Baltic Sea climate: 200 yr of data on air temperature, sea level variation, ice cover, and atmospheric circulation

Abstract

Relevant observed time series for the Baltic Sea region from the last 2 centuries were used to investigate climate variations and trends. These time series were: Stockholm air temperature and magnitude of seasonal temperature cycle, Stockholm sea level data, Baltic Sea maximum ice cover, and circulation types based on regional air pressure data. The definition of climate was analysed by considering how each parameter varies with the time scale. We found that 90% of the variance was for time scales shorter than 15 yr, the period then used as the climate-averaging time for all studied parameters. The results indicate positive trends for air temperature, sea level, and frequencies of anti-cyclonic circulation and westerly wind types over the last 200 yr. Negative trends were found for the magnitude of seasonal temperature cycle, sea-ice cover, and frequency of southwesterly wind. The major climate changes of the late 19th century were probably associated with the end of the 'Little Ice Age' and characterized by an unusual high frequency of cyclonic circulation. In the 20th century, pronounced positive trends were observed in sea level variation and anti-cyclonic circulation. In the most recent studied climate period (1985)(1986)(1987)(1988)(1989)(1990)(1991)(1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000), air temperature and sea level climate anomalies were positive and lay outside the range of last 200 yr normal variations. The study indicates that increased frequencies of anti-cyclonic circulation and westerly winds have resulted in a slightly warmer climate with reduced seasonal amplitude and reduced ice cover. Thereby, we support the hypothesis that the long-term climate change in the Baltic Sea region is at least partly related to changes in the atmospheric circulation.KEY WORDS: Baltic Sea · Climate · Atmospheric circulation · Temperature · Ice and sea levels Resale or republication not permitted without written consent of the publisherClim Res 25: [205][206][207][208][209][210][211][212][213][214][215][216] 2004 current climate (Heino et al. 1999, Crowley 2000, IPCC 2001, and some authors claim that warming since 1975 is likely to be partly due to increased amounts of greenhouse gases (Karlén et al. 1999, IPCC 2001. Similar warming may also have happened during the Medieval Warm Period (Crowley & Lowery 1999). Recent research using tree-ring-based chronologies indicates that the variability of recent decades may lies within the natural range (Esper at al. 2002). This illustrates the difficulty of climate research. Also, probability views based on studies using general circulation models (GCMs) may be questionable, as they often only resolve atmospheric circulation coarsely and exclude realistic treatment of some forcing mechanisms (Räisänen & Alexandersson 2003).It is often difficult to attribute a given change to a particular mechanism, and equally difficult to distinguish between trends and oscillations. It is, for example, an oversimplification to explain observed hemisphere mean surf...

Recent Change—Atmosphere

“…This is consistent with the observed upward trend in the NAO index (Hurrell and Folland 2002) and circulation changes as reported by Jacobeit et al (2003). Eriksson et al (2007) and Eriksson (2009) extended the analysis of Omstedt et al (2004) by examining the covariability of long time series from the Baltic Sea region over different timescales during boreal winter. Over a period of 500 years, 15 periods with a clearly distinct climatic signature with respect to circulation patterns, inter-annual variability and the severity of winters were identified (see Chap.…”

“…As the discrepancy in 20CR compared to other reconstructions reduces in parallel to the increase in number of stations, increasing storminess with time could be an artefact due to the changing station density (Krueger et al 2013) (Higgins 1933) and severe storm analysis by Lamb and Frydendahl (1991). Furthermore, Omstedt et al (2004) found an unusually high frequency of cyclonic circulation at the end of the nineteenth century with a pronounced peak in cyclonic weather types in 1871-1885 relative to 1800-2000. According to historical weather records of gale days for Scotland, remarkably high values were recorded for 1884-1900 (Dawson et al 2002) which contrasts with very low storm activity in the 1880s derived from the 20CR model data.…”

“…Vial and Osborn (2012) discussed the poor performance of models with respect to simulating number, frequency and spatial extent of blocking situations, a problem that had persisted for many years (d 'Andrea et al 1998). Rimbu and Lohmann (2011) used south-western Greenland temperature measurements and stable isotope records from ice cores as a proxy for North Atlantic atmospheric blocking and found that in winter, warm (cold) conditions over south-western Greenland were related to high (low) 1800-1815, 1811-1825, 1826-1840…, 1961-1975, 1976-1990, 1986-2000(Omstedt et al 2004) Fig. 4.6 The 500 hPa height field on 6 March 1948, showing a typical blocking situation (Barriopedro et al 2006) blocking activity and a negative (positive) phase of the NAO.…”

“…Their studies concluded that long-term (multi-decadal) climate change in the Baltic Sea region is at least partly related to changes in atmospheric circulation. Omstedt et al (2004) made a thorough investigation of the past 200 years of climate variability and changes based on the long Stockholm time series of temperature and sea level as well as ice cover and circulation types based on pressure data ( Fig. 4.5; see also Chap.…”

A Multivariate Baltic Sea Environmental Index

“…A similar result has been obtained by Omstedt et al (2004). They argued that it is rather problematic to clearly define 'trends' or 'regime shifts' on shorter time scales because the Baltic Sea has decadal climate modes on the order of 30-60 years.…”