Understanding past and future sea surface temperature trends in the Baltic Sea

Dutheil, Cyril; Meier, H. E. Markus; Gröger, Matthias; Börgel, Florian

doi:10.1007/s00382-021-06084-1

Cited by 33 publications

(32 citation statements)

References 43 publications

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“…The main driver of annual mean water temperature variations and long-term changes is air temperature (Meier et al, 2019c, d;Kniebusch et al, 2019a;Dutheil et al, 2021). The Baltic Sea water temperature has risen the fastest at the sea surface (Meier et al, 2022).…”

Section: 25(1) Water Temperaturementioning

confidence: 99%

“…Even higher warming of + 2-6 • C (the range denotes RCP2.6 and RCP8.5 scenarios) is projected for the Curonian Lagoon by the year 2100 (Jakimavičius et al, 2018). The north-south gradient and pronounced seasonality of SST trends would be reduced in the future due to vanishing sea ice (Dutheil et al, 2021).…”

Section: 35(1) Water Temperaturementioning

confidence: 99%

“…However, only a few studies of their impacts on the marine ecosystem exist. Furthermore, SST trends also depend on coastal upwelling, which affects large areas of the Baltic Sea surface (Lehmann et al, 2012;Dutheil et al, 2021). Projected changes in upwelling are, however, very uncertain (Meier et al, 2022).…”

Section: Water Temperaturementioning

confidence: 99%

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Climate change in the Baltic Sea region: a summary

et al. 2022

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Abstract. Based on the Baltic Earth Assessment Reports of this thematic issue in Earth System Dynamics and recent peer-reviewed literature, current knowledge of the effects of global warming on past and future changes in climate of the Baltic Sea region is summarised and assessed. The study is an update of the Second Assessment of Climate Change (BACC II) published in 2015 and focuses on the atmosphere, land, cryosphere, ocean, sediments, and the terrestrial and marine biosphere. Based on the summaries of the recent knowledge gained in palaeo-, historical, and future regional climate research, we find that the main conclusions from earlier assessments still remain valid. However, new long-term, homogenous observational records, for example, for Scandinavian glacier inventories, sea-level-driven saltwater inflows, so-called Major Baltic Inflows, and phytoplankton species distribution, and new scenario simulations with improved models, for example, for glaciers, lake ice, and marine food web, have become available. In many cases, uncertainties can now be better estimated than before because more models were included in the ensembles, especially for the Baltic Sea. With the help of coupled models, feedbacks between several components of the Earth system have been studied, and multiple driver studies were performed, e.g. projections of the food web that include fisheries, eutrophication, and climate change. New datasets and projections have led to a revised understanding of changes in some variables such as salinity. Furthermore, it has become evident that natural variability, in particular for the ocean on multidecadal timescales, is greater than previously estimated, challenging our ability to detect observed and projected changes in climate. In this context, the first palaeoclimate simulations regionalised for the Baltic Sea region are instructive. Hence, estimated uncertainties for the projections of many variables increased. In addition to the well-known influence of the North Atlantic Oscillation, it was found that also other low-frequency modes of internal variability, such as the Atlantic Multidecadal Variability, have profound effects on the climate of the Baltic Sea region. Challenges were also identified, such as the systematic discrepancy between future cloudiness trends in global and regional models and the difficulty of confidently attributing large observed changes in marine ecosystems to climate change. Finally, we compare our results with other coastal sea assessments, such as the North Sea Region Climate Change Assessment (NOSCCA), and find that the effects of climate change on the Baltic Sea differ from those on the North Sea, since Baltic Sea oceanography and ecosystems are very different from other coastal seas such as the North Sea. While the North Sea dynamics are dominated by tides, the Baltic Sea is characterised by brackish water, a perennial vertical stratification in the southern subbasins, and a seasonal sea ice cover in the northern subbasins.

