Page 44 - HydrographyReadMe

Climatology Comparison with ENSO,

PDO, and NPGO

Although there is a large annual cycle in Strait of Georgia water properties, there are also
year-to-year changes that are correlated with large-scale changes over the Pacific. Three of
these large-scale patterns are known:

El Niño/Southern Oscillation (ENSO).

ENSO is the most important indicator for global climate disruptions that can last for several
seasons, and is related to processes occurring in the equatorial Pacific. Over BC land areas,
positive ENSO values usually indicate warmer temperatures, with weaker winter snowfall
(more of which falls as rain) due to changes in wind patterns, but in coastal areas may be
associated with weaker upwelling. Negative ENSO conditions usualy imply the opposite. Here
we show a Multivariate ENSO Index.

Pacific Decadal Oscillation (PDO)

The PDO is the most important mode of variability in the North Pacific. It is a multi-decadal
cycle in temperature and sea-surface height conditions. Positive index conditions are
generally associated with warmer waters in the eastern pacific (and colder waters in the
western Pacific), with the opposite in negative index conditions.

North Pacific Gyre Oscillation (NPGO)

The NPGO is the second most dominant mode of sea-surface height variability in the north-
east Pacific (related to changes in the gyre circulation pattern). It appears to be correlated
with salinity and nutrient variations (and hence in Chlorophyll concentrations) in Alaska and
the California coast.

Here we compare our "Red/Blue" climatology indicators (with red meaning values above the
seasonal climatology, and blue values below the seasonal climatology) with indexes for these
3 climate variations.