Should Swedish sea level planners worry more about mean sea level rise or sea level extremes?

Current coastal spatial planning in Sweden uses simple methods to account for how flood risks increase owing to sea level rise. Those methods, however, fail to account for several important aspects of sea level rise, such as: projection uncertainty, emission scenario uncertainty and time dependence. Here, enhanced methods that account for these uncertainties are applied at several locations along the coast. The relative importance of mean sea level rise and extreme events for flood risk is explored for different timeframes. A general conclusion for all locations is that, extreme events dominate the flood risk for planning periods lasting a few decades. For longer planning periods, lasting toward the end of the century, the flood risk is instead dominated by the risk of high sea level rise. It is argued that these findings are important for assessments of future flood risk, and that they should be reflected in coastal spatial planning.

Sea-level rise projections for Sweden based on the new IPCC special report: The ocean and cryosphere in a changing climate.

New sea-level rise projections for Sweden are presented. Compared to earlier projections, we have here, more carefully, taken regional variations in sea-level rise into consideration. The better treatment of regional variations leads to lower sea-level rise projections for Sweden. However, recent research has also shown that Antarctic ice loss, in high emission scenarios, could be greater than what was believed earlier. Taking also this into account, we find a near cancellation between the increased Antarctic contribution and the decrease owing to the better treatment of spatial inhomogeneities. Sweden's sensitivity to melt from Antarctica and Greenland is also estimated using a new set of sea-level fingerprint kernels, and the sensitivity to melt from Greenland is found to be weak. To illustrate the influence mean sea-level rise has on extreme sea levels, it is also shown how the return period of sea-level extremes changes as a function of time owing to mean sea-level rise in the different projections.

Improving oxygen conditions in the deeper parts of bornholm sea by pumped injection of winter water.

Vertical diffusivity and oxygen consumption in the basin water, the water below the sill level at about 59 m depth, have been estimated by applying budget methods to monitoring data from hydrographical stations BY4 and BY5 for periods without water renewal. From the vertical diffusivity, the mean rate of work against the buoyancy forces below 65 m depth is estimated to about 0.10 mW m(-2). This is slightly higher than published values for East Gotland Sea. The horizontally averaged vertical diffusivity κ can be approximated by the expression κ = a 0 N (-1) where N is the buoyancy frequency and a 0 ≈ 1.25 × 10(-7) m(2) s(-2), which is similar to values for a 0 used for depths below the halocline in Baltic proper circulation models for long-term simulations. The contemporary mean rate of oxygen consumption in the basin water is about 75 g O2 m(-2) year(-1), which corresponds to an oxidation of 28 g C m(-2) year(-1). The oxygen consumption in the Bornholm Basin doubled from the 1970s to the 2000s, which qualitatively explains the observed increasing frequency and vertical extent of anoxia and hypoxia in the basin water in records from the end of the 1950s to present time. A horizontally averaged vertical advection-diffusion model of the basin water is used to calculate the effects on stratification and oxygen concentration by a forced pump-driven vertical convection. It is shown that the residence time of the basin water may be reduced by pumping down and mixing the so-called winter water into the deepwater. With the present rate of oxygen consumption, a pumped flux of about 25 km(3) year(-1) would be sufficient to keep the oxygen concentration in the deepwater above 2 mL O2 L(-1).