Spatial and temporal variability of POC in the northeast Subarctic Pacific

Abstract Particulate organic carbon (POC) concentrations from 0 to 1000 m were quantified in size-fractionated particulate matter samples obtained by the multiple unit large volume in situ filtration system (MULVFS) in 1996 and 1997 along the 1600 km long “line P” transect from continental slope waters near southern Vancouver Island to Ocean Station PAPA (OSP, 50°N, 145°W). Regression of in situ POC vs. beam attenuation coefficient, c , from a simultaneously deployed 1-m pathlength SeaTech transmissometer gave slope, intercept and r 2 values of 6.15±0.19×10 −5  m −1 (nmol C l −1 ) −1 , 0.363±0.003 m −1 , and 0.951 ( n =145), respectively. This result agreed within several percent of calibrations obtained from two 2600-km-long transects of the equatorial Pacific in 1992 ( Bishop, 1999 ). Data from other, more frequently deployed transmissometers were standardized against the 1-m instrument, and the combined optical data set was used to document POC variability at finer spatial and temporal scales than could be sampled directly using either conventional water bottle casts or MULVFS. Published bottle POC vs. c relationships show much more variability and remain problematic. Along the line P transect in the salinity-stratified upper 100 m, POC isolines shoaled from winter to summer in concert with seasonal stratification. At the same time, POC was progressively enriched in subeuphotic zone waters to depths greater than 500 m. Near-surface POC fields sampled in the winter time showed strong temporal POC variability over time scales of days as well as between years. POC concentrations at OSP in February 1996 were higher than those found at any other time of year. Less variability was found along line P in other seasons. In May 1996, kilometer-scale spatial variability of POC at OSP was small; dawn vs. dusk variations of c were used to calculate 0–100 m POC turnover times shorter than 6 d. Calculations also suggest that 25–50% of primary productivity was expressed as dissolved organic carbon at OSP in May 1996.

[1]  O. Brown,et al.  Observations of offshore shelf-water transport induced by a warm-core ring , 1992 .

[2]  J. Cochran,et al.  Export flux of carbon at the equator during the EqPac time-series cruises estimated from 234Th measurements , 1996 .

[3]  M. Landry,et al.  Beam attenuation and micro-organisms: spatial and temporal variations in small particles along 140°W during the 1992 JGOFS EqPac transects , 1996 .

[4]  James K. B. Bishop,et al.  The correction and suspended particulate matter calibration of Sea Tech transmissometer data , 1986 .

[5]  Suzanne Roy,et al.  The downward flux of biogenic material in the NE subarctic Pacific: importance of algal sinking and mesozooplankton herbivory , 1999 .

[6]  S. Giovannoni,et al.  Transformations of biogenic particulates from the pelagic to the deep ocean realm , 1999 .

[7]  L. Balistrieri,et al.  234Th and particle cycling in the central equatorial Pacific , 1997 .

[8]  K. Denman,et al.  A coupled 1-D biological/physical model of the northeast subarctic Pacific Ocean with iron limitation , 1999 .

[9]  D. Mackas,et al.  Mesozooplankton community characteristics in the NE subarctic Pacific , 1999 .

[10]  Charles B. Miller.  Pelagic production production in the Subacrtic Pacific , 1993 .

[11]  R. Weller,et al.  Bio‐optical variability associated with phytoplankton dynamics in the North Atlantic Ocean during spring and summer of 1991 , 1995 .

[12]  James K. B. Bishop,et al.  Transmissometer measurement of POC , 1999 .

[13]  D. Ketten,et al.  The chemistry, biology, and vertical flux of particulate matter from the upper 400 m of the equatorial Atlantic Ocean , 1977 .

[14]  Wilford D. Gardner,et al.  The oceanic mixed-layer pump , 1995 .

[15]  K. Denman,et al.  Evidence of change in the winter mixed layer in the Northeast Pacific Ocean , 1997 .

[16]  K. S. Baker,et al.  Springtime distributions and variability of biogenic particulate matter in Gulf Stream warm-core ring 82B and surrounding N.W. Atlantic waters , 1992 .

[17]  M. J. Richardson,et al.  Biophysical forcing of particle production and distribution during a spring bloom in the North Atlantic , 1993 .

[18]  R. Sherrell,et al.  A multiple-unit large-volume in situ filtration system for sampling oceanic particulate matter in mesoscale environments , 1985 .

[19]  W. Broenkow,et al.  VERTEX: biological implications of total attenuation and chlorophyll and phycoerythrin fluorescence distributions along a 2000 m deep section in the Gulf of Alaska , 1992 .

[20]  James K. B. Bishop,et al.  Spatial distributions and variability of suspended particulate matter in warm-core ring 82B , 1986 .

[21]  R. Weller,et al.  Bio-optical and physical variability in the subarctic North Atlantic Ocean during the spring of 1989 , 1994 .

[22]  Wilford D. Gardner,et al.  The diel cycle in the integrated particle load in the equatorial Pacific: A comparison with primary production , 1995 .

[23]  J R Zaneveld,et al.  Effect of particle size distribution and chlorophyll content on beam attenuation spectra. , 1982, Applied optics.

[24]  J. Ronald,et al.  A Transmissometer For Profiling And Moored Observations In Water , 1978, Optics & Photonics.

[25]  W. Broenkow,et al.  Vertex: phytoplankton/iron studies in the Gulf of Alaska , 1989 .

[26]  S. Tabata.  Annual and interannual variability of baroclinic transports across Line P in the northeast Pacific Ocean , 1991 .

[27]  A. Vézina,et al.  Inverse modeling of carbon and nitrogen flows in the pelagic food web of the northeast subarctic Pacific , 1999 .

[28]  W. K. Johnson,et al.  Seasonal and interannual variability in particle fluxes of carbon, nitrogen and silicon from time series of sediment traps at Ocean Station P, 1982–1993: relationship to changes in subarctic primary productivity , 1999 .

[29]  S. Bograd,et al.  Near-surface circulation of the northeast Pacific Ocean derived from WOCE-SVP satellite-tracked drifters , 1999 .

[30]  R. Bidigare,et al.  Seasonal variability of bio-optical and physical properties in the Sargasso sea , 1993 .

[31]  J. Zaneveld,et al.  Intermediate Nepheloid Layers Observed off Oregon and Washington , 1980 .

[32]  Curtiss O. Davis,et al.  Photosynthetic characteristics and estimated growth rates indicate grazing is the proximate control of primary production in the equatorial Pacific , 1992 .

[33]  H. Freeland,et al.  Variability in upper-ocean water properties in the NE Pacific Ocean , 1999 .

[34]  M. Charette,et al.  as a tracer of particulate organic carbon export in the subarctic northeast Pacific Ocean , 1999 .

[35]  H. V. Hulst.  Light Scattering by Small Particles , 1957 .

[36]  Ann E. Gargett,et al.  Multiple thermoclines are barriers to vertical exchange in the subarctic Pacific during SUPER, May 1984 , 1988 .

[37]  P. Boyd,et al.  Interannual variability in nitrate supply to surface waters of the Northeast Pacific Ocean , 1998 .

[38]  K. Denman,et al.  The seasonal cycle in sinking particle fluxes off Vancouver Island, British Columbia , 1999 .

[39]  P. Boyd,et al.  Phytoplankton dynamics in the NE subarctic Pacific , 1999 .

[40]  Dale A. Kiefer,et al.  Meridional variations in the concentration of chlorophyll and microparticles in the North Pacific Ocean , 1988 .

[41]  Tommy D. Dickey,et al.  Optical determination of particulate abundance and production variations in the oligotrophic ocean , 1989 .