Influence of sea level rise on the dynamics of salt inflows in the Baltic Sea

The Baltic Sea is a marginal sea, located in a highly industrialized region in Central Northern Europe. Saltwater inflows from the North Sea and associated ventilation of the deep exert crucial control on the entire Baltic Sea ecosystem. This study explores the impact of anticipated sea level changes on the dynamics of those inflows. We use a numerical oceanic general circulation model covering both the Baltic and the North Sea. The model successfully retraces the essential ventilation dynamics throughout the period 1961–2007. A suite of idealized experiments suggests that rising sea level is associated with intensified ventilation as saltwater inflows become stronger, longer, and more frequent. Expressed quantitatively as a salinity increase in the deep central Baltic Sea, we find that a sea level rise of 1 m triggers a saltening of more than 1 PSU. This substantial increase in ventilation is the consequence of the increasing cross section in the Danish Straits amplified by a reduction of vertical mixin

The Baltic Sea Tracer Release Experiment. Part I: Mixing rates

In this study, results from the Baltic Sea Tracer Release Experiment (BATRE) are described, in which deep water mixing rates and mixing processes in the central Baltic Sea were investigated. In September 2007, an inert tracer gas (CF3SF5) was injected at approximately 200 m depth in the Gotland Basin, and the subsequent spreading of the tracer was observed during six surveys until February 2009. These data describe the diapycnal and lateral mixing during a stagnation period without any significant deep water renewal due to inflow events. As one of the main results, vertical mixing rates were found to dramatically increase after the tracer had reached the lateral boundaries of the basin, suggesting boundary mixing as the key process for basin-scale vertical mixing. Basin-scale vertical diffusivities were of the order of 10−5 m2 s−1 (about 1 order of magnitude larger than interior diffusivities) with evidence for a seasonal and vertical variability. In contrast to tracer experiments in the open ocean, the basin geometry (hypsography) was found to have a crucial impact on the vertical tracer spreading. The e-folding time scale for deep water renewal due to mixing was slightly less than 2 years, the time scale for the lateral homogenization of the tracer patch was of the order of a few months. Key Points: Mixing rates in the Gotland Basin are dominated by boundary mixing processes; The time scale for Gotland Basin deep water renewal is approximately 2 years; Mixing rates determined from the tracer CF3SF

The Copernicus Marine Environment Monitoring Service Ocean State Report

The Copernicus Marine Environment Monitoring Service (CMEMS) Ocean State Report (OSR) provides an annual report of the state of the global ocean and European regional seas for policy and decision-makers with the additional aim of increasing general public awareness about the status of, and changes in, the marine environment. The CMEMS OSR draws on expert analysis and provides a 3-D view (through reanalysis systems), a view from above (through remote-sensing data) and a direct view of the interior (through in situ measurements) of the global ocean and the European regional seas. The report is based on the unique CMEMS monitoring capabilities of the blue (hydrography, currents), white (sea ice) and green (e.g. Chlorophyll) marine environment. This first issue of the CMEMS OSR provides guidance on Essential Variables, large-scale changes and specific events related to the physical ocean state over the period 1993–2015. Principal findings of this first CMEMS OSR show a significant increase in global and regional sea levels, thermosteric expansion, ocean heat content, sea surface temperature and Antarctic sea ice extent and conversely a decrease in Arctic sea ice extent during the 1993–2015 period. During the year 2015 exceptionally strong large-scale changes were monitored such as, for example, a strong El Niño Southern Oscillation, a high frequency of extreme storms and sea level events in specific regions in addition to areas of high sea level and harmful algae blooms. At the same time, some areas in the Arctic Ocean experienced exceptionally low sea ice extent and temperatures below average were observed in the North Atlantic Ocean

BSRA-15: A Baltic Sea Reanalysis 1990–2004

Oceanographic observations are often of high quality but are available only with low resolution in time and space. On the other hand, model fields have high resolution in time and space but are not necessarily in agreement with observations. To bridge the gap between these very different kinds of data sets, a reanalysis can be made, which means that fixed versions of the numerical model and the data assimilation system are used to analyse a period of several years. This report describes an oceanographic reanalysis covering the period 1990 to 2004 (15 whole years). The horizontal resolution is 3 nautical miles in the Baltic Sea and 12 nautical miles in the North Sea, and the vertical resolution varies between 4 meters near the surface to 60 meters in the deepest part (up to 24 vertical layers). The time resolution of the reanalysis product is 6 hours. The numerical ocean model used is HIROMB (High-Resolution Operational Model for the Baltic), version 3.0. The data assimilation method used in this reanalysis is the Successive Corrections Method (SCM) for salinity and temperature, whereas ice observations in terms of ice charts were simply interpolated. The result looks good in terms of sea levels, ice fields, and salinity and temperature structure, whereas currents have not been validated. This oceanographic reanalysis was probably the first one ever for the Baltic Sea (when it was done in 2005) and may serve as a starting point before longer, more advanced reanalyses are produced

