Taking a planetary science-inspired look at Earth’s sea ice-ocean interface – a hot spot for interactions of life, chemical and physical exchange.

On Earth, sea ice at high latitudes harbors microbial and small multicellular life forms, as does the ocean-ice boundary. This is a rich zone of biological-chemical exchange which fuels marine food webs and provides resources to the sea floor in polar oceans. Although how this translates to ocean worlds in the outer solar system is not known, it has motivated us to take a second look at the interactions of melting-freezing dynamics, and the associated biosignatures that are produced beyond physical life forms themselves. On Earth, the sun powers life at this interface, yet in the dark of polar winter, life still thrives, although is not as well understood. Heterotrophic microbial processes in brines and perhaps chemoautotrophic processes proceed in the dark. We will present a brief review the nutrient biogeochemistry, carbon cycling, and life forms both in the ice on earth and those that life at the interface, and discuss the implications of this interface system to potentially detecting biosignatures either entrained in ice shells, or on an eventual mission aiming to study the ice-water interface itself.