Cruise participant: Christof Pearce

I am a Ph.D. student at the Centre for Past Climate Studies of the Department of Geosciences at Aarhus University in Denmark. My research is on the reconstruction of past sea-surface conditions (temperature and sea-ice variability) in the North Atlantic Subpolar gyre region. For this I am using sedimentological, geochemical and micropalaeontological data with the main focus on diatom analysis.

Diatoms are unicellular algae and are generally the main constituents of the phytoplankton. As primary producers in the upper layers of the ocean, they play a vital role in the marine food web. The cell walls of diatoms have characteristic shapes and ornamentations depending on the species and are made up of silica, resulting usually in excellent preservation in the sediments. Because of the wide variety in species, all with their own ecological preferences (e.g. temperature, salinity, nutrient availability), diatom remains in sediments are ideal indicators of past sea-surface condition.  

At the moment I am studying a gravity core from offshore Newfoundland, that encompasses the Late Glacial to Early Holocene time period (from 12500 to 9500 years ago). In the core, the transition from glacial times to the current Holocene epoch is not smooth and is associated with numerous big climatic fluctuations such as the Younger Dryas, a cold interval when temperatures dropped almost back to glacial levels.

The diatom assemblages clearly reflect these changes as variations in sea-surface temperatures and sea ice presence.The results will be combined with analysis of benthic foraminifera and geochemical parameters to achieve a more comprehensive record. The study of these fluctuations is important to improve our understanding of past and present natural climate variability and will contribute to better future predictions.