Fourth Workshop on Baltic Sea Ice Climate. Norrköping, Sweden 22-24 May, 2002. Conference Proceedings

The Baltic Sea ice is strongly influenced by the atmospheric circulation and  shows large interannual variability. At the same time the Baltic Sea is one of the most investigated regions on earth with long ice time series. To detect trends in climate change and to relate these to natural or anthropogenic causes are of central importance in the present Baltic Sea research. This was also the main topic during the Fourth Workshop on Baltic Sea Ice Climate held in Norrköping, 22-24 May, 2002. The workshop was organised by SMHI, the SWECLIM program, the Department of Oceanography at the Earth Sciences Centre of Göteborg University, and the Swedish Maritime Administration

Modeling the seasonal, interannual, and long-term variations of salinity and temperature in the Baltic proper

Salinity and temperature variations in the Baltic proper and the Kattegat have been analyzed with a numerical ocean model and a large amount of observational data. In the model, the Baltic Sea is divided into 13 sub-basins with high vertical resolution, horizontally coupled by barotropic and baroclinic flows and vertically coupled to a sea-ice model which includes dynamics as well as thermodynamics. The model was integrated for a 15-year period (1980-1995) by using observed meteorological forcing data, river-runoff data and sea-level data from the Kattegat. The calculated 15-year median profiles of salinity and temperature in the different sub-basins are in good agreement with observations. However, the calculated mid-depth salinities in the Arkona Basin and Bornholm Basin were somewhat overestimated, and the calculated deep-water temperatures in the Arkona Basin and the Bornholm Basin are somewhat lower than the observed values. Frontal mixing and movements in the Kattegat and the entrance area of the Arkona Basin were important to consider in the model. Water masses were simulated well, and prescribing constant deep-water properties in the Kattegat proved to be a reasonable lateral boundary condition. Further, comparisons were made between observed and calculated seasonal and interannual variations of the hydrographic properties in the Eastern Gotland Basin, as well as the interannual variations of the annual maximum ice extent. We conclude that the model can simulate these variations realistically. The major Baltic inflow of 1993 was also simulated by the model, but the inflowing water was 1-2 degrees degrees too cold. Finally, the response times to changes in forcing of the Baltic proper and the Kattegat were investigated by performing the so-called lock-exchange experiment. Typical stratification spin-up times were of the order of 10 years for the Kattegat, and 100 years for the Baltic proper

Ice and AIS : ship speed data and sea ice forecasts in the Baltic Sea

The Baltic Sea is a seasonally ice-covered marginal sea located in a densely populated area in northern Europe. Severe sea ice conditions have the potential to hinder the intense ship traffic considerably. Thus, sea ice fore-and nowcasts are regularly provided by the national weather services. Typically, the forecast comprises several ice properties that are distributed as prognostic variables, but their actual usefulness is difficult to measure, and the ship captains must determine their relative importance and relevance for optimal ship speed and safety ad hoc. The present study provides a more objective approach by comparing the ship speeds, obtained by the automatic identification system (AIS), with the respective forecasted ice conditions. We find that, despite an unavoidable random component, this information is useful to constrain and rate fore-and nowcasts. More precisely, 62-67% of ship speed variations can be explained by the forecasted ice properties when fitting a mixed-effect model. This statistical fit is based on a test region in the Bothnian Sea during the severe winter 2011 and employs 15 to 25 min averages of ship speed

Teacher Students’ Critical Thinking Skills Using the Concept of Disruptive Technologies

Critical thinking is fundamental to 21st century learning and has thus become an important part of the technology curricula in many countries. Critical thinking draws on the ability to examine, analyse, interpret and evaluate, as well as asking questions and participating in discussions about risks and benefits of different technological solutions. An important task for teachers is to support young children in developing these skills. Students on a Swedish primary school teacher education programme were given an assignment inspired by the concept of ‘disruptive technologies’ (Barlex, Givens & Steeg, 2016; Manyika, Chui, Bughin, Dobbs, Bisson & Marrs, 2013), choosing from one of nine disruptive technologies and searching for information. The list was created on the grounds that these are technologies that are likely to have a significant effect on the students’ lives in a not too distant future. Based on the information found, the students were to critically analyse the technology they had chosen. This case study was performed through a thematic analysis of 120 assignment texts. The analysis showed that some of the suggested technologies were chosen more often than others. Autonomous cars came top, although robots in elderly care were the most frequently chosen technology among female students. The students performed well in the searching and collecting process. They found information about pros and cons for their chosen disruptive technology. However, the analysis also showed that the students had difficulty evaluating and problematising the information they had found. In their conclusions they did not change their original point of view. Even though they found more negative aspects of a new technology, they accentuated the positives