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  4. Impacts of snow and surface conditions on radiation fluxes through Arctic sea ice during different seasons
 
Zitierlink DOI
10.26092/elib/1456

Impacts of snow and surface conditions on radiation fluxes through Arctic sea ice during different seasons

Veröffentlichungsdatum
2022-01-31
Autoren
Anhaus, Philipp  
Betreuer
Haas, Christian  
Gutachter
Kanzow, Torsten  
Zusammenfassung
Sea ice and its snow cover play a key role within the climate and ecosystem. Due to global environmental changes which are amplified in the Arctic Ocean, its sea-ice cover will primarily consist of thin and young sea ice with a reduction in extent. In particular, the area where snow accumulates reduces and the fraction of melt-pond covered sea ice and of openings in the sea-ice cover such as leads increase. Those changes of the surface conditions strongly influence the partitioning of solar radiation.

The main objective of this dissertation was to establish relationships between the surface conditions that are observed and expected to dominate in the future Arctic and under-ice radiation. A deeper and broader knowledge of such relationships is especially necessary in spring and autumn during which the under-ice radiation can have significant impacts on the annual energy budget. To achieve that, field measurements collected using a variety of instruments during three campaigns for three different sea-ice types, locations, and seasons were analysed and interpreted.

A main result was to derive a new parametrization for snow depth retrieval from spectral under ice-radiation measurements. This was successfully achieved with an accuracy of approximately 5 cm for two ice types, in two locations, during two seasons.

In contrast to the established theory that melt ponds act as bright windows to the underlying ocean, it was possible to document and analyse cases where a thicker snow cover accumulated on melt ponds compared to on adjacent bare ice. This resulted, surprisingly, in lower levels of under-ice radiation underneath the melt ponds than underneath bare ice.

New analyses of relationships between thermodynamics and optics of a refreezing lead and thin ice suggest that radiative transfer in thin ice is often not accurately accounted for using bulk formulations, as they are applicable for thicker ice. The initial states of the lead’s opening and refreezing need to be treated separately and cannot generally be considered windows into the ocean.

This dissertation extended our knowledge of the relationships between snow and surface conditions and under-ice radiation. The results point towards impacts on sea-ice energy balance, ocean heat content, thermodynamic ice growth, and ice-and ocean-associated ecosystem activity.
Schlagwörter
sea ice

; 

Arctic Ocean

; 

solar radiation

; 

transmittance

; 

remotely operated vehicle

; 

snow depth

; 

melt ponds

; 

leads
Institution
Universität Bremen  
Fachbereich
Fachbereich 01: Physik/Elektrotechnik (FB 01)  
Dokumenttyp
Dissertation
Zweitveröffentlichung
Nein
Lizenz
https://creativecommons.org/licenses/by/4.0/
Sprache
Englisch
Dateien
Lade...
Vorschaubild
Name

ANHAUS_2021_PhD_Thesis_version_submitted_20220318_PDF_A_1b_sRGB.pdf

Size

31.61 MB

Format

Adobe PDF

Checksum

(MD5):2fd9fbdcd491af567d0b54de260ef509

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