Monitoring of thin sea ice within polynyas using MODIS data

• Main Author: Adams, Susanne
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: 2012
• Subjects: Fernerkundung; 4016796-3; Meereis; 4131349-5; MODIS; 4191470-3; Polynja; 4123965-9; Laptewsee; 4377883-5; Geowissenschaften; ddc:550; Antarctic; Arctic; Laptev Sea; Antarc*; laptev; Sea ice
• Online Access: https://ubt.opus.hbz-nrw.de/frontdoor/index/index/docId/559; https://nbn-resolving.org/urn:nbn:de:hbz:385-7818; https://doi.org/10.25353/ubtr-xxxx-8f42-8404; https://ubt.opus.hbz-nrw.de/files/559/Adams_Diss_20120710_final.pdf

Arctic and Antarctic polynya systems are of high research interest since extensive new ice formation takes place in these regions. The monitoring of polynyas and the ice production is crucial with respect to the changing sea-ice regime. The thin-ice thickness (TIT) distribution within polynyas controls the amount of heat that is released to the atmosphere and has therefore an impact on the ice-production rates. This thesis presents an improved method to retrieve thermal-infrared thin-ice thickness distributions within polynyas. TIT with a spatial resolution of 1 km × 1 km is calculated using the MODIS ice-surface temperature and atmospheric model variables within the Laptev Sea polynya for the winter periods 2007/08 and 2008/09. The improvement of the algorithm is focused on the surface-energy flux parameterizations. Furthermore, a thorough sensitivity analysis is applied to quantify the uncertainty in the thin-ice thickness results. An absolute mean uncertainty of -±4.7 cm for ice below 20 cm of thickness is calculated. Furthermore, advantages and drawbacks using different atmospheric data sets are investigated. Daily MODIS TIT composites are computed to fill the data gaps arising from clouds and shortwave radiation. The resulting maps cover on average 70 % of the Laptev Sea polynya. An intercomparison of MODIS and AMSR-E polynya data indicates that the spatial resolution issue is essential for accurately deriving polynya characteristics. Monthly fast-ice masks are generated using the daily TIT composites. These fast-ice masks are implemented into the coupled sea-ice/ocean model FESOM. An evaluation of FESOM sea-ice concentrations is performed with the result that a prescribed high-resolution fast-ice mask is necessary regarding the accurate polynya location. However, for a more realistic simulation of other small-scale sea-ice features further model improvements are required. The retrieval of daily high-resolution MODIS TIT composites is an important step towards a more precise monitoring of thin sea ice and ...