Group MeetingGroup Meeting

2010/03/30 R98229014 Kirsten Feng2010/03/30 R98229014 Kirsten Feng

Nutrient and salinity decadal variNutrient and salinity decadal variations in the central and easternations in the central and eastern

North PacificNorth Pacific

E. Di Lorenzo, J. Fiechter, N. Schneider, A. Bracco, E. Di Lorenzo, J. Fiechter, N. Schneider, A. Bracco, A. J. Miller, P. J. S. Franks, S. J. Bograd, A. M. MooA. J. Miller, P. J. S. Franks, S. J. Bograd, A. M. Moore, A. C. Thomas, W. Crawford, A. Pen˜a, and A. J. re, A. C. Thomas, W. Crawford, A. Pen˜a, and A. J.

HermannHermann

Aim Aim

to show that low-frequency variations of suto show that low-frequency variations of surface salinity and upper ocean nutrients alrface salinity and upper ocean nutrients along Line P are explained by the NPGO anong Line P are explained by the NPGO and are positively correlated with the correspd are positively correlated with the corresponding CCS timeseries.onding CCS timeseries.

Family tree Family tree

Alaskan gyreAlaskan gyre

Salinity / NutrientsSalinity / Nutrients

Phase-lockedPhase-locked and and

Strongly correlatedStrongly correlated

California currentCalifornia currentIn PhaseIn Phase

Predict Predict

NPGONPGO (PC-2 of SSHa & SSTa) (PC-2 of SSHa & SSTa)

(Gulf of Alaska,GoA)(Gulf of Alaska,GoA) (California Current System, CCS)(California Current System, CCS)

Also supported by model solutions

Why not PDOWhy not PDO

Analysis of sea surface temperature anomalies (SSAnalysis of sea surface temperature anomalies (SSTa) in the North Pacific have isolated the Pacific DeTa) in the North Pacific have isolated the Pacific Decadal Oscillation (PDO) as the dominant mode of Scadal Oscillation (PDO) as the dominant mode of SSTa variability. The PDO exhibits strong decadal flSTa variability. The PDO exhibits strong decadal fluctuations and regimelike behaviors that have beeuctuations and regimelike behaviors that have been invoked to explain part of the variability of physicn invoked to explain part of the variability of physical and biological properties across the North Pacific.al and biological properties across the North Pacific. However, the PDO However, the PDO fails to capture the prominent lfails to capture the prominent low-frequency fluctuations in salinity and nutrientsow-frequency fluctuations in salinity and nutrients r recorded in the California Current System (CCS) anecorded in the California Current System (CCS) and in the Gulf of Alaska (GoA) Line P timeseries.d in the Gulf of Alaska (GoA) Line P timeseries.

Data Data

NCEPNCEP19501950～～ 20042004surface wind stresses surface wind stresses heat fluxesheat fluxes

Model Model

nutrient-phytoplankton-zooplankton-detritunutrient-phytoplankton-zooplankton-detritus (NPZD) ecosystem model.s (NPZD) ecosystem model.

Regional Ocean Modeling System (ROMRegional Ocean Modeling System (ROMS)S)1/5 of a degree with 30 vertical terrain-followin1/5 of a degree with 30 vertical terrain-followin

g layersg layerseddy-permittingeddy-permittingsuccessfully capture both the mean and long-tsuccessfully capture both the mean and long-t

erm variability of the CCSerm variability of the CCS

Experiment Experiment Figure 1. Temporal and spatial structure of thFigure 1. Temporal and spatial structure of th

e North Pacific Gyre Oscillation (NPGO). (top) e North Pacific Gyre Oscillation (NPGO). (top) Timeseries of NPGO index compared with indTimeseries of NPGO index compared with indices that track the strength of the Kuroshio-Oyices that track the strength of the Kuroshio-Oyashio Extension (KOE, red curve) and North ashio Extension (KOE, red curve) and North Pacific Current (NPC, green curve). The KOE Pacific Current (NPC, green curve). The KOE index is from Taguchi et al. [2007] and lags thindex is from Taguchi et al. [2007] and lags the NPGO by 3 years. The NPC index is from De NPGO by 3 years. The NPC index is from Di Lorenzo et al. [2008] model data and is plotti Lorenzo et al. [2008] model data and is plotted with no time lag. The two indices are comped with no time lag. The two indices are computed by taking the meridional gradient of SSH uted by taking the meridional gradient of SSH over the KOE and NPC regions respectively dover the KOE and NPC regions respectively defined by the black arrows and gray dotted reefined by the black arrows and gray dotted rectangle in Figure 1 (bottom). The indices are ctangle in Figure 1 (bottom). The indices are anomalies from their monthly means. (bottom) anomalies from their monthly means. (bottom) Correlation map between NPGO index and ACorrelation map between NPGO index and AVISO satellite SSHa (1993–2007; http://www.jVISO satellite SSHa (1993–2007; http://www.jason.oceanobs.com). The dark gray rectangle ason.oceanobs.com). The dark gray rectangle shows the spatial domain used to perform the shows the spatial domain used to perform the regional physical-nutrient model hindcast from regional physical-nutrient model hindcast from 1950–2004. Also shown are the locations of t1950–2004. Also shown are the locations of the long-term observations of nutrients and salhe long-term observations of nutrients and salinity from the CalCOFI program in the Californinity from the CalCOFI program in the California Current and Line P in the Gulf of Alaska. Blia Current and Line P in the Gulf of Alaska. Black contours are satellite/drifter-derived mean ack contours are satellite/drifter-derived mean dynamic height [Niiler et al., 2003].dynamic height [Niiler et al., 2003].

Surface SalinitySurface Salinity

Upper Ocean NutrientsUpper Ocean Nutrients

Summary Summary

Even though the NPGO is the second domEven though the NPGO is the second dominant mode of variability of SSHa and SSTinant mode of variability of SSHa and SSTa in the northeast Pacific, it emerges as tha in the northeast Pacific, it emerges as the leading mode of decadal variability for sue leading mode of decadal variability for surface salinity and upper ocean nutrients.rface salinity and upper ocean nutrients.

The patterns of nutrient and salinity variabiThe patterns of nutrient and salinity variability are distinct and similar to their respectility are distinct and similar to their respective mean distributions.ve mean distributions.

Summary Summary

Compared to NPGO, there are positive salCompared to NPGO, there are positive salinity anomalies in the Alaskan gyre and Cainity anomalies in the Alaskan gyre and California Current region, and negative anomlifornia Current region, and negative anomalies in the subtropical gyre.alies in the subtropical gyre.

Thank youThank you～～♫♫

Bon Voyage!Bon Voyage!