Graduate Thesis Or Dissertation
Detecting Recent Snow Accumulation and Meltwater Storage in Firn Aquifers on Ice Sheets Using Remote and Field Observations Public Deposited
Mass loss from ice sheets has been identified as a major contributor to sea level rise by the Intergovernmental Panel on Climate Change from detailed observations in the past few decades. In order to understand how sea level rise will be influenced by ice sheets, we must quantify their total mass balance (through surface mass fluxes and ice discharge) over time. This dissertation focuses on the component of surface mass balance, presenting new in-situ and remote observations of accumulation and meltwater storage in firn aquifers.
In Chapter 2, I present the 2018 Surface Mass Balance and Snow on Sea Ice Working Group database, a standardized, formatted, community-based dataset housed at the Arctic Data Center. It consists of sub datasets of density, accumulation, 10 m borehole temperatures, and snow depth on sea ice measurements. I analyze temporal and spatial patterns across the Greenland Ice Sheet and conclude that observations are oversampled in higher elevation, colder regions and undersampled at warmer, lower elevations. In addition, there was a large temporal gap from 2000 into more recent decades, but since then that has been reconciled in the 2019 and 2020 SUMup database releases.
In Chapter 3, I use NASA’s Operation IceBridge airborne snow radar to derive annual accumulation over 8 consecutive years (2009-2017) in Southeast Greenland, the highest snowfall region on the ice sheet which largely influences the sign of the mass balance. I compare these derived accumulations with two regional climate models, the Modèle Atmosphérique Régional version 3.9 (MAR) and the Regional Atmospheric Climate Model version 2.3p2 (RACMO2), to evaluate model biases. Results indicate that MAR agrees with the derived accumulations well, but underestimates interannual variability while RACMO2 underestimates accumulation but is able to capture the interannual variability.
Finally, in Chapter 4, I present hydrological and geophysical observations of meltwater storage and flow in a firn aquifer on the Wilkins Ice Sheet, Antarctica and its impact on ice shelf stability. Results from a borehole dilution test, slugs tests, ground penetrating radar, and groundwater flow modeling show that the aquifer is highly permeable and flowing into a nearby rift. Based on these observations and model output, we conclude that the aquifer is likely not in steady state near our measurement site, could have influenced past ice shelf breakups, and may impact ice shelf stability in the future.
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