Topography, Hydrography, Circulation and Modelling of the Baltic Sea

Myrberg, Kai; Lehmann, Andreas

doi:10.1007/978-3-319-00440-2_2

Cited by 8 publications

(8 citation statements)

References 38 publications

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“…The thermocline was found at 15‐ to 25‐m depth across most of the Baltic Sea during the cruises except in the northern Belt Seas where it was located at 40 m (P2 and Anholt; Figure S4; Myrberg & Lehmann, ). The halocline was at 40‐ to 80‐m depth and strongest in the Baltic Proper where the deep poorly ventilated areas are located (Figure ; Myrberg & Lehmann, ). In the Baltic Proper, a redoxcline was observed below the halocline at about half the stations (red and purple stations in Figure ).…”

Section: Resultsmentioning

confidence: 99%

“…The Baltic Sea is a shallow (~50 m on average) sea with some poorly ventilated deep areas (12% has a depth > 100 m; Figure ; Myrberg & Lehmann, ). Similar to other coastal systems, it receives a high freshwater input from runoff (yearly runoff equals 2–3% of the total Baltic Sea water reservoir; D. Hansson, Eriksson, et al, ; Myrberg & Lehmann, ). Runoff typically carries excess nutrients and organic matter (OM) from agricultural impacted soils and sewage treatment facilities to coastal ecosystems.…”

Section: Introductionmentioning

confidence: 99%

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Deciphering the Role of Water Column Redoxclines on Methylmercury Cycling Using Speciation Modeling and Observations From the Baltic Sea

Soerensen

Schartup

Skrobonja

et al. 2018

Global Biogeochemical Cycles

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Oxygen‐depleted areas are spreading in coastal and offshore waters worldwide, but the implication for production and bioaccumulation of neurotoxic methylmercury (MeHg) is uncertain. We combined observations from six cruises in the Baltic Sea with speciation modeling and incubation experiments to gain insights into mercury (Hg) dynamics in oxygen depleted systems. We then developed a conceptual model describing the main drivers of Hg speciation, fluxes, and transformations in water columns with steep redox gradients. MeHg concentrations were 2–6 and 30–55 times higher in hypoxic and anoxic than in normoxic water, respectively, while only 1–3 and 1–2 times higher for total Hg (THg). We systematically detected divalent inorganic Hg (HgII) methylation in anoxic water but rarely in other waters. In anoxic water, high concentrations of dissolved sulfide cause formation of dissolved species of HgII: HgS2H−(aq) and Hg (SH)20(aq). This prolongs the lifetime and increases the reservoir of HgII readily available for methylation, driving the high MeHg concentrations in anoxic zones. In the hypoxic zone and at the hypoxic‐anoxic interface, Hg concentrations, partitioning, and speciation are all highly dynamic due to processes linked to the iron and sulfur cycles. This causes a large variability in bioavailability of Hg, and thereby MeHg concentrations, in these zones. We find that zooplankton in the summertime are exposed to 2–6 times higher MeHg concentrations in hypoxic than in normoxic water. The current spread of hypoxic zones in coastal systems worldwide could thus cause an increase in the MeHg exposure of food webs.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Deciphering the Role of Water Column Redoxclines on Methylmercury Cycling Using Speciation Modeling and Observations From the Baltic Sea

Soerensen

Schartup

Skrobonja

et al. 2018

Global Biogeochemical Cycles

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“…). The elongated ridges and the channels do not reflect the present‐day hydrographical conditions in southern Kattegat (Myrberg & Lehmann ); instead the bathymetry represents a palaeo‐river mouth in a coastal setting where the coast prograded towards the north (Figs , ). The well‐preserved palaeogeography is key to understanding the development of the area between the Great Belt valley and the southern Kattegat basin, in combination with interpretations of the seismic profiles, the vibrocores and the age determinations.…”

Section: Results and Interpretationmentioning

confidence: 99%

The Holocene Great Belt connection to the southern Kattegat, Scandinavia: Ancylus Lake drainage and Early Littorina Sea transgression

