title: Influence of ice thickness and surface properties on light transmission through Arctic sea ice.
abstract: The observed changes in physical properties of sea ice such as decreased thickness and increased melt pond cover severely impact the energy budget of Arctic sea ice. Increased light transmission leads to increased deposition of solar energy in the upper ocean and thus plays a crucial role for amount and timing of sea-ice-melt and under-ice primary production. Recent developments in underwater technology provide new opportunities to study light transmission below the largely inaccessible underside of sea ice. We measured spectral under-ice radiance and irradiance using the new Nereid Under-Ice (NUI) underwater robotic vehicle, during a cruise of the R/V Polarstern to 83°N 6°W in the Arctic Ocean in July 2014. NUI is a next generation hybrid remotely operated vehicle (H-ROV) designed for both remotely piloted and autonomous surveys underneath land-fast and moving sea ice. Here we present results from one of the first comprehensive scientific dives of NUI employing its interdisciplinary sensor suite. We combine under-ice optical measurements with three dimensional under-ice topography (multibeam sonar) and aerial images of the surface conditions. We investigate the influence of spatially varying ice-thickness and surface properties on the spatial variability of light transmittance during summer. Our results show that surface properties such as melt ponds dominate the spatial distribution of the under-ice light field on small scales (<1000 m2), while sea ice-thickness is the most important predictor for light transmission on larger scales. In addition, we propose the use of an algorithm to obtain histograms of light transmission from distributions of sea ice thickness and surface albedo.
authors.affiliation: Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung Bremerhaven Germany; Jacobs University Bremen Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Katlein
authors.affiliation: Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung Bremerhaven Germany.
authors.forename: Stefanie
authors.initials: S
authors.lastname: Arndt
authors.affiliation: Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung Bremerhaven Germany.
authors.forename: Marcel
authors.initials: M
authors.lastname: Nicolaus
authors.affiliation: Cold Regions Research and Engineering Laboratory Hanover New Hampshire USA.
authors.forename: Donald K
authors.initials: DK
authors.lastname: Perovich
authors.affiliation: Woods Hole Oceanographic Institution, Deep Submergence Laboratory Woods Hole Massachusetts USA.
authors.forename: Michael V
authors.initials: MV
authors.lastname: Jakuba
authors.affiliation: Woods Hole Oceanographic Institution, Deep Submergence Laboratory Woods Hole Massachusetts USA.
authors.forename: Stefano
authors.initials: S
authors.lastname: Suman
authors.affiliation: Woods Hole Oceanographic Institution, Deep Submergence Laboratory Woods Hole Massachusetts USA.
authors.forename: Stephen
authors.initials: S
authors.lastname: Elliott
authors.affiliation: Woods Hole Oceanographic Institution, Deep Submergence Laboratory Woods Hole Massachusetts USA; Johns Hopkins University, Department of Mechanical Engineering Baltimore Maryland USA.
authors.forename: Louis L
authors.initials: LL
authors.lastname: Whitcomb
authors.affiliation: Johns Hopkins University, Department of Mechanical Engineering Baltimore Maryland USA.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: McFarland
authors.affiliation: Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung Bremerhaven Germany; Jacobs University Bremen Germany.
authors.forename: Rüdiger
authors.initials: R
authors.lastname: Gerdes
authors.affiliation: Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung Bremerhaven Germany; Max Planck Institute for Marine Microbiology Bremen Germany.
authors.forename: Antje
authors.initials: A
authors.lastname: Boetius
authors.affiliation: Woods Hole Oceanographic Institution, Deep Submergence Laboratory Woods Hole Massachusetts USA.
authors.forename: Christopher R
authors.initials: CR
authors.lastname: German
keywords: ROV; albedo; light transmittance; melt ponds; shortwave radiation; spatial variability