New insights into radiative transfer in sea ice derived from autonomous ice internal measurements

• Main Authors: Katlein, Christian, Valcic, Lovro, Lambert Girard, Simon, Anhaus, Philipp, Nicolaus, Marcel, Hoppmann, Mario
• Format: Conference Object
• Language: unknown
• Published: 2021
• Subjects: Arctic; ice pack; North Pole; Sea ice
• Online Access: https://epic.awi.de/id/eprint/53619/; https://epic.awi.de/id/eprint/53619/1/AF_Talk_Katlein_long_true.pdf; https://hdl.handle.net/10013/epic.c85d4dc8-70a6-46ad-97c3-0fbe693a8e4f

The radiative transfer of short-wave solar radiation through the sea ice cover of the polar oceans is a crucial aspect of energy partitioning at the atmosphere-ice-ocean interface. A detailed understanding of how sunlight is reflected, absorbed and transmitted by the sea ice cover is needed for an accurate representation of critical processes in climate and ecosystem models, such as the ice-albedo feedback. Due to the challenges associated with ice internal measurements, most information about radiative transfer in sea ice has been gained by optical measurements above and below the sea ice. To improve our understanding of radiative transfer processes within the ice itself, we developed an innovative, chain-type instrument equipped with up to 64 multispectral light sensors that can be frozen into the ice. Here we present the results of a first prototype deployment at the North Pole in fall of 2018, as well as recently acquired data from the MOSAiC drift expedition in spring and summer 2020. We discuss the advantages, application, and limits of the device and provide first new insights into the spatiotemporal aspect of radiative transfer within the sea ice itself. In particular, we investigate how measured attenuation coefficients relate to the optical properties of the ice pack, and show that sideward planar irradiance measurements are equivalent to measurements of total scalar irradiance. We also show how this light sensor chain can be used for assessment of the temporal evolution in ice algal biomass and water column properties.