Bendixen

Jensen

Boldreel

et al. 2015

Boreas

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Late-and postglacial geological evolution of the southern Kattegat connection to the Great Belt was investigated from high-resolution seismic data and radiocarbon-dated sediment cores in order to elucidate the Ancylus Lake drainage/Littorina Sea transgression. It was found that glacial deposits form the acoustic basement and are covered by Lateglacial (LG) marine sediments and postglacial (PG; Holocene) material. The LG deposits form a highstand systems tract, whereas the PG deposits cover a full depositional sequence, consisting of a lowstand systems tract (PG I), transgressive systems tract (PG II; subdivided into three parasequences) and finally a highstand systems tract (PG III). PG I sand deposits (11.7-10.8 cal. ka BP) are found in a major western channel and in a secondary eastern channel. PG II (10.8-9.8 cal. ka BP) consists of estuarine and coastal deposits linked to an estuary located at the mouth of the channels. Both channels drained fresh water from south to north. The PG III, that is younger than 9.8 cal. ka BP, represents the threshold marine flooding at the southeastern branch of the palaeo-Great Belt channel. At 9.3 cal. ka BP, fully marine conditions were established, shortly before the flooding of the threshold to the northern part of the Great Belt. These early Holocene spits and sand bars are preserved as features on the present seabed, probably as a result of the rapid sea-level rise that led to back-stepping of the early Holocene palaeo-coast system. This study shows no evidence of major erosion or delta deposition linked to the emptying of the Ancylus Lake, which suggests that continuous water flow from the south characterized the area, without any major drainage event of the Ancylus Lake impacting the southwestern Kattegat.

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“…In April, this might be attributed to the fact that the background water temperature is relatively low during this month, T = 6 • C (see, e.g., Figure 4 in the literature [27]), and, hence, the SST contrast between the ambient and upwelled waters is not well pronounced in the satellite data. A possible reason for missing CU events in September might be a deepening of the mixed layer as a result of the thermal convection and turbulent mixing during autumn [40], making it difficult to distinguish low intensity upwelling events in IR SST data. The last and most important reason is a relatively small number of cloud-free satellite data during these months (see Figure 2).…”

Section: Satellite Observations Vs Coastal Measurementsmentioning

confidence: 99%

Remote Sensing of Coastal Upwelling in the South-Eastern Baltic Sea: Statistical Properties and Implications for the Coastal Environment

et al. 2018

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A detailed study of wind-induced coastal upwelling (CU) in the south-eastern Baltic Sea is presented based on an analysis of multi-mission satellite data. Analysis of moderate resolution imaging spectroradiometer (MODIS) sea surface temperature (SST) maps acquired between April and September of 2000-2015 allowed for the identification of 69 CU events. The Ekman-based upwelling index (UI) was applied to evaluate the effectiveness of the satellite measurements for upwelling detection. It was found that satellite data enable the identification of 87% of UI-based upwelling events during May-August, hence, serving as an effective tool for CU detection in the Baltic Sea under relatively cloud-free summer conditions. It was also shown that upwelling-induced SST drops, and its spatial properties are larger than previously registered. During extreme upwelling events, an SST drop might reach 14 • C, covering a total area of nearly 16,000 km 2 . The evolution of an upwelling front during such intensive events is accompanied by the generation of transverse filaments extending up to 70 km offshore. An analysis of the satellite optical data shows a clear decline in the chlorophyll-a concentration in the coastal zone and in the shallow Curonian Lagoon, where it drops down by an order of magnitude. It was also shown that a cold upwelling front alters the stratification in the atmospheric boundary layer, leading to a sudden drop of air temperature and near-surface winds.upwelling fronts also importantly modifies the vertical stratification and turbulent regime in the marine-atmosphere boundary layer (MABL), resulting in a change in the surface wind stress and direction in the coastal zone [3,9].Nutrient-rich waters brought up from deeper layers to the surface, particularly in the summer time, and the exposure of upwelled phytoplankton to surface radiation enhances the primary production and phytoplankton biomass during upwelling events [10,11], hence influencing the coastal pelagic communities and higher trophic levels [12]. Moreover, upwelling-related coastal ocean dynamics may eventually modify the spatial patterns of background algae blooms in the coastal zone by transporting them farther offshore.During the summer-time holiday season, CU might also have a negative impact on particular tourist areas as a result of a rapid drop in water and air temperatures near the shore [2]. Furthermore, bathing tourism depends on good water quality, while post-upwelling phytoplankton blooms might significantly reduce it, making coastal waters unattractive for recreation [13].The need to study coastal upwelling in the Baltic Sea is also essential in order to assess the regional variability of water and energy exchange, salinity dynamics, and the response of marine ecosystems to extreme events-some of the "Grand Challenges" of the Baltic Earth Science Plan [14], established in 2016. Thus, the upwelling phenomenon is indeed of certain interest to researchers, fishermen, and coastal managers [15]. The availability of wide spatial and temporal co...

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Topography, Hydrography, Circulation and Modelling of the Baltic Sea

Cited by 8 publications

References 38 publications

Deciphering the Role of Water Column Redoxclines on Methylmercury Cycling Using Speciation Modeling and Observations From the Baltic Sea

Deciphering the Role of Water Column Redoxclines on Methylmercury Cycling Using Speciation Modeling and Observations From the Baltic Sea

The Holocene Great Belt connection to the southern Kattegat, Scandinavia: Ancylus Lake drainage and Early Littorina Sea transgression

Remote Sensing of Coastal Upwelling in the South-Eastern Baltic Sea: Statistical Properties and Implications for the Coastal Environment

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