Climate simulations for the North Atlantic and Europe for recent and future conditions simulated with the regionally coupled ROM model are analyzed and compared to the results from the MPI‐ESM. The ROM simulations also include a biogeochemistry and ocean tides. For recent climate conditions, ROM generally improves the simulations compared to the driving model MPI‐ESM. Reduced oceanic biases in the Northern Atlantic are found, as well as a better simulation of the atmospheric circulation, notably storm tracks and blocking. Regarding future climate projections for the 21st century following the RCP 4.5 and 8.5 scenarios, MPI‐ESM and ROM largely agree qualitatively on the climate change signal over Europe. However, many important differences are identified. For example, ROM shows an SST cooling in the Subpolar Gyre, which is not present in MPI‐ESM. Under the RCP8.5 scenario, ROM Arctic sea ice cover is thinner and reaches the seasonally ice‐free state by 2055, well before MPI‐ESM. This shows the decisive importance of higher ocean resolution and regional coupling for determining the regional responses to global warming trends. Regarding biogeochemistry, both ROM and MPI‐ESM simulate a widespread decline in winter nutrient concentration in the North Atlantic of up to ~35%. On the other hand, the phytoplankton spring bloom in the Arctic and in the North‐Western Atlantic starts earlier, and the yearly primary production is enhanced in the Arctic in the late 21st century. These results clearly demonstrate the added value of ROM to determine more detailed and more reliable climate projections at the regional scale.
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.
Abstract. We investigate the effect of variable marine biogeochemical light
absorption on Indian Ocean sea surface temperature (SST) and how this
affects the South Asian climate. In twin experiments with a regional Earth
system model, we found that the average SST is lower over most of the domain
when variable marine biogeochemical light absorption is taken into account,
compared to the reference experiment with a constant light attenuation
coefficient equal to 0.06 m−1. The most significant deviations (more than
1 ∘C) in SST are observed in the monsoon season. A considerable
cooling of subsurface layers occurs, and the thermocline shifts upward in
the experiment with the activated biogeochemical impact. Also, the
phytoplankton primary production becomes higher, especially during periods
of winter and summer phytoplankton blooms. The effect of altered SST
variability on climate was investigated by coupling the ocean models to a
regional atmosphere model. We find the largest effects on the amount of
precipitation, particularly during the monsoon season. In the Arabian Sea,
the reduction of the transport of humidity across the Equator leads to a
reduction of the large-scale precipitation in the eastern part of the basin,
reinforcing the reduction of the convective precipitation. In the Bay of
Bengal, it increases the large-scale precipitation, countering convective
precipitation decline. Thus, the key impacts of including the full
biogeochemical coupling with corresponding light attenuation, which in turn
depends on variable chlorophyll a concentration, include the enhanced
phytoplankton primary production, a shallower thermocline, and decreased SST and
water temperature in subsurface layers, with cascading effects upon the
model ocean physics which further translates into altered atmosphere
dynamics.
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