7.4 Future Scenarios in the Framework of a Changing
Climate
7.4.1 Analyzing the Possible Effects of Climate Change
on Water Circulation, Nutrients, and Primary
Productivity in the Mediterranean and the Alboran Sea
Climate change is expected not only to affect oceanic conditions worldwide (IPCC
2007, 2013; Reid et al. 2009) but also to induce changes in water mass properties and
their associated circulation patterns. As result of changes in water temperature,
stratification, vertical mixing, or in nutrient or light availability, water biochemistry,
and marine ecosystems may be modified (Bopp et al. 2001; Boyd and Doney 2002;
Sarmiento et al. 2004; Steinacher et al. 2010; Taucher and Oschlies 2011).
Due to its modest dimensions, Mediterranean Sea is very sensitive and may
respond rapidly to environmental changes (atmospheric forcing and anthropogenic
influences) (Béthoux and Gentili 1999; Lejeusne et al. 2010; Lionello et al. 2010;
Schroeder et al. 2012, 2017). Expected future changes in the Mediterranean Sea
include an increase in seawater temperature and salinity, reductions in freshwater
inputs (precipitation and river inflow), changes in the ocean-atmosphere heat flux,
and an increase in human pressure (Béthoux and Gentili 1999; Vargas-Yáñez et al.
2008; Sanchez-Gomez et al. 2011; Borghini et al. 2014; García-Martínez et al. 2017;
Macías et al. 2018). All these factors play a crucial role in dense water formation and
hence they determine the circulation in the Mediterranean Sea (Mediterranean
Thermohaline Circulation—MTHC) (Béthoux and Gentili 1999). Changes in circulation can reduce the supply of nutrients, therefore geochemical cycles and PP (also
affected through changes in temperature, pH, light availability, or in atmospheric and
terrestrial inputs of nutrients) of the Mediterranean Sea will be altered (Sarmiento
et al. 2004; Durrieu de Madron et al. 2011; IPCC 2013; Lazzari et al. 2014; Macías
et al. 2014b).
Some studies have carried out a set of numerical experiments to quantify the
sensitivity of the Mediterranean Sea to the twenty-first century climate change
(Adloff et al. 2015). The projections of the possible effects of climate change on
water circulation, nutrients, and primary productivity are studied by developing
“scenarios” (the IPCC SRES, Nakicenovic and Swart 2000). A scenario is a description of a hypothetical future development of the Earth’s societies and economies.
The Intergovernmental Panel on Climate Change “Special Report on Emissions
Scenarios” (SRES) explored pathways of future greenhouse gas emissions, derived
from self-consistent sets of assumptions about energy use, population growth,
economic development, and other factors. Considering the temperature rise by
2100, the “hottest” scenario is A1FI, followed by A2, A1B, B2, A1T; and B1 is
the “coolest.” However, in the A1B and A1T fossil CO 2 emissions are falling by
2100, whereas in A2 and B2 they are still rising, implying that climate impacts
would be greater during the following century. In scenarios A1FI, B1, and B2, CO 2
emissions from land-use change drop below zero.
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T. Ramírez et al.
Climate
7.4.1 Analyzing the Possible Effects of Climate Change
on Water Circulation, Nutrients, and Primary
Productivity in the Mediterranean and the Alboran Sea
Climate change is expected not only to affect oceanic conditions worldwide (IPCC
2007, 2013; Reid et al. 2009) but also to induce changes in water mass properties and
their associated circulation patterns. As result of changes in water temperature,
stratification, vertical mixing, or in nutrient or light availability, water biochemistry,
and marine ecosystems may be modified (Bopp et al. 2001; Boyd and Doney 2002;
Sarmiento et al. 2004; Steinacher et al. 2010; Taucher and Oschlies 2011).
Due to its modest dimensions, Mediterranean Sea is very sensitive and may
respond rapidly to environmental changes (atmospheric forcing and anthropogenic
influences) (Béthoux and Gentili 1999; Lejeusne et al. 2010; Lionello et al. 2010;
Schroeder et al. 2012, 2017). Expected future changes in the Mediterranean Sea
include an increase in seawater temperature and salinity, reductions in freshwater
inputs (precipitation and river inflow), changes in the ocean-atmosphere heat flux,
and an increase in human pressure (Béthoux and Gentili 1999; Vargas-Yáñez et al.
2008; Sanchez-Gomez et al. 2011; Borghini et al. 2014; García-Martínez et al. 2017;
Macías et al. 2018). All these factors play a crucial role in dense water formation and
hence they determine the circulation in the Mediterranean Sea (Mediterranean
Thermohaline Circulation—MTHC) (Béthoux and Gentili 1999). Changes in circulation can reduce the supply of nutrients, therefore geochemical cycles and PP (also
affected through changes in temperature, pH, light availability, or in atmospheric and
terrestrial inputs of nutrients) of the Mediterranean Sea will be altered (Sarmiento
et al. 2004; Durrieu de Madron et al. 2011; IPCC 2013; Lazzari et al. 2014; Macías
et al. 2014b).
Some studies have carried out a set of numerical experiments to quantify the
sensitivity of the Mediterranean Sea to the twenty-first century climate change
(Adloff et al. 2015). The projections of the possible effects of climate change on
water circulation, nutrients, and primary productivity are studied by developing
“scenarios” (the IPCC SRES, Nakicenovic and Swart 2000). A scenario is a description of a hypothetical future development of the Earth’s societies and economies.
The Intergovernmental Panel on Climate Change “Special Report on Emissions
Scenarios” (SRES) explored pathways of future greenhouse gas emissions, derived
from self-consistent sets of assumptions about energy use, population growth,
economic development, and other factors. Considering the temperature rise by
2100, the “hottest” scenario is A1FI, followed by A2, A1B, B2, A1T; and B1 is
the “coolest.” However, in the A1B and A1T fossil CO 2 emissions are falling by
2100, whereas in A2 and B2 they are still rising, implying that climate impacts
would be greater during the following century. In scenarios A1FI, B1, and B2, CO 2
emissions from land-use change drop below zero.
234
T. Ramírez et al.