1) and a strongly variable bathymetry that further limits the exchange between the Baltic Sea sub-basins (Fig. In addition, the Baltic Sea has a low average depth (~ 54 m, Fig. The exchange of water masses with the open ocean is constrained by the narrow and shallow Danish straits.
These differences are partly related to the heterogenous climatic and geomorphological characteristics of the Baltic Sea. Their results demonstrated that seasonal SST changes are very heterogeneous among the sub-basins of the Baltic Sea with for instance twice as much warming in the Baltic proper than in the Bothnian Sea in winter, and the opposite in summer (Kniebusch et al. All studies showed pronounced changes, but to our knowledge only Kniebusch et al ( 2019) analyzed detailed spatial and seasonal heterogeneities. Many studies have analyzed these changes using satellite and in situ SST datasets or with climate models for different periods (e.g. changes in aerosols concentrations), and evaluate accurately the future changes.
#The ephyra we need to go deeper drivers#
Therefore it is critical to characterize and understand the drivers of these historical SST changes, disentangle the impact of climate change from the others changes (e.g. Ultimately, these changes can have an impact to various economic sectors such as fishing or tourism with the summer cyanobacteria blooms (e.g. These physical changes alter also the biogeochemical conditions by, for instance, limiting the supply of nutrient to the euphotic zone. This surface warming has multiple consequences as for instance a thermal stratification enhancement also reduces vertical mixing, or an increased risk of climate extremes such as marine heat waves. The Baltic Sea exhibits outstanding SST changes over the last decades with for instance an increase of 1.35 ☌ in 1982–2006, corresponding to seven times the global rate (Belkin et al. Our results are useful to better understand the historical and future changes of SST in the Baltic Sea, but also in terms of marine ecosystem and public management, and could thus be used for planning sustainable coastal development. Finally, an ensemble of 48 climate change simulations has revealed that for a given RCP scenario the atmospheric forcing is the main source of uncertainty. It was found that the seasonal north/south gradient of SST trends should be reduced in the future due to the vanishing of sea ice, while changes in the frequency of upwelling and heat fluxes explained the lower future east/west gradient of SST trend in fall. To investigate future warming trends climate simulations were performed for the period 1976–2099 using two RCP scenarios. While ice cover explains the seasonal north/south warming contrast, the changes in surface winds and air-sea temperature anomalies (along with changes in upwelling frequencies and heat fluxes) explain the SST trends differences between the sub-basins of the southern part of the Baltic Sea. A classification tree and sensitivity experiments were carried out to analyze the main drivers behind the trends. Our results show that the Baltic Sea can be divided into five different areas of homogeneous SST trends: the Bothnian Bay, the Bothnian Sea, the eastern and western Baltic proper, and the southwestern Baltic Sea. Here, using reconstructed atmospheric forcing fields for the period 1850–2008, oceanic climate simulations were performed and analyzed to identify areas of homogenous SST trends using spatial clustering. Although long-term trends in sea surface temperature (SST) have long been attributed to trends in air temperature, there are however, strong seasonal and sub-basin scale heterogeneities of similar magnitude than the average trend which are not fully explained. The Baltic Sea is one of the fastest-warming semi-enclosed seas in the world over the last decades, yielding critical consequences on physical and biogeochemical conditions and on marine ecosystems.