The spatial heterogeneity of Arctic landscapes presents
unique challenges to measuring and modeling a wide variety of land surface processes.
One that is of particular importance to the NGEE Arctic project is the
distribution of temperatures within active layer soils and permafrost. This
applies to both the profile of temperature with depth in the soil and variation
in temperature across the microtopography of ice-wedge polygons. Many of our
team members would like to have good measurements of temperature not only for
understanding its importance in controlling CO2 and CH4
flux, but also for validation of our fine-scale models where the challenge is
in simulating freeze-thaw processes at fairly high resolution.
Knowing the important role played by temperature in
Arctic ecosystems our scientists have deployed a number of temperature probes
at field sites on the BEO. Currently we have a dense network of probes that
measure temperatures across polygon centers, rims, and troughs to a depth of
1.5 meters. Many of these datasets are available at the NGEE Arctic data
portal.
Not surprisingly, every year a suite of new research tasks
are added to our existing activities. And when that happens, additional probes also
frequently need to be installed. This trip Bob, Go, and Sina each had tasks
that required new temperature measurements. Interestingly, their need for new temperature
measurements were driven by a range of science questions at fine, intermediate,
and large spatial scales.
Sina and Bob were interested in the temperature of
shallow soils so they spent much of the last two days installing a dozen
Stevens Hydra Probe II sensors within the upper several centimeters of soil at
our intensive study sites. Sina placed probes within the soil, ran cables back
to the data logger and Bob did the wiring. The data loggers had to be
reprogrammed but Bob was able to do that fairly quickly despite surprisingly
cold temperatures and intermittent rain. Sina will use these temperature
measurements in conjunction with information that she derives from the infrared
(IR) camera that is mounted atop a 10-meter tower on the BEO. These
measurements taken at two different scales will provide information that will
help us interpret spatial heterogeneity in temperatures across the landscape.
Similarly, Go installed temperature and moisture probes at 15 to 20
locations on the BEO last fall. Yesterday and today he downloaded data from
each of those and recorded their position with GPS. Go was happy with the
quality of data that he has acquired and with the lack of problems encountered given
that the probes were left in place over the winter. However, despite his best
efforts one or two of the data loggers had been damaged by lemmings or foxes.
This kind of damage plagues all researchers, but seems to be an especially
acute problem in the Arctic. We should be pleased that only one or two data
loggers needed to be replaced. Go plans to continue measuring temperatures at
broad spatial scale across the BEO for several more years so he can evaluate
surface temperatures from the NASA Soil Moisture Active Passive (SMAP) mission
(http://www.nasa.gov/smap/). This will
help the NGEE Arctic project in several ways, but most importantly in
translating what we measure at fine scales to spatial scales relevant to
climate models.