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Section: 25(1) Water Temperaturementioning

confidence: 99%

Section: 35(1) Water Temperaturementioning

confidence: 99%

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Climate change in the Baltic Sea region: a summary

et al. 2022

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“…The thermal structure at BY2 and BY5 (Fig. 5a) reflects the well-studied cold intermediate layer (CIL, Liblik and Lips, 2019;Dutheil et al, 2021), the remnant of a water mass that formed during the previous winter at a depth between 20 and Station BY15 represents fully open sea conditions in the eastern Gotland Basin (Fig. 1b).…”

Section: Mean Seasonal Cyclementioning

confidence: 98%

The Baltic Sea model inter-comparison project BMIP – a platform for model development, evaluation, and uncertainty assessment

Gröger

Placke

Meier

et al. 2022

Preprint

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Abstract. While advanced computational capabilities have enabled the development of complex ocean general circulation models (OGCM) for marginal seas, systematic comparisons of regional ocean models and their setups are still rare. The Baltic Sea model inter-comparison project (BMIP), introduced herein, was therefore established as a platform for the scientific analysis and systematic comparison of Baltic Sea models. The inclusion of a physically consistent regional reanalysis data set for the period 1961–2018 allows standardized meteorological forcing and river runoff. Protocols to harmonize model outputs and analyses are provided as well. An analysis of six simulations performed with four regional OGCMs differing in their resolution, grid coordinates, and numerical methods was carried out to explore inter-model differences despite harmonized forcing. Uncertainties in modeled surface temperatures were shown to be larger at extreme than at moderate temperatures. In addition, a roughly linear increase in the temperature spread with increasing water depth was determined and indicated larger uncertainties in the near-bottom layer. On the seasonal scale, the model spread was larger in summer than in winter, likely due to differences in the models’ thermocline dynamics. In winter, stronger air-sea heat fluxes and vigorous convective and wind mixing reduced the inter-model spread. Uncertainties were likewise reduced near the coasts, where the impact of meteorological forcing was stronger. The uncertainties were highest in the Bothnian Sea and Bothnian Bay, attributable to the differences between the models in the seasonal cycles of sea ice triggered by the ice-albedo feedback. However, despite the large spreads in the mean climatologies, high inter-annual correlations between the sea surface temperatures (SSTs) of all models and data derived from a satellite product were determined. The exceptions were the Bothnian Sea and Bothnian Bay, where the correlation dropped significantly, likely related to the effect of sea ice on air-sea heat exchange. Marine heat waves (MHWs), coastal upwelling, and stratification were also assessed. In all models, MHWs were more frequent in shallow areas and in regions with seasonal ice cover. An increase in the frequency (regionally varying between ~50 and 250 %) and duration (50–150 %) of MHWs during the last three decades in all models was found as well. The uncertainties were highest in the Bothnian Bay, likely due to the different trends in sea-ice presence. All but one of the analyzed models overestimated upwelling frequencies along the Swedish coast, the Gulf of Finland, and around Gotland while they underestimated upwelling in the Gulf of Riga. The onset and seasonal cycle of thermal stratification likewise differed among the models. Compared to observation-based estimates, in all models the thermocline in early spring was too deep whereas a good match was obtained in June, when the thermocline intensifies.

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“…The long winter and the strong seasonal cycle give the area subarctic properties, especially in the northern areas. The Baltic Sea has also been shown to warm up faster than most other sea areas of the world (Belkin, 2009;Sherman et al, 2009), albeit with large differences between sub-basins (Kniebusch et al, 2019;Dutheil et al, 2021).The Baltic Sea is also strongly affected by its watershed, which is more than 4 times larger than its surface area and is inhabited by ca. 85 million people (Omran and Negm, 2020).…”

Section: Introductionmentioning

confidence: 99%

Global climate change and the Baltic Sea ecosystem: direct and indirect effects on species, communities and ecosystem functioning

Viitasalo

Bonsdorff

2022

Earth Syst. Dynam.

