NP-seminar: Phytoplankton and light under Arctic Ocean sea ice: vertical extents and seasonal trends

Ved: Samuel Laney, Woods Hole Oceanographic Institution, Massachusetts, USA.

Under-ice observations of algal biomass and light levels are critical for understanding better how climate-driven changes affect polar ocean ecosystems. However, seasonal and interannual variability in these properties have been studied sparsely in perennially ice-covered polar ocean regions.

To address this gap in polar ocean observing, bio-optical sensors for measuring chlorophyll fluorescence, optical scattering, dissolved organic matter fluorescence, and incident solar radiation were integrated into Ice-Tethered Profilers (ITPs), and 8 such systems were deployed in the Arctic Ocean between 2011 and 2013. These ITPs conducted profiles up to 4 times per day, where such temporal resolution allows for more accurate assessment of

  • the timing of the onset of the growing season in the water column
  • the subsequent export of particulate organic matter at the end
  • the frequency of intermittent perturbations

These observations also provided important information regarding the magnitude and seasonality of the under-ice light field, for which a new model was developed to estimate euphotic zone depth over seasonal time scales.