Using High Resolution Satellite Imagery to Determine Light Availability and Primary Production Under a Melting Ice Pack

Increased seasonal ice melt in the Arctic has resulted in a thinner, fractured ice pack with surface melting occurring earlier in the year. Sea ice becomes highly spatially heterogeneous during the melt season, with snow covered ice, bare ice, melt ponds and open water all occurring adjacent to each other. Each of these melt stages attenuates sunlight to a different degree, ranging from almost 100% for snow covered ice to 40 % through melt ponds. Light availability is the primary driver of photosynthesis in the ocean and is tightly coupled to biological activity. Phytoplankton in the Arctic Ocean could bloom prematurely in response to adequate light levels being reached earlier in the year, potentially disrupting a complex food web. Monitoring light availability and primary productivity in the Arctic is crucial for our understanding of these processes, but is often made difficult by inaccessibility to appropriate study sites via shipboard measurements. Satellite remote sensing technology has improved our knowledge of large-scale ocean processes in recent decades, and proves to be a promising solution. However, platforms operated by NASA and NOAA, such as MODIS/VIIRS, are limited by coarse spatial resolution, rendering them ineffective at analyzing fine scale heterogenous environments, including partially melted sea ice. Worldview satellites, operated by Digital Globe, have spatial resolutions of less than 3 meters, allowing for differentiation of smaller features within the ice. Overall light availability in a fractured ice pack can be determined by classifying the ice cover of various images and combining class area coverage with in-situ measurements of light attenuation for each class. Results will provide a light availability estimate that can be incorporated into biological models, which will improve our understanding of when and where under-ice phytoplankton blooms are possible, shedding light on how biological processes may be altered in a changing Arctic environment.