Estimation of turbulent heat flux over leads using satellite thermal images
<p>Sea ice leads are an important feature in pack ice in the Arctic. Even covered by thin ice, leads can still serve as prime windows for heat exchange between the atmosphere and the ocean, especially in the winter. Lead geometry and distribution in the Arctic have been studied using optical a...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2019-06-01
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| Series: | The Cryosphere |
| Online Access: | https://www.the-cryosphere.net/13/1565/2019/tc-13-1565-2019.pdf |
| Summary: | <p>Sea ice leads are an important feature in pack ice in the
Arctic. Even covered by thin ice, leads can still serve as prime windows for
heat exchange between the atmosphere and the ocean, especially in the
winter. Lead geometry and distribution in the Arctic have been studied using
optical and microwave remote sensing data, but turbulent heat flux over
leads has only been measured on-site during a few special expeditions. In
this study, we derive turbulent heat flux through leads at different scales
using a combination of surface temperature and lead distribution from remote
sensing images and meteorological parameters from a reanalysis dataset.
First, ice surface temperature (IST) was calculated from Landsat-8 Thermal
Infrared Sensor (TIRS) and Moderate Resolution Imaging Spectroradiometer
(MODIS) thermal images using a split-window algorithm; then, lead pixels
were segmented from colder ice. Heat flux over leads was estimated using two
empirical models: bulk aerodynamic formulae and a fetch-limited model with
lead width from Landsat-8. Results show that even though the lead area from
MODIS is a little larger, the length of leads is underestimated by 72.9 %
in MODIS data compared to TIRS data due to the inability to resolve small
leads. Heat flux estimated from Landsat-8 TIRS data using bulk formulae is
56.70 % larger than that from MODIS data. When the fetch-limited model was
applied, turbulent heat flux calculated from TIRS data is 32.34 % higher
than that from bulk formulae. In both cases, small leads accounted for more
than a quarter of total heat flux over leads, mainly due to the large area,
though the heat flux estimated using the fetch-limited model is 41.39 %
larger. A greater contribution from small leads can be expected with larger
air–ocean temperature differences and stronger winds.</p> |
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| ISSN: | 1994-0416 1994-0424 |