Improving arctic sea ice thickness estimates from satellite altimetry
Satellite observations have shown that the arctic sea ice extent has strongly decreased during the last 40 years, with a clear increase of the shrinking since the 90's. While the mechanisms responsible for this accelerated shrinking are relatively well known, sea ice models do not clearly repro...
Main Author: | |
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Other Authors: | , , , , , , |
Format: | Doctoral or Postdoctoral Thesis |
Language: | French |
Published: |
HAL CCSD
2017
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Subjects: | |
Online Access: | https://tel.archives-ouvertes.fr/tel-02924618 https://tel.archives-ouvertes.fr/tel-02924618/document https://tel.archives-ouvertes.fr/tel-02924618/file/2017TOU30277b.pdf |
Summary: | Satellite observations have shown that the arctic sea ice extent has strongly decreased during the last 40 years, with a clear increase of the shrinking since the 90's. While the mechanisms responsible for this accelerated shrinking are relatively well known, sea ice models do not clearly reproduce the observed extent variations. This inaccurate representation is generally attributed to a misunderstanding of the arctic system climate feedbacks. Among these feedbacks, we seek to study one of them in particular: the sea ice thinning. Sea ice thinning is generally associated with an earlier seasonal melt as well as an increase in sea ice export; both tend to accelerate the sea ice retreat. A good representation of sea ice thickness is therefore necessary to improve our understanding of the arctic sea ice extent variations observed during the last decades. Unlike sea ice extent data, there are currently no pan-Arctic sea ice thickness observations covering a large period (> 20 years). However, several studies have demonstrated the potential of satellite altimetry to retrieve sea ice thickness at a basin scale. To measure sea ice thickness from radar altimetry, the "freeboard" technique is generally employed. This methodology consists of estimating the thickness of the emerged sea ice (freeboard) from radar altimetry and then converting this measurement to sea ice thickness, using an equation for the hydrostatic equilibrium that exists between the snow covered sea ice and the ocean. The freeboard methodology has been applied to diverse altimetric missions (ERS-2, Envisat and CryoSat-2) since 1995 and should allow the retrieval of more than 20 years of pan-Arctic ice thickness. However, the previous estimates of sea ice thickness are data shorter than 6 years in duration. This absence of a long ice thickness time series is mostly due to the difficulty in providing continuity between the different altimetric missions (conventional altimetry/SAR altimetry) as well as to the uncertainties related to the ... |
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