Detailed assessment of climate variability in the Baltic Sea area for the period 1958 to 2009

Lehmann, Andreas; Getzlaff, Klaus; Harlaß, Jan

doi:10.3354/cr00876

Cited by 184 publications

(156 citation statements)

References 31 publications

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“…Although single remote sensing images are frequently disturbed by cloud coverage, skin layer uncertainties and other factors, the monthly mean SST from the remote sensing data agree well with those from in situ measurements in the offshore sea areas (Siegel et al 2006;Bradtke et al 2010). Lehmann et al (2011) used remote sensing data for 1990-2008 to derive a linear trend of annual mean SST of up to 1°C per decade in the northern part of the Bothnian Bay, but a high increase was also found in the Gulf of Finland and Gulf of Riga and in the northern Baltic Proper (Fig. 7.2).…”

Section: Trends and Variations In Water Temperaturesupporting

confidence: 55%

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Recent Change—Marine Circulation and Stratification

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Lehmann

Myrberg

2015

Regional Climate Studies

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This chapter describes recent change in the circulation and stratification of the Baltic Sea. A recent warming trend in sea-surface waters has been clearly demonstrated by in situ measurements, remote sensing data and numerical models. Trends in sea-surface temperature (SST) for the past three to four decades based on remote sensing data generally agree with trends determined from in situ observations. Models suggest the current warming within the Baltic Sea lies within the range experienced during the past 500 years. The salinity and stratification of the deep waters are strongly linked to the major inflows of North Sea water that occur sporadically and bring high-saline water into the deep layers of the Baltic Sea. The major inflows normally occur during winter and spring and bring cold oxygen-rich waters into the deep basins. Since 1996, large inflows have also occurred during summer, bringing in warm low-oxygen water. IntroductionChanges in thermohaline characteristics and stratification of the water column are usually analysed on the basis of data from repeat hydrographic observations, originating from shipborne monitoring programmes and/or permanent coastal and offshore oceanographic stations. Such datasets are described in recent books by Feistel et al. (2008) and Leppäranta and Myrberg (2009). In situ observations are often irregular in space and time, especially for offshore areas; therefore, trends and variability in the ocean state can only be determined by careful pre-processing of the data to address issues such as data homogenisation and the suppression of aliasing errors. In recent decades, horizontal undersampling by in situ measurements has been partially offset by the remote sensing of sea-surface properties from satellites; with these data free of spatial aliasing errors due to their high horizontal resolution. Satellite-derived cloud-free products for sea-surface temperature (SST) have been reasonably accurate since the 1980s. Many of the papers published over the past decade that address trends and variability in the circulation and stratification of the Baltic Sea are based on remote sensing data, often in combination with in situ observations and the results of numerical modelling. Improvements in the physical and numerical features of the models, accompanied by model validation studies, have increased confidence in the realism of the model results. Models provide dynamically balanced gridded datasets over decades or longer, including information for 'noisy' variables such as currents, transport and mixing fluxes. This chapter analyses the recent peer-reviewed literature, extending the findings from earlier review (Box 7.1).

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Section: Trends and Variations In Water Temperaturesupporting

confidence: 55%

“…4, Box 4.1) and/or the Baltic Sea Index (BSI, difference of sea-level air pressure anomalies between Oslo and Szczecin, Lehmann et al 2002) indices (e.g. Lehmann et al 2011;Dippner et al 2012). In the northern sea areas, the recent decrease in the extent and duration of ice cover (see Chap.…”

Section: Trends and Variations In Water Temperaturementioning

confidence: 99%

Recent Change—Marine Circulation and Stratification

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Lehmann

Myrberg

2015

Regional Climate Studies

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“…Early publications, for example, by Tinz (1996), Chen and Hellström (1999), Koslowski and Glaser (1999), Jevrejeva (2001), Omstedt and Chen (2001) and Andersson (2002) agreed that there has been a north-eastward shift in low-pressure tracks, which is consistent with a more zonal circulation over the Baltic Sea basin and the observed trend of a more positive NAO index, at least up to the 1990s (Trenberth et al 2007). A northward shift in low-pressure tracks is also consistent with model projections of anthropogenic climate change, as pointed out by Leckebusch and Ulbrich (2004), Bengtsson et al (2006), Leckebusch et al (2006), Pinto et al (2007) and, more recently, Lehmann et al (2011). Jacobeit et al (2001Jacobeit et al ( , 2003 and Hurrell and Folland (2002) discussed the strong temporal variability in the relationship between the general circulation of the atmosphere and surface climate characteristics over the past 300 years.…”

