Mean cover and frequencies of vascular plant species during three decades around Abisko Scientific Research Station

Plant species distributions are expected to shift and diversity is expected to decline as a result of global climate change, particularly in the Arctic where climate warming is amplified. We have recorded the changes in richness and abundance of vascular plants at Abisko, sub-Arctic Sweden, by re-sampling five studies consisting of seven datasets; one in the mountain birch forest and six at open sites. The oldest study was initiated in 1977-1979 and the latest in 1992. Total species number increased at all sites except for the birch forest site where richness decreased. We found no general pattern in how composition of vascular plants has changed over time. Three species, Calamagrostis lapponica, Carex vaginata and Salix reticulata, showed an overall increase in cover/frequency, while two Equisetum taxa decreased. Instead, we showed that the magnitude and direction of changes in species richness and composition differ among sites.

Mean snow accumulation rate, and mean methane sulfonate, chloride and nitrate concentration in snow pits and firn cores of Dronning Maud Land

We quantified postdepositional losses of methane sulfonate (MSA-), nitrate, and chloride at the European Project for Ice Coring in Antarctica (EPICA) drilling site in Dronning Maud Land (DML) (75°S, 0°E). Analyses of four intermediate deep firn cores and 13 snow pits were considered. We found that about 26 ± 13% of the once deposited nitrate and typically 51 ± 20% of MSA- were lost, while for chloride, no significant depletion could be observed in firn older than one year. Assuming a first order exponential decay rate, the characteristic e-folding time for MSA- is 6.4 ± 3 years and 19 ± 6 years for nitrate. It turns out that for nitrate and MSA- the typical mean concentrations representative for the last 100 years were reached after 5.4 and 6.5 years, respectively, indicating that beneath a depth of around 1.2-1.4 m postdepositional losses can be neglected. In the area of investigation, only MSA- concentrations and postdepositional losses showed a distinct dependence on snow accumulation rate. Consequently, MSA- concentrations archived at this site should be significantly dependent on the variability of annual snow accumulation, and we recommend a corresponding correction. With a simple approach, we estimated the partial pressure of the free acids MSA, HNO3, and HCl on the basis of Henry's law assuming that ionic impurities of the bulk ice matrix are localized in a quasi-brine layer (QBL). In contrast to measurements, this approach predicts a nearly complete loss of MSA-, NO3 - , and Cl-.