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Abstract. Climate change has multiple effects on Baltic Sea species, communities and ecosystem functioning through changes in physical and biogeochemical environmental characteristics of the sea. Associated indirect and secondary effects on species interactions, trophic dynamics and ecosystem function are expected to be significant. We review studies investigating species-, population- and ecosystem-level effects of abiotic factors that may change due to global climate change, such as temperature, salinity, oxygen, pH, nutrient levels, and the more indirect biogeochemical and food web processes, primarily based on peer-reviewed literature published since 2010. For phytoplankton, clear symptoms of climate change, such as prolongation of the growing season, are evident and can be explained by the warming, but otherwise climate effects vary from species to species and area to area. Several modelling studies project a decrease of phytoplankton bloom in spring and an increase in cyanobacteria blooms in summer. The associated increase in N:P ratio may contribute to maintaining the “vicious circle of eutrophication”. However, uncertainties remain because some field studies claim that cyanobacteria have not increased and some experimental studies show that responses of cyanobacteria to temperature, salinity and pH vary from species to species. An increase of riverine dissolved organic matter (DOM) may also decrease primary production, but the relative importance of this process in different sea areas is not well known. Bacteria growth is favoured by increasing temperature and DOM, but complex effects in the microbial food web are probable. Warming of seawater in spring also speeds up zooplankton growth and shortens the time lag between phytoplankton and zooplankton peaks, which may lead to decreasing of phytoplankton in spring. In summer, a shift towards smaller-sized zooplankton and a decline of marine copepod species has been projected. In deep benthic communities, continued eutrophication promotes high sedimentation and maintains good food conditions for zoobenthos. If nutrient abatement proceeds, improving oxygen conditions will first increase zoobenthos biomass, but the subsequent decrease of sedimenting matter will disrupt the pelagic–benthic coupling and lead to a decreased zoobenthos biomass. In the shallower photic systems, heatwaves may produce eutrophication-like effects, e.g. overgrowth of bladderwrack by epiphytes, due to a trophic cascade. If salinity also declines, marine species such as bladderwrack, eelgrass and blue mussel may decline. Freshwater vascular plants will be favoured but they cannot replace macroalgae on rocky substrates. Consequently invertebrates and fish benefiting from macroalgal belts may also suffer. Climate-induced changes in the environment also favour establishment of non-indigenous species, potentially affecting food web dynamics in the Baltic Sea. As for fish, salinity decline and continuing of hypoxia is projected to keep cod stocks low, whereas the increasing temperature has been projected to favour sprat and certain coastal fish. Regime shifts and cascading effects have been observed in both pelagic and benthic systems as a result of several climatic and environmental effects acting synergistically. Knowledge gaps include uncertainties in projecting the future salinity level, as well as stratification and potential rate of internal loading, under different climate forcings. This weakens our ability to project how pelagic productivity, fish populations and macroalgal communities may change in the future. The 3D ecosystem models, food web models and 2D species distribution models would benefit from integration, but progress is slowed down by scale problems and inability of models to consider the complex interactions between species. Experimental work should be better integrated into empirical and modelling studies of food web dynamics to get a more comprehensive view of the responses of the pelagic and benthic systems to climate change, from bacteria to fish. In addition, to better understand the effects of climate change on the biodiversity of the Baltic Sea, more emphasis should be placed on studies of shallow photic environments. The fate of the Baltic Sea ecosystem will depend on various intertwined environmental factors and on development of the society. Climate change will probably delay the effects of nutrient abatement and tend to keep the ecosystem in its “novel” state. However, several modelling studies conclude that nutrient reductions will be a stronger driver for ecosystem functioning of the Baltic Sea than climate change. Such studies highlight the importance of studying the Baltic Sea as an interlinked socio-ecological system.

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Understanding past and future sea surface temperature trends in the Baltic Sea

Cited by 33 publications

References 43 publications

Climate change in the Baltic Sea region: a summary

Climate change in the Baltic Sea region: a summary

The Baltic Sea model inter-comparison project BMIP – a platform for model development, evaluation, and uncertainty assessment

Global climate change and the Baltic Sea ecosystem: direct and indirect effects on species, communities and ecosystem functioning

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