Enhancement of new production in the northeast subarctic Pacific Ocean during negative North Pacific index events

Citation
Cs. Wong et al., Enhancement of new production in the northeast subarctic Pacific Ocean during negative North Pacific index events, LIMN OCEAN, 43(7), 1998, pp. 1418-1426
Citations number
39
Categorie Soggetti
Aquatic Sciences
Journal title
LIMNOLOGY AND OCEANOGRAPHY
ISSN journal
00243590 → ACNP
Volume
43
Issue
7
Year of publication
1998
Pages
1418 - 1426
Database
ISI
SICI code
0024-3590(199811)43:7<1418:EONPIT>2.0.ZU;2-4
Abstract
We examined interannual variability in the 1965-1990 winter-summer differen ces in surface nitrate (Delta NO3) in the northeast subarctic Pacific Ocean (Station P, 50 degrees N, 145 degrees W). Increases in Delta NO3 of 30-70% above the mean value occurred during four events (1969, 1971-1972, 1979, 1 983). The Delta NO3 time series was highly correlated (r = 0.86) with the s pring-summer nitrate utilization rate from 1970 to 1980. The Delta NO3 time series was negatively correlated with the North Pacific index (NPI) (r = - 0.72) and positively correlated with solar radiation in the spring (r = 0.4 8) and summer (r = 0.46). A simple ecosystem model forced with observed inc ident solar radiation and mixed-layer depth during the spring-summer period predicted increases in export production that were 50% of the observed inc rease for 1970-1972 and 1977-1979. Comparison between the Delta NO3 and sed imenting particulate organic nitrogen (PON) showed that the high Delta NO3 event of 1983 was associated with a dramatic increase in PON fluxes. A simp le ecosystem model underpredicts observed interannual variations in export production, and this result combined with the observed PON fluxes suggests that a combination of increased phytoplankton production and increased f-ra tio produced the observed increase in Delta NO3. The increase inf-ratio imp lies a change in the community structure of the phytoplankton during the el evated Delta NO3 events that appears connected to changes in the NPI.