Environmental Engineering Reference
In-Depth Information
more decades, and that this SST pattern was associated with the NPO in
the atmosphere (Kushnir et al. 2002). This SST pattern is called the Pacifi c
Decadal Oscillation (PDO) (Mantua et al. 1997). The Interdecadal Pacifi c
Oscillation (IPO) (Power et al. 1999) is a Pacifi c-wide SST pattern covering
both hemispheres, showing a similar pattern of variability to the PDO in the
North Pacifi c (Folland et al. 2002). The IPO is characterized by year-to-year
and longer-term, predominantly decadal-to-multidecadal, variability of the
Pacifi c Ocean SSTs, with opposite phases between the tropical-subtropical
Pacifi c Ocean and the mid-latitude Pacifi c Ocean in both hemispheres
(Bridgman and Oliver 2006) (Fig. 3b).
Decadal modulation of higher frequency phenomena
There is evidence that shorter-term phenomena, such as El Niño-Southern
Oscillation (ENSO) events, heavy rainfall events and occurrences of
tropical cyclones undergo signifi cant decadal modulation. In particular,
the frequency, intensity, spatial pattern and predictability of interannual
El Niño-Southern Oscillation (ENSO) events have been found to undergo
decadal-multidecadal variability (Kestin et al. 1998, Torrence and Webster
1999, Rajagopalan et al. 2000, England and Huang 2005, Murphy et al.
2010). Predictability of ENSO impacts on Australian climate was found
to be modulated by the IPO such that in the warm IPO phase, there is no
robust relationship between year-to-year Australian climate variations
and ENSO. In the cold IPO phase, year-to-year ENSO variability is closely
associated with year-to-year variability in rainfall, surface temperature,
river fl ow and the domestic wheat crop yield in Australia (Power et al.
1999, Arblaster et al. 2002). Moreover, ENSO impacts on North American
climate were also found to be modulated by the NPO (Bonsal et al. 2001,
Di Lorenzo et al. 2010).
However, it is very important to clearly understand that all these signals
can be expressed simultaneously and not in an isolated way. As an example,
and according to Hunt Jr. and Stabeno (2002) the Bering Sea, as a marginal
ice zone, should be particularly sensitive to climate change, because small
changes in wind velocities can make large differences in the extent, timing
and duration of wintertime sea ice. Although such far-reaching signals as
El Niño/Southern Oscillation (ENSO) on occasion may affect the climate
of the Bering Sea (e.g., Overland et al. 2001), the climate of the southeastern
Bering Sea is most strongly infl uenced by the Pacifi c North American pattern
(PNA) (with which the Pacifi c Decadal Oscillation—PDO—is correlated),
and by the Arctic Oscillation (AO) (Overland et al. 1999). Recent work has
shown that ecosystem responses to decadal-scale changes in these and other
indices of North Pacifi c Ocean and Bering Sea climate have been pervasive
and of great economic importance (Francis et al. 1998, Hare and Mantua
2000, McFarlane et al. 2000, Hollowed et al. 2001).
