| dc.description.abstract |
<p>Strengthened stratification of the upper ocean, associated with either anthropogenic
warming trends or natural climate oscillations, is generally expected to inhibit marine
primary productivity at low and mid latitudes, based on the supposition that increased
water column stability will decrease vertical mixing and consequently the upward entrainment
of deep nutrients into the euphotic zone. Herein, we examine the local stratification
control of productivity over the subtropical and equatorial Pacific by directly comparing
a wide range of contemporaneous metrics, drawn from the modern observational record,
for interannual stratification and productivity variability. We find no correlation
between the two in the subtropical North Pacific. In the equatorial Pacific we do
observe a correlation, but find no evidence of a strong causal connection between
the two- instead, our analysis suggest that both biomass and stratification in this
region are impacted by changes in the westward transport, via surface currents, of
relatively cold, nutrient-rich waters that have been upwelled in the eastern Equatorial
Pacific. The importance of horizontal nutrient supply is further evidenced by an analysis
of seasonal variability in the subtropical North Atlantic, where the annual contraction
and expansion of the oligotrophic region appears to be strongly influenced by the
waxing and waning, respectively, of lateral nutrient transfers from neighboring, nutrient
rich waters of the subpolar gyre and the West African upwelling zone.</p>
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