Description: Historical sea ice core chlorophyll-a (Chla) data are used to describe the seasonal, regional, and vertical distribution of ice algal biomass in Antarctic landfast sea ice. The analyses are based on the Antarctic Fast Ice Algae Chlorophyll-a data set, a compilation of currently available sea ice Chla data from landfast sea ice cores collected at circum-Antarctic nearshore locations between 1970 and 2015. Ice cores were typically sampled from thermodynamically grown first-year ice and have thin snow depths (mean=0.0520.097m). The data set comprises 888 ice cores, including 404 full vertical profile cores. Integrated ice algal Chla biomass (range: 〈0.1-219.9mg/m(2), median=4.4mg/m(2), interquartile range=9.9mg/m(2)) peaks in late spring and shows elevated levels in autumn. The seasonal Chla development is consistent with the current understanding of physical drivers of ice algal biomass, including the seasonal cycle of irradiance and surface temperatures driving landfast sea ice growth and melt. Landfast ice regions with reported platelet ice formation show maximum ice algal biomass. Ice algal communities in the lowermost third of the ice cores dominate integrated Chla concentrations during most of the year, but internal and surface communities are important, particularly in winter. Through comparison of biomass estimates based on different sea ice sampling strategies, that is, analysis of full cores versus bottom-ice section sampling, we identify biases in common sampling approaches and provide recommendations for future survey programs: for example, the need to sample fast ice over its entire thickness and to measure auxiliary physicochemical parameters. Plain Language Summary Antarctic sea ice is a key driver of physical, chemical, and biological processes in the Southern Ocean. Importantly, sea ice serves as a substrate for microscopic algae which grow in the bottom, interior, and surface layers of the ice. These algae are considered an important food source for Antarctic marine food webs. Using a newly collated database of historical sea ice core chlorophyll-a data (a proxy for ice algal biomass) from coastal sites, we describe the seasonal and vertical variability of algal biomass in Antarctic landfast sea ice. The seasonal chlorophyll-a development is consistent with the current understanding of physical drivers of ice algal biomass, including the seasonal cycle of irradiance and surface temperatures driving landfast sea ice growth and melt. Our analyses show that algae in the lowermost third of ice cores drive the annual cycle of integrated biomass, but internal and surface communities are also important. Through comparison of biomass estimates based on different sea ice sampling strategies, that is, analysis of full cores versus bottom-ice section sampling, we identify biases in common sampling approaches and provide recommendations for future survey programs: for example, the need to sample fast ice over its entire thickness and to measure auxiliary physical parameters, in particular snow-thickness data.

Description: Mineral dust emission and transport can occur at high latitudes, impacting the Earth’s radiative budget and snow albedo. Even though the Arctic region is not often considered as a relevant dust source, in a context of arctic amplification, the importance of high latitude dust (HLD) sources is increasing. Although there is still a lack of knowledge concerning HLD sources and their impact, previous studies have shown how the dust produced there, affects the high Arctic.In this work, we have characterised both potential HLD source areas through the resuspension of soil samples and potential receptor areas through filtration of snow samples. The potential HDL sources considered are Iceland, Alaska and Svalbard Island (Norway), while the second ones, were obtained filtering snow, firn or ice sampled on different Svalbard glaciers. 31 trace elements (TEs) were quantified using tandem ICP-MS on the filters loaded by soil resuspension. Moreover, the Sr and Pb isotope ratios were measured on the whole set of samples using a MC-ICP-MS unit at the A&MS Lab at Ghent University. Specific TEs can be used to recognize different patterns in dust originating from regions characterized by a different geological composition and the analyses of two different isotopic systems is useful in order to differentiate eventual dust sources characterized by overlapping signatures for one of the two elements.The proposed methodology is therefore promising for tracing dust emission and transport in the high Arctic and potentially to reconstruct past circulation patterns by investigating the dust composition in ice cores.