Concentration of organic compounds in aerosols and surface waters of the East Atlantic and Antarctic

The data on content and composition of lipids and aliphatic hydrocarbons (HC) in aerosols and surface waters obtained during the spring-summer periods of 2001 and 2003 along the vessel route from the North Sea to the Antarctic and backwards are presented. It was shown that the distribution of organic compounds is caused by influence of zonal supply of eolian matter from land, anthropogenic, and marine autochtonous sources. Concentrations of organic compounds in the aerosols varied from 0.22 to 13.04 ng/m**3 for lipids and from 0.04 to 7.03 ng/m**3 for aliphatic HC; in surface waters, it from 9 to 84 and from 1 to 53 µg/l, respectively. There is correlation between fluxes of lithogenic fraction of the aerosols, HC, and lipids. Growth of productivity in the aquatic area increases levels of the HC in the surface waters but to a lower degree than HC supply with oil contamination.

Mineral dust deposition in interglacial and glacial climate conditions: model results

The global aerosol/climate model ECHAM5-HAM is used in order to investigate the dust cycle for four interglacial and one glacial climate conditions. The 20-year time-slices are the pre-industrial control (CTRL), mid-Holocene (6000 years BP), last glacial inception (115000 years BP), Eemian (126000 years BP) and Last Glacial Maximum (LGM) (21000 years BP) time intervals. The study is focused on the Antarctic region. The model is able to reproduce the magnitude order of dust deposition globally for the pre-industial and LGM climates. Correlation coefficient of the natural logarithm of the observed and modeled values is 0.78 for the CTRL and 0.81 for the LGM. For the pre-industrial simulation the model overestimates observed values in Antarctica by a factor of about 2-3 due to overestimation of the Australian dust source and too high wet deposition in the Antarctica interior. In the LGM, the model underestimates dust deposition in eastern Antarctica by a factor of about 4-5 due to underestimation of the South American dust source. More records are needed to validate dust deposition for the past interglacial time-slices. The modeled results show that dust deposition in Antarctica in the past interglacial time-slices is higher than in the CTRL simulation. The largest increase of dust deposition in Antarctica is simulated for the LGM, showing about 10-fold increase compared to CTRL.

Geochemistry of frost flowers and snow obtained near Ahlmann summit, Vestfonna ice cap

The chemistry of snow and ice cores from Svalbard is influenced by variations in local sea ice margin and distance to open water. Snow pits sampled at two summits of Vestfonna ice cap (Nordaustlandet, Svalbard), exhibit spatially heterogeneous soluble ions concentrations despite similar accumulation rates, reflecting the importance of small-scale weather patterns on this island ice cap. The snow pack on the western summit shows higher average values of marine ions and a winter snow layer that is relatively depleted in sulphate. One part of the winter snow pack exhibits a [SO4-/Na+] ratio reduced by two thirds compared with its ratio in sea water. This low sulphate content in winter snow is interpreted as the signature of frost flowers, which are formed on young sea ice when offshore winds predominate. Frost flowers have been described as the dominant source of sea salt to aerosol and precipitation in ice cores in coastal Antarctica but this is the first time their chemical signal has been described in the Arctic. The eastern summit does not show any frost flower signature and we interpret the unusually dynamic ice transport and rapid formation of thin ice on the Hinlopen Strait as the source of the frost flowers.

Aerosols over the East Atlantic in spring and summer 2001

Data on the concentration and mineral composition of aerosols collected by nets in Cruise 18 of R/V Akadernik Fedorov on a submeridional section in the East Atlantic are presented. An empirical curve for calculating efficiency factor of a net is given for different concentrations of mineral part of aerosols. Fluxes of lithogenic part of aerosols to the sea surface are calculated. A comparison of lithogenic fluxes from the atmosphere and in the water column of the ocean showed that values of fluxes practically coincide in areas with dominating supply of dry atmospheric material. These fluxes strongly differ in the intratropical convergence zone, where deposition of aerosols depends on atmospheric precipitation, or in regions, where sedimentary material is supplied to the ocean mainly by river run-off. Residence time of aerosol lithogenic matter in the euphotic layer is calculated.