Climate change is impacting the Arctic Ocean, with the most obvious manifestation of these changes being the reduction in summer sea-ice cover [Boé et al., 2009]. Modeling and observational studies imply that reduced sea-ice in the future will strengthen Arctic primary production (PP) [Arrigo et al., 2008; Pabi et al., 2008]. The biological carbon pump (BCP) is an important component of the global carbon (C) cycle, mainly

driven by the sinking of organic material from the sunlit upper layer of the ocean [Boyd and Trull, 2007]. The fraction of PP that is exported below the euphotic zone (Ez) or below the surface layer (export/primary production, or export efficiency, ThE(Ez)-ratio [Buesseler, 1998; Buesseler and Boyd, 2009]) is a key determinant in how efficiently the BCP sequesters C to depth [Buesseler and Boyd, 2009]. Furthermore, the fraction of this material, which successfully transits deeper into the water column (upper mesopelagic zone) where the majority of remineralization of sinking particulate organic material occurs [Buesseler and Boyd, 2009; Giering et al., 2014], is indicative of BCP efficiency [Buesseler and Boyd, 2009]. The specific ecosystem related processes that drive the considerable variability observed in ThE(Ez)-ratios and further down into the upper mesopelagic remain largely unknown [Buesseler and Boyd, 2009; Giering et al., 2014; Henson et al., 2011] for much of the polar oceans.