
summer 2010, using high-frequency radar measurements, in
collaboration with Dr. M. Nolan (Univ. Fairbanks, Alaska)
and Dr. Bernhard Rabus (Department of Earth Sciences,
Simon Fraser University, Canada).
A 3D thermomechanical ice flow model using higher-order
stress gradients is also used to determine the thermal
structure and the velocity field of the studied glacier
system. Relations between hydrological properties and
glacier dynamics will be established and introduced in
the existing numerical models to improve our
understanding of subglacial and englacial processes.
These processes are still partly unknown despite their
significant role in the accelerated glacier motion.
McCall Glacier
McCall Glacier is situated at 69°18'N, 143°48'W, in the northeastern part of the Brooks Range, Alaska. The glacier is ~7.6 km long, 120 m thick and covers an area of 6 kmē. It extends from an altitude of 2500 m down to 1365 m at the terminus, with an equilibrium line altitude (ELA) between 2000 to 2400 m. McCall Glacier is known to be a polythermal glacier, with a temperate basal layer along a section of the lower glacier. The glacier has been studied extensively, from IGY (1957-1958) onwards through to the International Hydrological Decade (1969-1972) and the mid 1990s to present. These studies have shown that McCall Glacier has been losing mass for decades, accelerating over the last 10 to 20 years. Moreover, it seems that this well-studied glacier is representative of the other large glaciers of its region. Hence, McCall Glacier is considered as a good indicator for climate change in the Arctic, situated in an area sensitive to climate change.
More info soon...