Aerosol particle elemental size distributions during the Arctic Ocean

The central Arctic Ocean is a region that is particularly sensitive to changes in climate due to various feedback mechanisms that exist there. During the arctic summer, aerosol particles influence the radiative balance primarily by acting a cloud condensation nuclei, knowledge of the sources and properties of these particles being essential for an adequate assessment of future climate changes in the Arctic region. As part of an atmospheric research programme, aerosol samples were collected on filters (SFU: Stacked Filter Unit) and cascade impactors (an LPI: a Dekati Low-Pressure Impactor; and an SDI: a Small Deposit Impactor) during an expedition to the Arctic Ocean in the summer of 2001 on the Swedish icebreaker Oden. The aerosol samples were analyzed by PIXE (Particle Induced X-ray Emission) to obtain information concerning their size-resolved elemental composition. The elements Si, S, Cl, K, Ca, Ti, Fe, Zn and Br were usually found in concentrations above their detection lim- its, also within the pack ice between 88°-89° N. The sources of these elements at these high latitudes could be attributed to sea spray production (Cl, K, Ca, S, Br), secondary DMS-derived sulphur compounds (S), and a source of primary aerosol particles that contributed to the concentrations of the elements Si, K, Ca, Ti, Fe and Zn. This latter source has a composition which resembles that of average crustal rock. A likely transport route of minerals to the high Arctic is by way of ice-rafting by means of the Transpolar Current. These minerals originate from Siberian river runoff into the Laptev and Kara Seas. On the basis of the data available, the possibility can- not be ruled out that the minerals were first processed by the Arctic Ocean biota before becoming airborne. It appears that bubble bursting tat ejects solid particles from the sea surface micro layer or the sea water below into the atmosphere, a process that only take place in the open leads between ice floes, is a major source of pri- mary aerosol particles, which are composed of sea salt and of crustal or biogenic matter. The ice-rafting of crustal material by way of the Transpolar Current and the bubble bursting that occurs in open leads are both po- tentially sensitive to changes in climate.