Lidar profiles of Arctic plankton layers and their dependence on sea ice
conditions
Abstract
Airborne lidar surveys were used to characterize subsurface layers of
phytoplankton in the Arctic Ocean during the latter half of July 2014
and again during the latter half of July 2017. The survey region
included US waters in the Beaufort and Chukchi Seas. In 2014, layers
were detected in open water and also in openings in pack ice where up to
90% of the surface was covered by ice. The layers in the pack ice were
less prevalent, weaker, and shallower than those in open water. Layers
were more prevalent in the Chukchi Sea than in the Beaufort Sea. Three
quarters of the layers observed were thinner than 5 m. In 2017, ice
conditions were significantly different. The ice edge was farther north
at the beginning of the measurement period in 2017 and retreated faster
during that period. As a result, flights were conducted in the areas
surveyed in 2014 in addition to areas near the ice edge. Data analysis
of the 2017 flights will be done in the same way as the 2014 data. Low
clouds and fog are common in the Arctic. The lidar can operate through
optically thin clouds and fog, but at some point, the beam is completely
attenuated. Data where the atmospheric attenuation is too great must be
removed from consideration by visual inspection. Detection of ice in the
lidar return is straightforward, since ice produces a saturated return
in the lidar receiver. Subsurface layers will be identified by visual
inspection of the data, and the characteristics will be calculated.
Subsurface layers are clearly present in the data, and their
characteristics will be presented, along with a comparison between 2014
and 2017 results.