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Lidar profiles of Arctic plankton layers and their dependence on sea ice conditions
  • James Churnside
James Churnside

Corresponding Author:[email protected]

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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.