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Detection of El Nino and decade time scale variations of sea surface temperature from banded coral records: implications for the carbon dioxide cycle.

Druffel, ERM

UC Irvine Previously Published Works (1985)

Stable oxygen isotope ratios from annually banded corals are correlated with historical records of sea surface temperature in the central and eastern tropical Pacific ocean. El Nino events between 1929 and 1976 are detected using this method, but there are discrepancies between the records of El Ninos from corals and those determined using historical hydrographic and meteorologic data. The average annual description of delta 18O during El Nino events is greater at the Galapagos Island sites (0.45per mille) than at the Fanning and Canton Island sites in the mid-Pacific (0.20-0.30per mille and less than 0.2per mille, respectively). Of prime importance is evidence of decade time scale variability of sea surface temperature (SST) in the tropical Pacific. In particular, annually averaged SST appears to have been 0.5o-1oC higher in the eastern tropical Pacific during the 1930's than during subsequent years. A significant net flux of CO2 from the surface ocean to the atmosphere is envisioned during these periods of higher SST.-Author

Cover page: Detection of El Nino and decade time scale variations of sea surface temperature from banded coral records: implications for the carbon dioxide cycle.

Creative Commons 'BY' version 4.0 license

Article
Peer Reviewed

Radiocarbon in dissolved organic carbon of the South Pacific Ocean

UC Irvine Previously Published Works (2015)

Marine dissolved organic carbon (DOC) originates mainly from primary production using dissolved inorganic carbon (DIC) that has young 14C ages. Paradoxically, the 14C age of deep DOC ranges from 4000 to 6400 14C years, indicating that a portion of DOC survives multiple, deep ocean mixing cycles. Here we show that 14C ages of DOC from the deep South Pacific are equal to those from the deep north central Pacific. This is contrary to DIC 14C ages that increase from south to north in the deep Pacific. We hypothesize that DOC in the South Pacific is influenced by input of ancient DOC from hydrothermal flanks and ridges of the East Pacific Rise. We show that DOC Δ14C values in the deep Pacific are not controlled by aging during northward transport of deep waters, indicating that the deep oceanic carbon cycle needs reassessment.

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Cover page: Radiocarbon in dissolved organic carbon of the South Pacific Ocean

Article
Peer Reviewed

Black Carbon in Deep-Sea Sediments

UC Irvine Previously Published Works (1998)

Black carbon (BC) enters the ocean through aerosol and river deposition. BC makes up 12 to 31 percent of the sedimentary organic carbon (SOC) at two deep ocean sites, and it is 2400 to 13,900 carbon-14 years older than non-BC SOC deposited concurrently. BC is likely older because it is stored in an intermediate reservoir before sedimentary deposition. Possible intermediate pools are oceanic dissolved organic carbon (DOC) and terrestrial soils. If DOC is the intermediate reservoir, then BC is 4 to 22 percent of the DOC pool. If soils are the intermediate reservoir, then the importance of riverine carbon in the ocean carbon cycle has been underestimated.

Cover page: Black Carbon in Deep-Sea Sediments

Article
Peer Reviewed

Radiocarbon in dissolved organic matter in the central North Pacific Ocean

UC Irvine Previously Published Works (1987)

The origin of dissolved organic carbon (DOC) in the ocean has been long debated. Whereas Mantoura and Woodward1have used the conservative nature of DOC in a British estuary to conclude that ≥50% of DOC in the oceans could be river-derived, recent lignin results in the equatorial Pacific2have indicated that ≤10% of the DOC is potentially of terrestrial origin. In addition, the δ13C signature (relative to the PDB standard) of DOC ranges from -20 to -24‰ (refs 3,4), indicating that the primary source of DOC is from marine-derived organic carbon. Here we present the first detailed profile of radiocarbon measured in DOC and dissolved inorganic carbon (DIC) in the oligotrophic gyre of the central North Pacific. δ14C (per mil deviation from the activity of 19th-century wood) of DOC ranged from -150‰ (1,310 yr BP) in surface waters to -540‰ (6,240 yr BP) at 5,710 m, 40 m off the bottom, where these 'apparent ages' or 'residence times' are mean values for the combined constituents of the DOC. The surprising similarity in the shapes of the profiles of δ14C in the DOC and DIC pools suggests that similar processes are controlling the radiocarbon distribution in each of the two reservoirs and that bomb-produced radiocarbon has penetrated the DOC + DIC pools to a depth of ~900 m. The depletion of the δ14CDOCvalues by 300‰ with respect to the δ14CDICvalues suggests that a certain fraction of the DOC is recycled within the ocean on longer time-scales than DIC. © 1987 Nature Publishing Group.

