Publications and Presentations

In this thesis, I have used remote sensing and modeling techniques to investigate Antarctic
ice shelf surface hydrology with the purpose of answering three key questions: 1) How do surface
drainage systems evolve over a typical summertime melt season, over several consecutive meltseasons, and over several decades? 2) What controls the expansion of surface hydrology
networks? and 3) Will surface drainage expand into areas vulnerable to hydrofracture and
important for buttressing when meltwater volume increases in a warmer, future climate?

In Chapter 1, our analysis of satellite observations of Amery Ice Shelf’s surface drainage
networks suggests that their downstream extent varies inter-annually, that this variability is not
simply the result of inter-annually variability in melt rates, and that ice-shelf topography plays a
crucial role. Consecutive years of extensive melting lead to year-on-year expansion of the
drainage system, potentially through a link between melt production, refreezing in firn, and the
maximum extent of the lakes at the downstream termini of drainage. These mechanisms are
important when evaluating the potential of drainage systems to grow in response to increased
melting, delivering meltwater to areas of ice shelves vulnerable to hydrofracture.

In Chapter 2, we use high resolution elevation data to delineate hydrologic catchments on
Amery, Roi Baudouin, Larsen C, Nivlisen, and Riiser-Larsen Ice Shelves. We compare our results
spatially with modelled present-day melt production, future melt predictions, and stress-based
vulnerability to hydrofracture, to examine the controls on these hydrologically important
characteristics of the topography. The high volume elevation data present computational
challenges that cannot be overcome with traditional data analysis workflows. Therefore,
pre-processing for catchment delineation is made possible by parallelizing these tasks with the
computational power of cloud-based cluster computing. Catchments with high basin volumes are
found clustered near grounding lines and nunataks, and these catchments are bordered
down-glacier by broader, low volume catchments. We hypothesize that once meltwater
production fills these catchments, we should expect to see overflow of meltwater, extending
drainage systems downstream to the calving fronts or into areas vulnerable to hydrofracture.

In Chapter 3, we use the filtered, digital elevation data from Chapter 2 as the input for an
idealized water routing model of the eastern and western Amery Ice Shelf, Nivlisen Ice Shelf, and
Roi Baudouin Ice Shelf to investigate this drainage network expansion. In our comparison with
previous observational studies, we find that our modelled drainage networks show similar
drainage network patterns, despite having several discrepancies in drainage network arrangement
and water ponding locations. We use our model to investigate the expansion of the drainage
network with average annual melt from the regional climate model RACMO. In one model run,
we use the spatial distribution of average annual melt from an overlapping RACMO subset, in the
other, we input a spatially-averaged melt production of the same subset of RACMO. We compare
the results of these simulations to investigate if the expansion of these drainage systems is
controlled predominantly by near-surface climate via water input, or if topography also plays a
role. We find variability both between drainage systems and within a single drainage system, and
that within all of our selected drainage systems, topography exerts some control over expansion.
The responsiveness of a drainage network system to spatially variable meltwater input may affect
how susceptible the system is to expansion, thus the spatial distribution of melt input must be
represented in an ice shelf stability projection model.

As melt input increases in a warmer future Antarctic, it will be increasingly important to
understand how surface melting may affect ice shelf stability. This thesis shows several
proof-of-concept approaches towards modelling future expansion of surface drainage networks on
Antarctic ice shelves. We find that the spatial variability of melt does impact the expansion rate of
drainage networks across ice shelf areas potentially vulnerable to hydrofracture. This thesis posits
that with more year-on-year meltwater drainage system growth, meltwater-induced hydrofracture
may become an increasingly regular occurrence on Antarctic ice shelves.