2011 - Cooperative Institute for Research in Environmental Sciences ...

James Sickman
Sabbatical
Ph.D., University of California,
Santa Barbara
Project: Inter-decadal variability
in aquatic ecosystems of the Sierra
Nevada; a synthesis of the 30-year
record from Emerald Lake, Sequoia
National Park
James Sickman is an associate
professor of hydrology at the University of California, Riverside.
His research interests include global environmental
change, biogeochemistry, limnology and environmental
isotopes. Over the last 30 years, he has been compiling
long-term hydrochemical data (such as pH, alkalinity and
nutrient levels) on remote watersheds and lakes in the
Sierra Nevada.
While at CIRES, he will work with William Lewis,
director of the Center for Limnology, to synthesize and
analyze that data. His objective is to better understand
how changes in precipitation and global climate affect the
hydrochemistry and primary productivity (the manufacture
of organic molecules via photosynthesis and chemosynthesis)
of high-altitude aquatic ecosystems. In dry
regions, like the Sierra Nevada, the amount of rain and
snow varies widely with season, year, locale and other
factors, so these watersheds are especially responsive to
environmental changes, such as warming or fluctuations
in snowpack dynamics (depth, duration of snow cover
and time of snowmelt in the spring). One main product of
Sickman’s work will be a book on Sierra Nevada lakes and
aquatic ecosystems, written with his co-investigator, John
Melack, at the University of California, Santa Barbara, and
other colleagues.
Sponsor: William Lewis
Y. Heidi Yoon
Postdoctoral
Ph.D., University of Wisconsin
at Madison
Project: Spectroscopic studies
of Titan particles
Heidi Yoon is working in
Margaret Tolbert’s group characterizing
the optical properties of the
aerosol particles in the atmosphere
of Saturn’s moon Titan. She will
use spectroscopy to study how laboratory analogs of the
particles absorb and scatter different wavelengths of light.
The aerosol particles in Titan’s atmosphere form a
hydrocarbon haze that affects the moon’s surface and air
temperatures. These particles absorb most of the incident
sunlight—keeping it from reaching the surface—but
weakly absorb infrared radiation, allowing thermal heat
to escape. Both properties cool the moon’s surface. Recent
work has suggested that early Earth may have had a
Titan-like haze, so characterizing the optical properties
of that haze is essential for understanding both Titan and
early Earth.
Sponsor: Margaret Tolbert
Dirk van As
Sabbatical
Ph.D., Institute for Marine and
Atmospheric Research in Utrecht
(IMAU), Utrecht University,
The Netherlands
Project: Merging Greenland automatic
weather station networks for increased
accuracy in ice sheet surface mass balance
estimates
Dirk van As is a senior scientist at the Geological Survey
of Denmark and Greenland (GEUS) in Copenhagen.
He studies interactions (such as melting) between the ice
and the atmosphere on the Greenland ice sheet. While at
CIRES, he will work with Konrad Steffen’s group to investigate
the Greenland ice sheet’s surface mass budget—the
annual difference between the mass of snow and ice that
accumulates and the mass that ablates via melting, evaporation
and wind erosion.
The Greenland ice sheet is losing mass at an accelerating
rate, contributing to global sea level rise—a phenomenon
that could affect millions of people living on coastal
areas around the world. Getting an accurate picture of
the ice sheet’s stability and melt rates can help scientists
and policy makers better predict future changes and take
appropriate action. Toward this end, Van As will integrate
data from the CIRES weather station network in
the high regions of the ice sheet and the GEUS network
in the lower regions—for a total of more than 30 weather
stations—to produce a spatial distribution of temperature,
humidity, solar radiation and other parameters crucial for
validating the regional climate models that calculate melt.
Sponsor: Konrad Steffen
CIRES Annual Report 2011 77