Geoscience Reference
In-Depth Information
As Moron et al. (1998) noted, the present global warming was considered by
some specialists as connected with sudden changes in the region of the Paci
c
Ocean about 1976 or with a gradual warming of the tropical band of the Paci
c
Ocean as well as with other regional-scale phenomena. The irregular trend men-
tioned above and an attempt to recognize the external forcings on it (anthropogenic
or natural), complicated by the presence of the internally determined variability of
the climate system, have been traditionally based on the interpretation of the trend
as red noise (or, later, on the idea that the trend
'
is variability is determined by that it
is regularly
in noise).
The existence of such regularities has been well established and ascribed mainly
(if not completely) to instability of the interactive
“
immersed
”
“
atmosphere-ocean
”
system in the
tropical Paci
3 years connected
with the ENSO event have been detected. Such regularities on scales of decadal and
inter-decadal variability were more dif
c Ocean. Periodicities of about 4
6 years and 2
-
-
cult to detect in view of insuf
cient length
of the observation series (Krapivin and Nitu 2009).
In this connection, Moron et al. (1998) undertook a detailed analysis of all
available data on the spatial-temporal variability of the SAT
fields of the World
Ocean and for its individual regions with the use of a multi-channel singular
spectral analysis (MSSA). The main goal of analysis was to detect the laws of
variability and inter-basin relationships between SST on time scales from inter-
annual to inter-decadal. The length of observational data series was suf
cient for a
reliable analysis of SST variability on time scales 2
15 years, though the statistical
reliability of results for longer periods is more difficult to guarantee.
In view of a great interest in SST variability in the Atlantic Ocean, the major
attention was given to this region. The strongest climatic signal was an irregular
long-term SST trend. The use of the MSSA method for data processing for the 20th
century revealed the well-known regularities mentioned above: a gradual increase
of SST in both hemispheres in 1910-1940, with the subsequent increase of SST in
the Northern Hemisphere till the mid-1950s; but a lower SST in the Southern
Hemisphere; northern hemisphere ocean cooling in the 1960s until the end of the
1970s; and an initial stability and then increase of SST in both hemispheres in the
1980s with a small weakening of this trend during the last years.
An insuf
-
cient length of the series of instrumental observations makes impos-
sible to interpret the enumerated global laws as a manifestation of more or less
monotonic increase of SST or as part of long-tern centennial oscillations (according
to indirect data, oscillations were observed with periods from 65 to 500 years).
Possible external factors of variability include: the growth of CO
2
concentration,
change of extra-atmospheric insolation, volcanic eruptions. A new and surprising
result was a detection of the fact that a large-scale warming and cooling was
preceded by the same SST variability near the southern edge of Greenland and
(soon after that) in the central part of the Paci
c Ocean in the Northern Hemisphere.
This re
ects an important role of high-latitude processes in the North Atlantic and
possible interaction (via the atmosphere) with the Paci
fl
c Ocean.
12 years) there have not been
observed any regular oscillations, which are coherent on global scales. In the
On time scales of about decadal variability (7
-
Search WWH ::
Custom Search