for the 500–700 m layer from the works: Fabres et al. (2002), Sanchez-Vidal et al.
(2005), Parrilla et al. (1986) and Kinder (1984).
As already stated, all the Mediterranean waters must finally get out of the
Mediterranean Sea. The contribution of each water mass to the Mediterranean
outflow is variable and our perception about it has changed over the last decades.
Initially, it was assumed that most of the outflow was made of LIW. Kinder and
Parrilla (1987) showed that deep waters would also contribute to the outflow as they
were sucked by the swift Mediterranean current within the Strait (Bernoulli’s
aspiration). More recently, García-Lafuente et al. (2017) have shown that the
proportion of the different water masses contributing to the outflow could be variable
and dependent on the circulation pattern in the upper layer of the Alboran Sea. Welldeveloped anticyclonic gyres would help to evacuate deep water masses, whereas a
coastal mode circulation would inhibit their outflow, favouring the flow of LIW.
4.8 Long-Term Variability
Since mid-1980s, many works have revealed changes in the temperature and salinity
of the water masses of the WMED. Lacombe et al. (1985) compared the results from
different campaigns carried out during the twentieth century and concluded that the
WMDW had increased its potential temperature and salinity from 12.66
C/38.38 to
12.712
C/38.406 from 1909 to 1977. The warming and salinification of the
WMDW were confirmed by Bethoux et al. (1990) who considered that the warming
of the Mediterranean waters was the result of the climate change affecting the world
oceans. Leamann and Schott (1991) and Rohling and Bryden (1992) also observed
the warming and salting of the WMDW and reported the salinity increase of
the LIW. According to these authors, the LIW salinity increase was the result of
the damming of the river Nile and of those rivers draining into the Black Sea. The
salinity increase of the LIW would be the cause for the warming of deep waters. As
the LIW takes part in the WMDW formation, saltier waters would reach the deep
water density with temperature values higher than those from the beginning of the
twentieth century. Krahmann and Schott (1998) detected positive linear trends for
the temperature and salinity of the WMDW, but not for the LIW. These authors
considered that the warming of deep waters was caused by the salinity increase of the
AW, associated with the damming of the river Ebro.
Vargas-Yáñez et al. (2010a, b, 2012b, 2017) showed that the WMDW had
increased its temperature and salinity along the second half of the twentieth century
and that the LIW had increased its salinity. These authors showed that the changes in
the WMDW were robust, and were not sensitive to the data analysis methods. On the
other hand, the LIW results were influenced by the methodology used for the
construction of the annual time series. Nevertheless, more recent works have clearly
shown the temperature and salinity increase of LIW in the Sicily Channel, at least
from 1992 (Schroeder et al. 2017).
102
M. Vargas-Yáñez et al.
(2005), Parrilla et al. (1986) and Kinder (1984).
As already stated, all the Mediterranean waters must finally get out of the
Mediterranean Sea. The contribution of each water mass to the Mediterranean
outflow is variable and our perception about it has changed over the last decades.
Initially, it was assumed that most of the outflow was made of LIW. Kinder and
Parrilla (1987) showed that deep waters would also contribute to the outflow as they
were sucked by the swift Mediterranean current within the Strait (Bernoulli’s
aspiration). More recently, García-Lafuente et al. (2017) have shown that the
proportion of the different water masses contributing to the outflow could be variable
and dependent on the circulation pattern in the upper layer of the Alboran Sea. Welldeveloped anticyclonic gyres would help to evacuate deep water masses, whereas a
coastal mode circulation would inhibit their outflow, favouring the flow of LIW.
4.8 Long-Term Variability
Since mid-1980s, many works have revealed changes in the temperature and salinity
of the water masses of the WMED. Lacombe et al. (1985) compared the results from
different campaigns carried out during the twentieth century and concluded that the
WMDW had increased its potential temperature and salinity from 12.66
C/38.38 to
12.712
C/38.406 from 1909 to 1977. The warming and salinification of the
WMDW were confirmed by Bethoux et al. (1990) who considered that the warming
of the Mediterranean waters was the result of the climate change affecting the world
oceans. Leamann and Schott (1991) and Rohling and Bryden (1992) also observed
the warming and salting of the WMDW and reported the salinity increase of
the LIW. According to these authors, the LIW salinity increase was the result of
the damming of the river Nile and of those rivers draining into the Black Sea. The
salinity increase of the LIW would be the cause for the warming of deep waters. As
the LIW takes part in the WMDW formation, saltier waters would reach the deep
water density with temperature values higher than those from the beginning of the
twentieth century. Krahmann and Schott (1998) detected positive linear trends for
the temperature and salinity of the WMDW, but not for the LIW. These authors
considered that the warming of deep waters was caused by the salinity increase of the
AW, associated with the damming of the river Ebro.
Vargas-Yáñez et al. (2010a, b, 2012b, 2017) showed that the WMDW had
increased its temperature and salinity along the second half of the twentieth century
and that the LIW had increased its salinity. These authors showed that the changes in
the WMDW were robust, and were not sensitive to the data analysis methods. On the
other hand, the LIW results were influenced by the methodology used for the
construction of the annual time series. Nevertheless, more recent works have clearly
shown the temperature and salinity increase of LIW in the Sicily Channel, at least
from 1992 (Schroeder et al. 2017).
102
M. Vargas-Yáñez et al.