Climate change, impacts and vulnerability in Europe ... - MemoFin.fr

Climate impacts on environmental systems3 Climate impacts on environmentalsystems3.1 Oceans and marine environment3.1.1 OverviewRelevanceThe oceans play a key role in the regulation ofclimate by transporting heat northward and bydistributing energy from the atmosphere into thedeep parts of the ocean. On the one hand, the GulfStream and its extensions, the north Atlantic currentand drift, influence European weather patterns andstorm tracks. The heat transported northward by theoceanic circulation impacts precipitation and windregimes over Europe. On the other hand, oceansare also affected by the climatic conditions of theatmosphere (see Section 2.2) and the cryosphere(see Section 2.3). The induced changes in physicalocean conditions, in turn, affect the marineecosystems.Selection of indicatorsThis section reviews changes in the followingphysical and biological indicators of oceans andmarine ecosystems in Europe's seas:• Ocean acidification;• Ocean heat content;• Sea surface temperature;• Phenology of marine species;• Distribution of marine species.Key messages: 3.1 Oceans and marine environment• Impacts of climate change are observed in all European seas, although the extent to which impactshave been documented in time and space varies among the seas.• The primary physical impact of climate change in European regional seas is increased sea surfacetemperature. Climate change is expected to impact the physical conditions differently in Europeanregional seas, and consequently biological impacts also vary depending on the region.• North-east Atlantic: Sea surface temperature and ocean heat content are increasing in all regions,although at different rates. Warming is projected to extend throughout the water column during the21st century. Sea surface temperature changes have already resulted in an increased duration of themarine growing season and in northward movement of marine zooplankton. Some fish species areshifting their distributions northward in response to increased temperatures.• Baltic Sea: Future climate change is projected to warm the Baltic Sea, to decrease its salinity, and todecrease sea ice extent by 50–80 % during the 21st century. These changes in physical variables willaffect the ecosystems of the Baltic Sea in many ways. For example, changes in salinity and deep wateroxygen levels are likely to impact cod fisheries by affecting the reproductive success of cod.• Mediterranean Sea: Temperature is projected to increase, and run-off to the Mediterranean Sea todecrease, thereby increasing salinity. Stratification is projected to remain largely constant because ofthe compensating effects of increasing temperature and increasing salinity on the density of sea water.Projected changes in storminess appear to be changing the mixing conditions for nutrients into thesurface layer in the central Mediterranean, leading to nutrient poor conditions. The observed invasionand survival of alien species has been correlated to the warming trend in sea surface temperature.Such invasions not only impact local ecosystems, they can also impact the activities of the internationalfishing fleet.Climate change, impacts and vulnerability in Europe 201289