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Title: Sensitivity study of Caspian sea ice
Author: Tamura-Wicks, Helen
ISNI:       0000 0004 5922 8050
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2015
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The Northern Caspian lies along the southern-most boundary within the Northern Hemisphere where sea-ice forms. Although ice cover is typically observed between November and March, it experiences high spatio-temporal variabilities. This variability may be of interest in the long-term as it may act as an early indicator of large-scale climate change, as well as being an area of interest to industries and vulnerable species. Through empirical and model studies, this thesis carries out a sensitivity study of Caspian sea-ice for the first time. Caspian sea-ice concentration from satellite passive microwave data and surface daily air temperatures are analysed from 1978 to 2009. Relationships between mean winter air temperatures, cumulative freezing degree days (CFDD) and the sum of daily ice area are found for the first time. Mean monthly air temperatures of less than 5.5-9.5°C, and a minimum CFDD of 3.6-11.2°C, is required for ice formation in the Northern Caspian. Examination of climate projections from multi-model ensembles of monthly mean air temperatures suggest for the first time that the Northern Caspian may be largely ice-free by 2100 for the highest emission scenario. An ocean-ice-atmosphere model of the Caspian shows weak sensitivities of the minimum CFDD to varied sea-ice albedo and ice compressive strength. Sea level decline reduces the minimum CFDD and promotes formation of higher concentration ice. An atmosphere model of the Caspian is run with observed 2006 to 2009 sea-ice cover, with an additional run without ice cover, to quantify the sensitivity of the atmosphere to sea-ice for the first time. Ice cover removal results in up to 5-10% increase in precipitation, surface wind speeds and humidity, with up to 3°C increase in surface temperature, in the December-January-February climatology over the Northern Caspian. Additionally, extreme precipitation and extreme wind speeds intensify and extreme cold air events weaken with ice removal.
Supervisor: Toumi, Ralf Sponsor: Engineering and Physical Sciences Research Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available