Premium
The spectral albedo of sea ice and salt crusts on the tropical ocean of Snowball Earth: II. Optical modeling
Author(s) -
Carns Regina C.,
Light Bonnie,
Warren Stephen G.
Publication year - 2016
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
eISSN - 2169-9291
pISSN - 2169-9275
DOI - 10.1002/2016jc011804
Subject(s) - snowball earth , albedo (alchemy) , crust , snow , sea ice , radiative transfer , geology , atmospheric sciences , ice albedo feedback , cloud albedo , environmental science , cryosphere , climatology , geophysics , sea ice thickness , cloud cover , geomorphology , optics , glacial period , art , physics , performance art , art history , cloud computing , operating system , computer science
During the Snowball Earth events of the Neoproterozoic, tropical regions of the ocean could have developed a precipitated salt lag deposit left behind by sublimating sea ice. The major salt would have been hydrohalite, NaCl•2H 2 O. The crystals in such a deposit can be small and highly scattering, resulting in an allwave albedo similar to that of snow. The snow‐free sea ice from which such a crust could develop has a lower albedo, around 0.5, so the development of a crust would substantially increase the albedo of tropical regions on Snowball Earth. Hydrohalite crystals are much less absorptive than ice in the near‐infrared part of the solar spectrum, so their presence at the surface would increase the overall albedo as well as altering its spectral distribution. In this paper, we use laboratory measurements of the spectral albedo of a hydrohalite lag deposit, in combination with a radiative transfer model, to infer the inherent optical properties of hydrohalite as functions of wavelength. Using this result, we model mixtures of hydrohalite and ice representing both artificially created surfaces in the laboratory and surfaces relevant to Snowball Earth. The model is tested against sequences of laboratory measurements taken during the formation and the dissolution of a lag deposit of hydrohalite. We present a parameterization for the broadband albedo of cold, sublimating sea ice as it forms and evolves a hydrohalite crust, for use in climate models of Snowball Earth.