An algorithm based on sea-level pressure fluctuations to identify major Baltic inflow events

Abstract

Major Baltic inflows are an important process to sustain the sensitive steady state of the Baltic Sea. We introduce an algorithm to identify atmospheric variability favourable for major Baltic inflows. The algorithm is based on sea-level pressure (SLP) fields as the only parameter. Characteristic SLP pattern fluctuations include a precursory phase of 30 days and 10 days of inflow period. The algorithm identifies successfully the majority of observed major Baltic inflows between 1961 and 2010. In addition, the algorithm finds some occurrences which cannot be related to observed inflows. In these cases with favourable atmospheric conditions, inflows were precluded by contemporaneously existing saline water masses or strong freshwater supply. Moreover, the algorithm clearly identifies the stagnation periods as a lack of SLP variability favourable for MBIs. This indicates that the lack of inflows is mainly a consequence of missing atmospheric forcing during this period. The only striking inflow which is not identified by the algorithm is the event in January 2003. We demonstrate that this is due to the special evolution of SLP fields which are not comparable with any other event. Finally, the algorithm is applied to an ensemble of scenario simulations. The result indicates that the number of atmospheric events favourable for major Baltic inflows increases slightly in all scenarios.

• major Baltic inflows
• algorithm development
• SLP variability
• Baltic Sea
• climate modeling

6. Acknowledgements

The research presented in this study is part of the Baltic Earth programme (Earth System Science for the Baltic Sea region, see http://www.baltex-research.eu/balticearth) and was funded by the Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning (FORMAS) within the projects ‘Impact of accelerated future global mean sea level rise on the phosphorus cycle in the Baltic Sea’ (Grant no. 214-2009-577) and ‘Impact of changing climate on circulation and biogeochemical cycles of the integrated North Sea and Baltic Sea system’ (Grant no. 214-2010-1575) and from Stockholm University's Strategic Marine Environmental Research Funds ‘Baltic Ecosystem Adaptive Management’ (BEAM). Additional support came from the Norden Top-level Research Initiative sub-programme ‘Effect Studies and Adaptation to Climate Change’ through the ‘Nordic Centre for Research on Marine Ecosystems and Resources under Climate Change’ (NorMER). The scenario simulations used in this study have been funded by the ‘Impacts of Climate Change on Waterways and Navigation’ KLIWAS program. KLIWAS is a joint research program of the German Federal Institute of Hydrology (BfG), the German Federal Waterways and Engineering and Research Institute (BAW), the National Weather Service of Germany (DWD) and the Federal Maritime and Hydrographic Agency (BSH) in co-operation with universities and other research institutions. KLIWAS is funded by the Federal Ministry of Transport, Building and Urban Development (BMVBS). The simulations have been conducted on the Linux clusters Krypton and Triolith, both operated by the National Supercomputer Centre in Sweden (NSC). Resources on Triolith have been made available by the Grant SNIC 002/12-25 ‘Regional climate modelling for the North Sea and Baltic Sea regions’ provided by the Swedish National infrastructure for Computing (SNIC). Salinity data used in this paper are collected from the SMHI data base SHARK (Svenskt HavsARKiv, see http://www.smhi.se/oceanografi/oce_info_data/SODC/overview.htm). Data have been collected within the coordinated Swedish environmental monitoring program by SMHI, UMF and SMF.