[pccgrads] [PhD defense] Gergel on "Modeling the changing roles of snow and permafrost in mid- and high-latitude climate systems"

UW Program On Climate Change uwpcc at uw.edu
Tue Oct 8 06:58:32 PDT 2019

Diana Gergel
Computational Hydrology group in Civil and Environmental Engineering is
defending her PhD!

Thursday, Oct. 24th at 3:30 pm
in More Hall, Room 221.

*Title: Modeling the changing roles of snow and permafrost in mid- and
high-latitude climate systems*

Diana has been an active participant in the Program on Climate Change,
serving on the inaugural PCC Graduate Student Steering Committee
(PGraSC) in 2017 and completing her Graduate Certificate in Climate Science
capstone while partnering with the Northwest Climate Science Center (now
the NWCASC) to tailor their climate science digest to the climate science
needs of their constituents. She wrote about her project in the blog
post "Mapping
climate science needs and networks in the Pacific Northwest through
evaluation of a climate science newsletter". <http://MAPPING CLIMATE

*Her dissertation abstract:*
The land surface plays a key role in local and regional climates at mid-
and high-latitudes as well as in the global climate system. Consequently,
changes in snow and permafrost affect other parts of the climate system. In
this dissertation, we explore the role of the land surface in the
cryosphere, with a particular focus on high latitudes, using a hierarchy of
standalone land surface models (LSMs), fully-coupled regional climate
models (RCMs) and global climate models (GCMs). In Chapter 2, I describe
simulated changes in snowpack and fire potential in the western US using
the Variable Infiltration Capacity (VIC) hydrology model under future
climate projections for an ensemble of GCMs from the Coupled Model
Intercomparison Project (CMIP5) archive for two Representative
Concentration Pathways (RCPs), RCP 4.5 and RCP 8.5. Large losses of
snowpack and increases in fire potential are projected to occur in the
mountainous parts of the western US in the 21st century, whereas increases
in fire potential are much more uncertain in lowland regions due to large
uncertainty in precipitation projections.

In Chapter 3, I draw on two modeling ensembles, the Community Earth System
Large Ensemble (CESM-LE) and the CESM Low Warming Ensemble (CESM-LWE), to
understand projected changes in snow and how these changes will affect soil
thermal regimes and permafrost in the 21st century over the circumpolar
Arctic for three levels of warming: 1.5°C, 2°C and RCP 8.5. Even for the
lower emissions scenarios represented by the 1.5°C and 2°C global-mean
warming pathways, the majority of the Arctic is projected to experience
significant decreases in Snow Water Equivalent (SWE), while parts of
Eurasia will experience substantial increases. Large losses of permafrost
are projected due to a significant warming of the soil column by the end of
the 21st century. Soil organic carbon (SOC) stocks are highly vulnerable
and loss of permafrost could result in potentially large losses of carbon
to the atmosphere.

In Chapter 4, I describe the process of designing a new parameter set for
application over a pan-Arctic domain in version 5 of the VIC hydrology
model (VIC-5) and in the Regional Arctic System Model (RASM), a
fully-coupled regional climate model. Simulated streamflow in RASM
simulations is significantly higher than in standalone VIC-5 simulations
and much more closely matches observations, while simulated permafrost in
standalone VIC-5 simulations more closely approximates observed permafrost
extent, illustrating the difficulties of designing land surface parameters
for application in a land surface model that is used in both standalone and
fully-coupled modeling contexts.

Program on Climate Change at the University of Washington
Office Phone: 206-543-6521
uwpcc at uw.edu
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