Description: Major ions were analysed in firn/ice cores located at Fimbul Ice Shelf (FIS), Dronning Maud Land – DML, Antarctica. FIS is the largest ice shelf in the Haakon VII Sea, with an extent of approximately 36 500 km2. Three shallow firn cores (about 20 m deep) were retrieved in different ice-rises, Kupol Ciolkovskogo (KC), Kupol Moskovskij (KM), and Blåskimen Island (BI), while a 100 m long core (S100) was drilled near the FIS edge. These sites are distributed over the entire FIS area so that they provide a variety of elevation (50–400 m a.s.l.) and distance (3– 42 km) to the sea. Sea-salt species (mainly Na+ and Cl−) generally dominate the precipitation chemistry in the study region. We associate a significant six-fold increase in median sea-salt concentrations, observed in the S100 core after the 1950s, to an enhanced exposure of the 100 site to primary sea-salt aerosol due to a shorter distance from the S100 site to the ice front, and to enhanced sea-salt aerosol production from blowing salty snow over sea ice, most likely related to the calving of Trolltunga occurred during the 1960s. This increase in sea-salt concentrations is synchronous with a shift in non-sea-salt sulfate (nssSO42−) toward negative values, suggesting a possible contribution of fractionated aerosol to the sea-salt load in the S100 core most likely originating from salty snow found on sea ice. In contrast, there is no evidence of a significant contribution of fractionated sea-salt to the ice-rises sites, where the signal would be most likely masked by the large inputs of biogenic sulfate estimated for these sites. In summary, these results suggest that the S100 core contains a sea-salt record dominated by the proximity of the site to the ocean, and processes of sea ice formation in the neighbouring waters. In contrast, the ice-rises firn cores register a larger-scale signal of atmospheric flow conditions and a less efficient transport of sea-salt aerosols to these sites. These findings are a contribution to the understanding of the mechanisms behind sea-salt aerosol production, transport and deposition at coastal Antarctic sites, and the improvement of the current Antarctic sea ice reconstructions based on sea-salt chemical proxies obtained from ice cores.

Description: The present dataset contains measurements of density and observations of stratigraphy in the subsurface snow/firn/ice done at Lomonosovfonna during 1997-2015. The variables are named according to the year, when the data was derived: "LF" for Lomonosovfonna and "NN" corresponds to the year, e.g. 97 - 1997, 07 - 2007. Most variables contain the following fields: rho* - density measurements: column 1 - depth of sample top, m; column 2 - depth of sample bottom, m; column 3 - density values, kg m^-3; rho*_reg - density measurements on a regular 1 cm spaced grid, gaps are filled by linear interpolation and extrapolated using "nearest neighbor" logic; column 1 - depth, m; column 2 - density values, kg m^-3; strat - stratigraphy: column 1 - depth of sample top, m; column 2 - depth of sample bottom, m; column 3 - stratigraphy coded as: 1 - snow, 2 - firn, 3 - ice lens; lat* - latitude, degrees to the North of equator; lon* - longitude, degrees to the East of the prime meridian; h* - elevation, m above the sea level. LF97: Six shallow cores were drilled in spring 1997 approximately along the centerline of Nordenskiöldbreen. A system of mass balance stakes at locations of the cores is maintained by Uppsala university. The density is approximated from visual stratigraphic description according to the classification suggested by Pohjola et al., 2002 (see Table 1 there). The density values are the result of averaging of density values ascribed to stratigraphic units identified in core pieces and weighted by their respective thicknesses. LF99: Three shallow cores were drilled in the end of April 1999 at the location where in 1997 a 120 m long ice core was drilled. The cores were drilled along a North-South oriented line with a spacing of 2.5 m between the neighboring cores. The fields in the LF99 variable are named accordingly: fields with the data from the southern location contain "S", northern - "N", central - "C". The field and laboratory work was done by Håkan Samuelsson. Methods and analysis are described in detail in the Master Thesis: "Distribution of melt layers on the ice field Lomonosovfonna, Spitsbergen", defended at Uppsala University in 2001. LF08: One shallow core was drilled by Sanja Forsström, Elisabeth Isaksson, Veijo Pohjola and Jim Hedfors within ca 100 from the location where in 1997 a 120 m long ice core was drilled. Density was measured using two different methods at the cold lab of the Norwegian Polar Institute in Tromso by Sanja Forsström and Tonu Martma. The structure field "rho" contains values calculated from measured geometrical dimensions of the core samples and weights. The fields "rhoDEPcorepieces", "rhoDEPionsamples" and "rhoDEPisotopesamples" contain density values measured using dielectric profiling in three sets of samples. LF12: The core was drilled by Veijo Pohjola and Rickard Pettersson on the 13 of April 2012. Field notes done by Sergey Marchenko. Cold lab operations were done by Sergey Marchenko and Elena Klimenko at the University Centre in Svalbard (UNIS) in Longyearbyen, Norway during 26 April - 3 May 2012. Density was measured in cylindrical and cuboid samples prepared using a band saw to ensure regular shape. The structure field "rho_c" contains density measurements done using cylindrical core pieces. The structure field "rho_rb" contains density measurements done using relatively long cuboid samples prepared from cylindrical core pieces using a band saw. The structure field "rho_rs" contains density measurements done using shorter cuboid samples prepared from the longer pieces using a band saw. The structure field "rho_reg" is based on the "rho_rs" structure field. LF13: The core was drilled by Christian Zdanowics, Dorothee Vallot and Veijo Pohjola in April 2013 and later analyzed by Carmen Vega in the cold lab of the Norwegian Polar Institute in Tromso, Norway. LF14: The core was drilled by Veijo Pohjola and Ward van Pelt in the end of March 2014. Field notes are done by Veijo Pohjola. Cold lab operations were done by Sergey Marchenko, William Kohler and Elisbeth Isaksson in the Norwegian Polar Institute facilities in Tromso, Norway, during 05-10 of October 2014. Density was measured in cylindrical or cuboid samples prepared using a band saw to ensure regular shape. LF15: the core was drilled by Veijo Pohjola and Ward van Pelt on the 15th of April 2015. Field notes are done by Veijo Pohjola. Cold lab operations were done by Sergey Marchenko, Glennda Villanflor and Elisbeth Isaksson in the Norwegian Polar Institute facilities in Tromso, Norway, during 02-05 of November 2015. Density was measured in cylindrical or cuboid samples prepared using a band saw to ensure regular shape.