Environmental Engineering Reference
In-Depth Information
changing weather patterns (Hinzman et al. 2005). Climate change is already
affecting ecosystems, freshwater supplies, and human health. Although
climate change cannot be avoided entirely, the most severe impacts of
climate change can be avoided by substantially reducing the amount of
heat-trapping gases released into the atmosphere (VijayaVenkataRaman
et al. 2012).
Numerous studies related to different aspects of global climate change
have been published in the last decades (e.g., Crane 1985, Crowley 1992,
Norberg and DeAngelis 1997, Francis et al. 1998, Najjar et al. 2000, Rabalais
et al. 2001, Moss et al. 2003, Straile et al. 2003, Ohring et al. 2005, Occhipinti-
Ambrogi 2007, Adrian et al. 2009, Bardají et al. 2009, Coma et al. 2009,
Collins et al. 2010, Eissa and Zaki 2011, Hollowed et al. 2012, Norris 2012).
Nevertheless, many quite different topics are included within this literature,
and consequently several concepts could be alternatively used in different
ways and scenarios. In order to avoid this kind of problem various central
topics must be clearly defi ned.
One signifi cant aspect of this topic is the understanding of how far
can environmental changes modify the sensitivity of marine systems… In
this sense, Perry et al. (2010a) have defi ned “
sensitivity
” as a measure of
the strength in the relation between the biotic and the climate variables;
for example, increasing sensitivity implies an increasing correlation
between fl uctuations in population abundance (or another characteristic)
and some climate signal, regardless of the mechanism by which climate
variability affects the ecosystem functioning or structure (Lehodey et al.
2006, Drinkwater et al. 2010).
Variability is an inherent characteristic of marine ecosystems (e.g.,
Drinkwater et al. 2010). This variability is due to climate forcing, internal
dynamics such as predator-prey interactions, and anthropogenic forcing
such as fi shing. The latter has occurred for centuries (Jackson et al. 2001,
Poulsen 2010), but is recognized as being globally more intensive since the
onset of industrial fi shing in the 1950s (Pauly et al. 2002, Perry et al. 2010).
Focusing on the issue at hand, it is highly advisable to distinguish between
the two primary components of climate forcing of marine systems: (
i
)
variability
, and (
ii
)
change
(trend). How can each of them be defi ned?
The term “climate variability” is often used to denote deviations of
climate statistics over a given period of time (such as a specifi c month, season
or year) from the long-term climate statistics relating to the corresponding
calendar period (Smit et al. 2000). In this sense, climate variability is
measured by those deviations, which are usually termed
anomalies
.
According to Overland et al. (2010) climate variability occurs on a wide
range of time scales from seasonal periods, to 1-3 year oscillating but erratic
periods (e.g., ENSO), to decadal aperiodic variability like 5-50 years, to
centennial and longer periods. Climate variability includes extreme events,
