Climate change impacts and vulnerability in Europe 2016

Climate change impacts on environmental systems
4.1 Oceans and marine environment
Key messages
• The primary impacts of climate change observed in Europe's seas are acidification, increased ocean heat content and
increased sea surface temperature. The extent to which physical impacts have been documented varies among the seas.
• Climate change affects physical conditions differently in Europe's seas, and consequently its biological impacts also vary
depending on the region. Ocean temperature is one of the strongest regulators of marine life. Changes in temperature
cause significant shifts in the distribution of marine species, both horizontally, towards the poles, and vertically, with
changes in depth distribution.
• The impacts of climate change in combination with synergistic impacts of other anthropogenic stressors will potentially
cause widespread changes to marine ecosystems and ultimately the services and benefitss humans receive from the seas.
• North-east Atlantic Ocean: sea surface temperature and ocean heat content are increasing in all regions, although
at different rates. Sea surface temperature changes have already resulted in an increased duration of the marine
growing season and in the northwards movement of marine zooplankton. Marine species are shifting their distributions
northwards in response to increased temperatures. Of the commonly observed demersal fish species, 72 % have
experienced changes in abundance and/or distribution in response to warming waters. This change has already had
important impacts on fisheries in this region.
• Baltic Sea: future climate change is projected to warm the Baltic Sea, to decrease its salinity, to decrease sea ice extent by
50–80 % during the 21st century, and to further expand oxygen depleted 'dead zones'. These changes in physical variables
will have predominantly negative impacts on the Baltic Sea ecosystems.
• Mediterranean Sea: temperature is projected to increase, and run-off to the Mediterranean Sea is projected to decrease,
thereby increasing salinity. Stratification is projected to remain largely constant because of the compensating effects of
increasing temperature and increasing salinity on the density of sea water. The observed invasion and survival of alien
species has been correlated with the warming trend in sea surface temperature.
4.1.1 Overview
Relevance
The oceans cover about 72 % of the Earth's surface.
Oceans interact closely with the atmosphere. On the
one hand, oceans influence weather patterns on local
to global scales. On the other hand, changes in the
atmosphere can alter the properties of the oceans.
Changes in ocean properties driven by an increase
in atmospheric greenhouse gas concentrations,
such as ocean acidification and warming, can have
a substantial impact on marine ecosystems, their
productivity and marine biodiversity, and thus
ecosystem-service provision (Walther et al., 2002;
Lotze et al., 2006; Ruckelshaus et al., 2013).
The atmospheric concentrations of greenhouse
gases, such as CO 2 , have increased substantially since
pre‐industrial times, thus trapping increasingly more
solar energy within the atmosphere (see Section 3.1).
Most of this heat is stored by the ocean, where it
affects sea surface temperature, ocean heat content,
sea levels, salinity, ocean circulation and sea ice
cover. The rest melts ice and warms the atmosphere
and land. The ocean also absorbs significant amounts
of CO 2 from the atmosphere, thereby mitigating the
magnitude of climate change. However, the increased
levels of dissolved carbon are changing the chemistry
of seawater and making it more acidic. Sea level rise
is addressed in Section 4.2.
Changes to the physical and chemical properties of
the ocean can have substantial impacts on marine
biodiversity and thus alter marine ecosystem
productivity, functioning and ecosystem-service
provision. As such, climate change affects the
health and resilience of marine ecosystems and the
provision of services to society, such as through
fisheries. These effects of climate change are now
being seen in all of Europe's seas, although the
extent to which impacts have been documented
106 Climate change, impacts and vulnerability in Europe 2016 | An indicator-based report