Cover page: Radiocarbon in dissolved organic matter in the central North Pacific Ocean

Article
Peer Reviewed

Changed late Quaternary marine environments on Atlantic continental shelf and upper slope

UC Irvine Previously Published Works (1988)

About 2000 large sediment samples were collected during the early 1960s throughout the continental shelf off the Atlantic coast of the United States to establish and map sediment types including sediments relict from times of glacially low (and subsequently higher) sea levels. In about 510 of these samples we found fossil shells of mollusks remaining from environmental conditions different from those at present. Publications and collections by others contain about 70 additional samples having relict mollusks. Some of these shells indicate lower sea levels, others colder water, and still others warmer water than is now present. Radiocarbon measurements from earlier studies by us and others established the dates of colder water (late Pleistocene), and we made additional measurements to learn the dates of warmer water (about 1000 to 2000 yr B.P.). The results show reasonably enough that continental shelves are the sites of relict faunas as well as of sediments that indicate changed and complex environmental histories. © 1988.

Cover page: Changed late Quaternary marine environments on Atlantic continental shelf and upper slope

Article
Peer Reviewed

Trace metals in contemporary and seventeenth-century Galapagos coral: Records of seasonal and annual variations

UC Irvine Previously Published Works (1990)

We report trace element/calcium ratios for modern ( Cu Ca, Mn Ca, Cd Ca, and Pb Ca) and seventeenth-century ( Cu Ca, Mn Ca, and Pb Ca) specimens of Pavona clavus collected in the Galapagos Islands. These data include the first reliable measurements of Cu Ca ratios in coralline aragonite. We estimate that the ratio of Cu Ca in the lattice to that in seawater (i.e., the effective distribution coefficient) is ~0.3, lower than the value of 1 observed for several other divalent elements; we estimate the effective distribution coefficient for Mn is ~ 1. Distribution coefficients in coral aragonite for 8 divalent metals are near unity despite different ionic radii and chemical speciation in seawater. Investigation of where these substituents are incorporated in the aragonite lattice is clearly warranted. In a modern Hood Island coral, quarter-annually sampled from 1964-73, Cu Ca ratios decrease twofold from the late 1960s to early 1970s. Mn Ca and Cd Ca ratios vary seasonally with upwelling and the generic El Niño. The El Nino Southern Oscillation (ENSO) events of 1965, 1969, and 1972 are marked by suppression of Cd Ca ratios by about 2.5 nmol/mol, while the Mn Ca ratio is highest during the strong 1972 ENSO. Pb Ca ratios were relatively constant throughout this period. From the Cu Ca record of a seventeenth-century Urvina Bay coral annually sampled from 1600-1725 and the estimated Cu distribution coefficient, surface seawater Cu concentrations at Galapagos during the seventeenth century were similar to present day at 0.7-1.4 nmol/kg. Estimated Pb concentrations were lower at 5-20 pmol/kg, and Mn concentrations were slightly higher at 1.6-2.8 nmol/kg. © 1990.

Cover page: Trace metals in contemporary and seventeenth-century Galapagos coral: Records of seasonal and annual variations

Article
Peer Reviewed

Radiocarbon measurements of black carbon in aerosols and ocean sediments

UC Irvine Previously Published Works (2002)

Black carbon (BC) is the combustion-altered, solid residue remaining after biomass burning and fossil fuel combustion. Radiocarbon measurements of BC provide information on the residence time of BC in organic carbon pools like soils and sediments, and also provide information on the source of BC by distinguishing between fossil fuel and biomass combustion byproducts. We have optimized dichromate-sulfuric acid oxidation for the measurement of radiocarbon in BC. We also present comparisons of BC 14C measurements on NIST aerosol SRM 1649a with previously published bulk aromatic 14C measurements and individual polycyclic aromatic hydrocarbon (PAH) 14C measurements on the same NIST standard.Dichromate-sulfuric acid oxidation belongs to the chemical class of BC measurement methods, which rely on the resistance of some forms of BC to strong chemical oxidants. Dilute solutions of dichromate-sulfuric acid degrade BC and marine-derived carbon at characteristic rates from which a simple kinetic formula can be used to calculate concentrations of individual components (Wolbach and Anders, 1989). We show that: (1) dichromate-sulfuric acid oxidation allows precise, reproducible 14C BC measurements; (2) kinetics calculations give more precise BC yield information when performed on a % OC basis (vs. a % mass basis); (3) kinetically calculated BC concentrations are similar regardless of whether the oxidation is performed at 23°C or 50°C; and (4) this method yields 14C BC results consistent with previously published aromatic 14C data for an NIST standard.For the purposes of intercomparison, we report % mass and carbon results for two commercially available BC standards. We also report comparative data from a new thermal method applied to SRM 1649a, showing that thermal oxidation of this material also follows the simple kinetic sum of exponentials model, although with different time constants. © 2002 Elsevier Science Ltd.