Section: Long-term Circulation Changesmentioning

confidence: 51%

“…The NE shift of the NAO together with the increased pressure gradient over the North Atlantic extended the geographical influence and numbers of deep lows towards the Baltic Sea region (Fig. 4.8, Wang et al 2006;Lehmann et al 2011), explaining upward trends in annual and winter to spring storminess from the 1960s to 1990s. However, this relation depends on the region and time period (Matulla et al 2008), where recent decades show a very high influence of the NAO (Alexander et al 2005) with a weaker link in previous times (Alexandersson et al 1998).…”

Section: Long-term Trends Versus Decadal Variabilitymentioning

confidence: 99%

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Recent Change—Atmosphere

Rutgersson

Jaagus

Schenk

et al. 2015

Regional Climate Studies

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This chapter describes observed changes in atmospheric conditions in the Baltic Sea drainage basin over the past 200-300 years. The Baltic Sea area is relatively unique with a dense observational network covering an extended time period. Data analysis covers an early period with sparse and relatively uncertain measurements, a period with well-developed synoptic stations, and a final period with 30+ years of satellite data and sounding systems. The atmospheric circulation in the European/Atlantic sector has an important role in the regional climate of the Baltic Sea basin, especially the North Atlantic Oscillation. Warming has been observed, particularly in spring, and has been stronger in the northern regions. There has been a northward shift in storm tracks, as well as increased cyclonic activity in recent decades and an increased persistence of weather types. There are no long-term trends in annual wind statistics since the nineteenth century, but much variation at the (multi-)decadal timescale. There are also no long-term trends in precipitation, but an indication of longer precipitation periods and possibly an increased risk of extreme precipitation events.

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Simulated halocline variability in the Baltic Sea and its impact on hypoxia during 1961–2007

2013

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1] Salinity and halocline depth variations in the Baltic Sea during 1961-2007 are studied using a three-dimensional ocean circulation model. Significant interannual and interdecadal variations in the halocline depth are found, together with distinct periods characterized either by shallow (1970)(1971)(1972)(1973)(1974)(1975) or deep halocline (1990)(1991)(1992)(1993)(1994)(1995). The model simulation indicates that the mean top layer salinity in the Baltic Sea is mainly controlled by the accumulated river runoff, while the mean below halocline salinity in the Baltic proper (which comprises Bornholm and Gotland basins) is more dependent on the low-pass filtered zonal wind stress, with cutoff period of 4 years, henceforth called the mean zonal wind stress. The halocline depth and stratification strength in the Baltic Sea are significantly affected by the mean zonal wind stress, while the impact of runoff is smaller. The ventilation of the halocline from bottom layers is stronger during the shallow and from surface layers during the deep halocline period. Due to changes in ventilation variations in halocline depth systematically affect bottom oxygen concentrations on seasonal and decadal, but not on interannual time scales. For instance, a deeper halocline reduces hypoxic (oxygen concentration in bottom water below 2 mL/L) and anoxic (anoxic conditions in bottom water) areas and increases the bottom oxygen concentrations in the Gulf of Finland but decreases them in the deeper parts of the Baltic proper. Model results suggest that due to undersampling during 1961-2007 mean hypoxic and anoxic areas calculated from observed profiles are underestimated by 41% and 43%, respectively.

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Detailed assessment of climate variability in the Baltic Sea area for the period 1958 to 2009

Cited by 184 publications

References 31 publications

Recent Change—Marine Circulation and Stratification

Recent Change—Marine Circulation and Stratification

Recent Change—Atmosphere

Simulated halocline variability in the Baltic Sea and its impact on hypoxia during 1961–2007

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