On Regime Shifts and Budgets for Nutrients in the Open Baltic Proper: Evaluations Based on Extensive Data between 1974 and 2005

Håkanson, Lars; Lindgren, Dan

doi:10.2112/07-0870.1

Cited by 8 publications

(9 citation statements)

References 40 publications

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“…MacKenzie and Schiedek (2007a) argued that summer warming rates have almost tripled compared to those that could be expected from the observed increase in air temperature. In contrast to this and to the results of many other studies, Håkanson and Lindgren (2008) concluded, from a simple treatment of raw irregular HELCOM data , that 'there is no increase in surface-water temperatures in the Baltic Proper, but rather a weak opposite trend'. It could be that this dataset contains more observations from the cold season over recent decades and so the rising trend in SST is not visible.…”

Section: Trends and Variations In Water Temperaturecontrasting

confidence: 79%

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 Temperaturecontrasting

confidence: 79%

Recent Change—Marine Circulation and Stratification

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Lehmann

Myrberg

2015

Regional Climate Studies

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“…Low Secchi depth and intensive summer blooms of cyanobacteria have been two eutrophication signs which have been associated with elevated levels of anthropogenic nutrient loads to this large estuary. Empirical data constitute the primary foundation for all types of environmental analysis connected to causes and effects [1] and much of the pastime Baltic Sea research has therefore been directed towards detecting long-term trends in improving indicator variables. Previous studies on long-term trends highlighted eutrophication effects and their temporal variation in the Baltic Sea and have focused on, e. g., total phosphorus (TP) loadings [2], riverine TP and total nitrogen (TN) loadings [3], the Secchi depth [4], concentrations of chlorophyll-a [1,5], biomasses of phytoplankton groups [5], and TP concentrations [1].…”

Section: Introductionmentioning

confidence: 99%

“…Phosphorus is a key nutrient in the context of Baltic Sea eutrophication [1,7,9,10]. Since costly TP reductions have been undertaken extensively in most of the surrounding countries, it should be of great interest to managers and the scientific community to be able to compare how the TP loading has varied in relation to TP concentrations.…”

Section: Introductionmentioning

confidence: 99%

“…The idea is to determine long-term time trends from the 1960s or 1970s to recent years in these basins. Håkanson and Lindgren [1] presented TP trends from 1990 in the Baltic Proper only, which means that the coming analysis will be much more comprehensive. The analysis is restricted to surface waters since this is where algal blooms and other types of primary production occur.…”

Section: Introductionmentioning

confidence: 99%

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Trends in Total Phosphorus Loadings and Concentrations Regarding Surface Waters of the Baltic Sea, 1968-2007

Bryhn

2010

TOOCEAJ

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Abstract:The Baltic Sea, a large estuarine sea in northern Europe, has for many decades displayed obvious signs of anthropogenic eutrophication. This study relates long-term trends in total phosphorus (TP) loadings and TP concentrations in surface waters regarding five major sub-basins of the Baltic Sea; the Bothnian Bay, the Bothnian Sea, the Baltic Proper, the Gulf of Finland and the Gulf of Riga. The longest time series ever published on these variables was developed and used for this purpose. TP loadings to these waters have decreased greatly and significantly since the 1980s. However, TP concentrations have only decreased slightly in one of the sub-basins while concentrations have increased in the other four basins. Four possible hypotheses about the weak connection between TP loadings and concentrations are 1) increasing TP concentration is a delayed effect from many decades of intensive TP loading, 2) fewer saline inflows of high intensity have decreased sedimentation rates and increased TP concentrations, 3) fewer oxygen-rich saline inflows of high intensity have increased TP diffusion from deep sediments to the whole water column and 4) less ice in the winter has increased the erosion and resuspension of shallow sediments and increased TP concentrations.

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“…Regime shifts have been observed in many oceans and seas like the North Pacific (Chiba et al 2008;Hare and Mantua 2000), the Atlantic (Beaugrand 2004a), the Baltic (Hakanson and Lindgren 2008), the North Sea (Edwards et al 2002;McQuatters-Gollop et al 2007;Weijerman et al 2005), as well as in many lakes (Scheffer et al 2001). These regime shifts are often driven by changes in large-scale weather patterns like the Pacific decadal oscillation or the North Atlantic Oscillation (NAO).…”

Section: Introductionmentioning

confidence: 99%

Changes in Phytoplankton Biomass in the Western Scheldt Estuary During the Period 1978–2006

Kromkamp

Engeland

2009

Estuaries and Coasts

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We investigated whether climate change results in long-term changes in phytoplankton biomass and phenology in a turbid eutrophic coastal plain estuary. Changes in annual mean chlorophyll a (chla) concentrations were studied for the period 1978-2006 in the eutrophic and turbid macro-tidal Western Scheldt estuary. Three stations were investigated: WS1, at the mouth of the estuary; station WS6, halfway up the estuary; and station WS11, near the Dutch-Belgian border near the upstream end of the estuary. No significant long-term changes in yearly averaged chla concentrations were observed in WS1 and WS6, but in WS11 the phytoplankton biomass decreased considerably. This is most likely due to an increase in grazing pressure as a result of an improvement in the dissolved oxygen concentrations. Spectral analyses revealed a possible periodicity of 7 years in the mean chla which was related to periodicity in river discharge. We also observed strong phenological responses in the timing of the spring/summer bloom which were related to a welldocumented increase in the temperature in the estuary. The fulcrum, the center of gravity or the day at which 50% of the cumulative chla was reached during the year, advanced by 1-2 days/year. A similar trend was observed for the month in which the maximum bloom was observed, with the exception of station WS1. All stations showed an earlier initiation of the bloom, whereas the day at which the phytoplankton bloom was terminated also moved forward in time excepted for WS11. As a result, the bloom length decreased at station WS1, remained the same at station WS6, and increased at WS11. This complicated pattern in bloom phenology demonstrates the complex nature of ecosystem functioning in estuaries.

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On Regime Shifts and Budgets for Nutrients in the Open Baltic Proper: Evaluations Based on Extensive Data between 1974 and 2005

Cited by 8 publications

References 40 publications

Recent Change—Marine Circulation and Stratification

Recent Change—Marine Circulation and Stratification

Trends in Total Phosphorus Loadings and Concentrations Regarding Surface Waters of the Baltic Sea, 1968-2007

Changes in Phytoplankton Biomass in the Western Scheldt Estuary During the Period 1978–2006

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