Caterpillars in camp

The 2011 IGERT cohort spent one week camping outside of Kangerlussuaq in the same site the 2010 cohort chose last year.  The first things we noticed upon arriving at our campsite were the incredible views of the Russell glacier, the Little Ice Age moraine, and the glacial meltwater lakes.

Google map of the area between the IGERT camp near the Russell glacier and the Kangerlussuaq fjord. Air temperatures drop as you drive up the road from Kangerlussuaq to the IGERT camp and the glacier, perhaps offering a gradient useful for studying climate change and insect outbreaks.

But as a close second we noticed that the woody shrubs at the site were all leafless and brown, and that there were many large Lepidoptera larvae (caterpillars) roaming in search of food.  This place had experienced a recent caterpillar outbreak. The larvae that were left had no more food to eat, and they crawled up our tents and boots or into any warm microclimate.  Northern wheatears and snow buntings came in to camp to eat this easy prey off the tents.  Adult moths also flew around in large numbers and we picked them out of our hair and our coffee.  We identified this Lepidoptera species as Eurois occulta, the Great Gray Dart moth known to defoliate the dwarf birch and grayleaf willow common in Greenland.

Caterpillars ate all of the birch and willow leaves around camp, leaving a brown world.

Eurois occulta larva

Eurois occulta adult

However, the entire landscape was not brown.  Many hillsides with similar aspect and distance from the glacier experienced only moderate levels of herbivory and remained green.  Farther from the glacier, back toward Kangerlussuaq and the fjord, the brown outbreak patches disappeared.  Acting on a hot tip from Mike Avery, a PhD student in Eric Post’s lab at Penn State University, we searched for evidence that caterpillars were attacked by a pathogen – desiccated caterpillar corpses draped in the willow leaves.  We found many of these corpses in non-outbreak areas farther from the glacier but did not see any close to the glacier where air temperatures are much cooler.

Some nearby hillsides, however, suffered only slight defoliation.

Closeup of moderate levels of herbivory.

Carcass of a larva infected by a pathogen.

Why are some hillsides completely brown while others remain green?  This is a big question in ecology, and one possible answer is that caterpillars in defoliated areas lack “top-down” controls by predators such as birds, other arthropods, and pathogens.  The caterpillar immune system can fight off infection by pathogens (fungal or viral) but this defense requires a high protein diet.  In plants much of this protein is RuBisCO, a nitrogen-rich enzyme essential for photosynthesis, and the protein content of leaves is expected to decrease as air temperatures get warmer and the growing season gets longer.  Perhaps caterpillars farther from the glacier had less resistance to pathogens because of lower protein content of leaves, or perhaps there are more natural enemies such as birds or arthropods in warmer areas.  The birch/willow shrub tundra of West Greenland is a great ecosystem to test competing explanations for why insect herbivores sometimes outbreak and how climate change may alter the frequency and intensity of these outbreaks.

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Lake changes around Kangerlussuaq

With the greatest effects of climate change expected to be seen in the Arctic, we will likely see major changes in the hydrologic cycle. The lakes in the Kangerlussuaq region of Greenland have unique ecosystems and, because of their great number, play an important role in the surface albedo and local climate of the region.  These lakes are already changing in size and future expansion or contraction of the lake area may result in significant changes in the local water balance, surface albedo, and ecological processes. In order to predict the future changes of these lakes, such as changes in volume, chemical compositions, or ecological processes, we first need to understand the water balance of these lakes and the hydrologic cycle of this region.

There are two main types of lakes around Kangerlussuaq which have different hydrologic regimes. Most of the lakes receive water from precipitation only and because they are in closed basins, lose water primarily through evaporation. The other type of lake is located near the ice sheet and differs from the others by receiving the primary input of water from melting ice, with precipitation playing a lesser role. These inputs and outputs of water are going to be changing as climate change progresses so it is important to understand the current hydrologic cycle before these major shifts occur.

Ben and Sam overlooking meltwater lake

Precipitation fed lakes in Vulgaris Valley

In order to quantify these components of the hydrologic cycle, our group conducted a series of studies on a number of lakes in the Kangerlussuaq region. One of the primary efforts was to collect water samples to be measured for their isotopic composition as the isotopes of water are powerful tools that are used as tracers to understand hydrologic cycle dynamics. In addition, samples were taken to measure the water chemistry, determined the depth of lakes from our boat, identified if lakes were stratified or not, and we used a YSI multiprobe to measure various properties of the water that included temperature, pH, and conductivity. From these measurements, a series of mass balance relationships will be used to best determine the rates of inputs and outputs to these lakes to define a starting point in order to predict future changes.

Sam sampling on dried up lake near camp

The team sampling from boat near the ice sheet

IGERT’s visit historic GISP2 Ice Core site

IGERT's at GISP2 Ice Core borehole

A metal cylinder protrudes from the Greenland Ice Sheet. An IGERT photo opportunity?

Absolutely, considering this metal cylinder changed how humanity views its production of CO2, nitrous oxide, sulfuric and nitric acids, CFC’s and other “greenhouse” gases (U. New Hampshire).

Prior to being a year-round research station, Summit Camp was the drilling site of the Greenland Ice Coring Project (GISP2). Drilled from 1989—1993, GISP2 is the deepest (3053.44 meters) and longest ice core record (>100,000 years) in the northern hemisphere.

The GISP2 ice-core record provides a continuous and detailed record of fluctuations in accumulation and climate variability over central Greenland. The GISP2 ice core, in conjunction with the GRIP deep ice core, revealed that exceptionally large climate changes (more than 20° C warming) can occur over much shorter time periods (5 to 40 years) than previously suspected (Cuffey et al., 1995)

In total, forty-two types of measurements composed the GISP2 deep drilling effort. The borehole, what remains after the conclusion of drilling, is filled with a fluid that keeps the borehole stable/open. The borehole can then be monitored via temperature-logging. The current metal casing may be in need of repair in order to keep the borehole available for future logging. Hopefully the National Science Foundation can find a way to maintain the GISP2 borehole, keeping the historic ice core borehole available for future measurements.

Cuffey, et al., “Large Arctic Temperature Change at the Wisconsin-Holocene Glacial Transition”  Science, Vol. 270, No. 5235, pp. 455-458, Oct. 20th 1995

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