Report Number: 33788
Permit Number: CRLA-2005-SCI-0001
Current Status: Checked in
Date Received: Dec 28, 2005
Reporting Year:
2005
Principal Investigator:
Ms Lora Koenig,
University of Washington,
Department of Earth and Space Sciences,
Seattle, WA
Additional investigator(s):
Julia C. Jarvis
Park-assigned Study Id. #
CRLA-00004
Permit Expiration Date:
Jun 30, 2005
Permit Start Date:
Jan 01, 2005
Study Starting Date:
Jan 01, 2005
Study Ending Date:
Jun 30, 2005
Study Status:
Completed
Activity Type:
Research
Subject/Discipline:
Glaciers
Objectives:
There are three main purposes of
this study:
a) to investigate the changes of snow’s
thermal
conductivity with depth
b) to create a highly spatially sampled snow
grain size
dataset
c) to create an in-situ dataset that can be
used with a variety of space-borne sensors
d) to determine the temporal variability of
nitrate (NO3-)
isotopes in snow at Crater Lake
e) to test field methods for later use in
Antarctica
General Purpose:
Remote sensing of snow properties is the
future of snow science. Satellites have the ability to determine spatially
distributed snow properties on a daily basis in inhospitable areas (Dozier and
Painter, 2004). However there is a dearth of in-situ measurements collected
specifically for satellite ground tracks. This research will begin to fill in
this void of information by collecting a spatial and depth distributed ground
dataset for sensor calibration. This dataset will include depth dependant
information on thermal conductivity and snow grain size. This depth component is
important for satellite sensors, such as passive microwave sensors, that record
emission some distance into the snow. The deep snow pack at Crater Lake National
Park is an ideal location for studying changes in snow parameters with depth.
A specific focus on the changes in thermal
conductivity in snow will elucidate how snow properties affect a new model
developed by Winebrenner (et al., 2004). Winebrenner developed a new
relationship between microwave brightness temperatures and physical surface
temperature over Antarctica. This relationship depends on a characteristic time
scale of emission, which is defined as the inverse of the microwave extinction
coefficient and the thermal diffusivity of snow. Using this relationship Koenig
(et al., 2004) showed that the characteristic time scale of emission co-varied
with accumulation rate near Byrd Station, Antarctica. In order to understand why
the characteristic time scale co-varies with accumulation rate more needs to be
known about the changes in thermal conductivity, an unknown variable in thermal
diffusion. Sturm (et al., 1997) has summarized work to date on thermal
conductivity of seasonal snow. This work neglects changes in thermal
conductivity with depth. The investigators want to use the deep Crater Lake snow
pack to look at depth dependant thermal conductivity profiles. The study will
also allow for testing of field techniques that will eventually be conducted in
Antarctica.
Snow grain size scatters microwave emissions
and can affect the extinction coefficient. Multiple space-borne sensors are
being used to estimate snow grain size (Painter et al., 2003). Collecting grain
size data will allow investigators to evaluate current grain size retrieval
methods and analyze their applicability in Antarctica. The relationship between
grain size and thermal conductivity will also be studied.
In addition to the snow properties study,
snow samples will also be collected to determine the temporal variability of
nitrate (NO3-) isotopes in snow at Crater Lake. Nitrate deposition in snow and
rainwater is the dominant sink for nitrogen oxides (NOx = NO + NO2) in the
atmosphere, the sources of which include fossil fuel combustion, biomass
burning, soil emissions, and lightning. Previous studies suggest that nitrate
isotopes may contain information as to the sources of NOx to a region (e.g.
Hastings et al., 2003). Collection of fresh snow at Crater Lake, where heavy
snowfall likely removes all of the atmospheric nitrate and nitric acid in the
region, and subsequent isotopic analysis of nitrate will add spatial variability
to prior studies of nitrate in snow from Greenland and Antarctica (Hastings et
al., 2004; Jarvis et al., unpublished data).
Findings and Status: The 2004-2005
winter snowpack at Crater Lake National Park was used to study spatial and depth
dependant changes in snow thermal conductivity. This research was used to test
equipment and methodology to be used in 2006 on the Greenland and Antarctic ice
sheets. Over large portions of the Antarctic ice sheet a link has been
established between passive microwave emission, accumulation rate and thermal
conductivity (Koenig et al., in prep). The link to accumulation rate, which
influences sea level change, motivates studies of thermal conductivity changes
over space and with depth.
Eleven snow pits were dug within skiing
distance of the plowed road connecting Crater Lake lodge to Oregon Highway 62.
The following methodology was used for all snow pits. The pits were sampled
every 10 cm for snow thermal conductivity, density, grain size, hardness,
temperature and crystal type. Thermal conductivity was measured directly in the
snowpack using a transient-state probe (Jackson and Taylor, 1986). The probe
heats the snow and then measures the cooling curve to obtain a thermal
conductivity measurement. In order to take a thermal conductivity measurement
the snowpack must be below -3 degrees Celsius to prevent a phase change during
the heating cycle. Temperature was measured with a dial thermometer. Density was
measured with a 1000 cc density cutter. A hand hardness test was used to measure
the grain bonding and the crystal type was recorded using the International
Classification for Seasonal Snow on the Ground (Colbeck et al., 1990).
In total 77 good thermal conductivity
measurements were obtained. According to a published review article by Sturm et
al. (1997), the 77 thermal conductivity measurements from Crater Lake National
Park comprise the second largest thermal conductivity dataset from a specific
location. Preliminary results show that that there was no significant change in
thermal conductivity with depth or space. The spatial result was expected
because to the homogeneous nature of the Cascade snowpack. The mean thermal
conductivity of all measurements was .161 W/m K, the minimum .047 W/m K, the
maximum .392 W/ m K and the standard deviation was .07. The mean thermal
conductivity of 842 previous published measurements in seasonal snow is .215 W/m
K; the mean thermal conductivity of the snowpack at Crater Lake, .161 W/m K, is
less than the previous measurements (Sturm et al., 1997). The mean density of
the snowpack was 296 Kg/m3. The majority of the snow crystals were well rounded
with a grain size larger than .5 mm.
Sterile snow samples were taken directly
after and during snow storms to sample for nitrate concentrations. Approximately
10 samples were taken during the Crater Lake field season. These samples are
waiting to be processed in the lab and results are expected by the end of 2006.
For this study, were one or
more specimens collected and removed from the park but not destroyed during
analyses?
No
Funding provided this
reporting year by NPS:
0
Funding provided this
reporting year by other sources:
500
Full name of college or
university: n/a
Annual funding provided by
NPS to university or college this reporting year: 0
