A Day in the Life of a Sea Ice Ecologist

Dr. Lars Chresten Lund-Hansen, sea ice ecologist at Aarhus University in Denmark, recently completed a field campaign in which he and his team collected data and cores from sea ice. The photos below present a day’s work sampling the sea ice near Kangerlussuaq, West Greenland. Read more about this research…

At the first look, not much appears to be going on within the temporary ice sheets that border Greenland and Earth’s polar oceans. Over the years, however, researchers have identified an active community of highly specialized organisms that take advantage of this unique habitat and occupy niches in sea ice and nearly-frozen sea water.

This is the focus of ongoing research by Dr. Lars Chresten Lund-Hansen. Dr. Lund-Hansen and his team recently completed a field campaign in which they collected data and ice cores from sea ice near Kangerlussuaq, Greenland. On slices of the ice cores, they measured a suite of variables, including temperature, salinity, pH, dissolved inorganic carbon, colored dissolved organic carbon (CDOM), chlorophyll-a, primary production, and they collected pulse amplitude modulated (PAM) fluorometry measurements.

Using an LI-192 Underwater Quantum Sensor, they collected time-series data on the intensity of sunlight below the ice with snow cover present and after the snow cover was removed. They found that when snow is on the ice surface, transmission of light through snow and ice is about 4%. When the snow is removed, however, transmission increases to about 65%.

Temperatures at the bottom of the ice are low – around 3 to 4 °C below zero. Nevertheless, algae in the ice were fit for photosynthesis, and Chl-a concentrations in the ice formed a gradient with depth – lowest concentrations near the top and highest concentrations near the seawater.

Among other important observations, they found that the chlorophyll-a concentration rises in sea ice before it rises in the seawater below at the beginning of the spring bloom. This indicates that the ice becomes biologically active at the start of the spring bloom – before the bloom starts in the ocean water. Lund-Hansen’s research suggests that the high chlorophyll-a concentrations found near the sea water – sea ice interface could be explained as a balance between nutrient and light availability, similar to what is observed in the ocean water subsurface Chl-a peaks.

Oceans, sea ice, and aquatic microorganisms are of clear importance to the global climate. Transitional periods such as early spring and late fall are often overlooked due to the difficulty reaching study sites. Dr. Lund-Hansen’s research, however, is providing new information about these important time periods, and it will help close gaps in our understanding of the role of sea ice the oceanic spring.

Acknowledgements: We are grateful to Dr. Lars Chresten Lund-Hansen, Marine Ecology, Institute for Bioscience, Aarhus University, Ole Worms Allé 1, 8000 Aarhus C, Denmark, for contributing to this story and providing photographs.

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This article was originally posted on Wednesday, July 13th, 2011.

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