Assessment of extreme hydrological conditions in the Bothnian Bay, Baltic Sea, and the impact of the nuclear power plant “Hanhikivi-1” on the local thermal regime

Abstract

Abstract. The results of the study aimed to assess the influence of future nuclear power plant "Hanhikivi-1" upon the local thermal conditions in the Bothnian Bay in the Baltic Sea are presented. A number of experiments with different numerical models were also carried out in order to estimate the extreme hydro-meteorological conditions in the area of the construction. The numerical experiments were fulfilled both with analytically specified external forcing and with real external forcing for 2 years: a cold year (2010) and a warm year (2014). The study has shown that the extreme values of sea level and water temperature and the characteristics of wind waves and sea ice in the vicinity of the future nuclear power plant can be significant and sometimes catastrophic. Permanent release of heat into the marine environment from an operating nuclear power plant will lead to a strong increase in temperature and the disappearance of ice cover within a 2 km vicinity of the station. These effects should be taken into account when assessing local climate changes in the future.

Modeling of Sediment Transport in Bothnian Bay in the Vicinity of the Nuclear Power Plant ‘Hanhikivi-1’ Construction Site

“…In this work we used a coupled modeling system ( Figure 1) previously developed in [21] to (assess 1) possible extreme hydrometeorological conditions in the area of the 'Hanhikivi-1' NPP construction site ( Figure 2), and (2) the impact of the potential NPP's thermal effects on the hydrological conditions in the Hanhikivi area. The results obtained showed that the model reproduced the main features of dynamical properties and thermohaline structure and wind waves pattern which was demonstrated in detail in [21] by comparison with operational model HIROMB (High Resolution Operational Model for the Baltic Sea) and observations at stations located in Bothnian Bay.…”

“…The use of the sigma-based Princeton Ocean Model for the current study was dictated by the need to make, in addition to the lithodynamics modeling, a complex assessment of the hydrological conditions in the shallow Hanhikivi area, including the extreme maximum and minimum water levels [21]. For this kind of work, the z-based models are hardly applicable due to the possible problems associated with very low sea level events when the sea level decrease becomes larger than the thickness of the upper grid layer.…”

“…The correspondence of the wave field and ice-free region is clear. A choice of 0.5-isoline of sea ice concentration as the ice edge made it possible to maximally match the results of field measurements of wave height in the vicinity of the Hanhikivi cape [21]. There is no doubt that such a simple parameterization is a fairly rough approximation of the wave processes occurring in the marginal ice zone, but as a first approximation it allows taking into account the presence of ice cover in the other parts of Bothnian Bay and its influence upon the wind waves field in the Hanhikivi model domain.…”

“…A number of recent studies were focused on the risk assessment of external events (e.g., [17,18]), the NPP's severe accident calculation [19], possible impacts of the NPP to the Bothnian Bay fauna [20] and on modeling of hydrological conditions [21] in the area of the Hanhikivi peninsula. In [22] the frequencies of frazil ice and algae in the Gulf of Bothnian (with conditions similar to that of Hanhikivi) were investigated since these two phenomena can affect the NPP's seawater intake.…”

Extreme bottom velocities induced by wind wave and currents in the Gulf of Gdańsk

“…Oey 2008, Oiao et al 1999) also in the Baltic Sea (Dvornikov et al 2017). Model based on POM codes was applied to the study of hydrodynamical conditions in selected regions of the Baltic by Svendsen et al (1996), Jankowski (2000), Paka et al (1998), Anisimov et al (2000) and Zhurbas et al (2003).…”