Abstract
Glaciers and ice sheets play a crucial role in regulating Earth’s climate by reflecting solar radia-
tion and storing fresh water, with their retreat contributing to sea level rise and impacting water
resources and ecosystems. Glacial melt in the McMurdo Dry Valleys (MDV) is the dominant
source of water for streams, lakes and ecosystems. The MDV climate is sensitive to extreme
weather events, and understanding the meteorological factors influencing glacial melt and accu-
mulation is essential for predicting future changes to this fragile environment. This thesis aims
to investigate the meteorological controls on spatial and temporal variability in ablation and
accumulation of glaciers within the MDV to ultimately anticipate how global warming-induced
changes in weather patterns might impact MDV hydrology and ecosystems.
To address this aim, three research questions are answered by applying methods across multi-
ple scales. The first objective centeres on understanding the impact of foehn wind events on
glacial surface energy balance and melt (Chapter 2). By integrating observations from automatic
weather stations (AWS) with surface energy balance (SEB) modeling and regional weather fore-
casting outputs, the research identifies foehn winds as drivers of enhanced melt rates on glaciers.
Foehn winds increase energy gain through sensible heating but this is largely compensated for
by energy loss due to increased sublimation. The enhanced melt rates are driven by the lowering
of albedo during foehn events, which primes the glacier surface for melt. This chapter also
enhances knowledge on the mechanisms leading to foehn wind signature in the MDV. We show
that isentropic drawdown is responsible for foehn warming at Joyce Glacier and wider southern
MDV, compared to the gap-flow mechanism that was previously found for the northern MDV.
Chapter 3 uses 22 years of AWS data and SEB modelling to further study the impact of foehn
events and other meteorological factors on melt variability. We compare two sites in Taylor
Valley, the coastal Commonwealth Glacier and further inland Taylor Glacier, to study valley-
scale variation in melt environments. At both sites, foehn winds are important in explaining
inter-annual variability in melt. However, especially at Commonwealth Glacier, fluctuations in
albedo are driving melt variability through snow presence and changing ice albedo. Melt at
Taylor Glacier happens mostly with positive air temperatures, often due to foehn winds, while
at Commonwealth Glacier melt happens with negative air temperatures but large net shortwave
radiation. We hypothesise that future melting at Taylor Glacier is sensitive to changes in foehn
wind activity, whereas Commonwealth is influenced by coastal weather modifications affecting
snowfall and albedo.
Because of the importance of snowfall on glacial mass balance, albedo variability and melt, the
snowfall dynamics of the MDV and wider coastal Victoria Land (VL) are examined in Chapter
4. To investigate the moisture origins of precipitation and their connection to weather patterns,
Self-Organizing-Maps (SOM) are combined with Lagrangian moisture source analysis. Moisture
for snowfall in VL primarily originates from the Southern Ocean near Australia and New Zealand,
with increased local sources in the Ross Sea during summer when sea ice is reduced. We show
there is a distinct contrast in moisture sources, with northern VL receiving precipitation from
the west, driven by marine air from lower latitudes, and southern VL obtaining moisture from the
east, transported by cyclonic disturbances in the Ross Sea. Extreme precipitation in northern VL
occurs during anomalous meridional moisture transport, sometimes in the form of atmospheric
rivers. Such strong marine air intrusions do not affect the more isolated western Ross Ice Shelf
and southern VL located further in the Ross Sea embayment.
This thesis highlights the key role of atmospheric events, such as foehn winds and extreme
snowfall events, on glacial ablation and accumulation in the MDV. In the Synthesis (Chapter
5) we discuss the contribution of this thesis to our understanding of the weather and climate
that drives surface melt across Antarctica. We discuss avenues of research to predict the future
climate of the MDV. Future work should study how the synoptic patterns driving extreme events
might change with global warming, as well as the impact of reduced Antarctic sea ice cover on
the MDV through enhanced moisture availability. Furthermore, research gaps remain on the
mesoscale interactions between sea ice and atmosphere in the Ross Sea region that can impact
the MDV climate and glaciers.