Cover page: Radiocarbon measurements of black carbon in aerosols and ocean sediments

Article
Peer Reviewed

Utilization and turnover of labile dissolved organic matter by bacterial heterotrophs in eastern North Pacific surface waters

Faculty Publications (1996)

Seawater incubation experiments were conducted in June and October 1992 to examine bacterial utilization of labile dissolved organic matter (DOM) in open ocean surface waters of the eastern North Pacific. Natural plankton extract-DOM (PE-DOM) and selected model compounds were added to seawater samples to evaluate bacterial utilization and respiration rates relative to bacterial carbon production rates for the various amendments. PE-DOM always stimulated bacterial production and DOM utilization, and the primary nitrogen source supporting this bacterial production was dissolved organic nitrogen (DON). Utilization of DON during exponential growth was balanced by the production of ammonium for samples amended with PE-DOM. Bacterial growth efficiencies for samples amended with PE-DOM ranged between 3.4 and 8.8% and generally were slightly higher in June than in October. Of the model compounds tested, net bacterial biomass production was observed only in samples amended with glucose, glucose plus ammonium (glucose+NH4+), and dissolved free amino acids (DFAA). Bacterial growth efficiencies for these amendments were 0.8, 1.9, and and 9.3.%, respectively. Bacterial production at in situ DOM concentrations was observed in June but not in October. Using the bacterial dissolved organic carbon (DOC) utilization rates observed in this study together with other detailed information pertaining to bulk DOC at our study site, we estimate that the turnover time for labile DOC in these surface waters ranges from approximately 2 to 6 d depending on the lability of the standing stock of DOC. On the basis of (a) the exclusive use of DON as a nitrogen source in PE-DOM amendments, (b) the stimulation of ammonium utilization in the glucose+NH4+ amendment, and (c) the higher growth efficiencies observed for samples amended with either PE-DOM or DFAA, we suggest that bacterioplankton biomass production in eastern North Pacific surface waters is primarily energy limited. As a result of this energy limitation, bacterial production appears to be additionally constrained by the quality of the nutrients available for assimilation. Thus, the quality of the DOM substrate, specifically the DOC:DON ratio, can be a major determinant of bacterial production in pelagic marine systems.

Article
Peer Reviewed

Seasonal cycles of manganese and cadmium in coral from the Galapagos Islands

UC Irvine Previously Published Works (1993)

Manganese-to-calcium ratios in corals from the eastern and western Galapagos demonstrate regional differences in seasonal trace metal cycling. The variability of trace metal-to-calcium ratios within the Galapagos Islands points to their unique geographic setting as a major factor. This region is influenced by several major oceanic currents (e.g., the South Equatorial Current, the Equatorial Undercurrent, and the Panama, or El Niño, Current) and by extremely intense upwelling. Manganese-to-calcium ratios in a banded coral Pavona clavus from Isabela Island, the westernmost island in the Galapagos, have distinct seasonal cycles for the non-El Niño Southern Oscillation (ENSO) years 1946-1950, with lower ratios following intensified seasonal upwelling. Cadmium/calcium ratios show less distinct seasonal cycles. The near-moderate ENSO event in 1951 is marked by the disruption of seasonal cycles in Mn Ca and Cd Ca ratios. In contrast, corals from islands further east in the Galapagos (Hood Island, 1964-1973, Linn et al., 1990; San Cristobal, 1965-1979, Shen and Sanford, 1990), have stronger seasonal Cd Ca signals, with higher ratios following seasonal upwelling, and less distinct seasonal cycles in Mn Ca ratios one-half year out of phase with Cd Ca variations. Average Mn Ca ratios are lower for these corals from locations further east, indicating that Urvina Bay appears to have an additional localized source of Mn (Shen and Sanford, 1990). In general, these regional variations in seasonal trace metal cycling are consistent with coral stable isotope signals and with their geographic locations. These variations are important to consider in using coral records to reconstruct and interpret oceanographic events occurring prior to historical records. © 1993.

Cover page: Seasonal cycles of manganese and cadmium in coral from the Galapagos Islands

Article
Peer Reviewed

Upward fluxes of particulate organic matter in the deep North Pacific

UC Irvine Previously Published Works (1989)

The flux of particulate matter through the oceanic water column is a primary component in elemental cycling and is generally perceived as being in one direction: downward1,2. The organic matter constituting these particles is produced through photosynthesis in surface waters and either sinks directly as phytoplankton and products3,4 or undergoes various trophic transformations through the water column. A large proportion of the particulate organic matter produced in surface waters is regenerated in the euphotic zone5-7. A fraction of this organic matter, however, leaves the surface waters and settles through the water column, generally decreasing in quantity and changing in quality with increasing distance from the surface8-11. Although the net transport of organic matter must be downward to fuel the lower portions of the water column, there is also an upward component to transport. Positively buoyant particles, including lipid-rich eggs, larvae and, possibly, carcasses of deep-sea animals are examples of particles which undergo upward transport12,13. A previous attempt to quantify the upward mass flux indicated rates of 1-4% of the downward mass flux14. Here we report the first evidence that there is a significant upward flux of particulate organic matter, up to 66.7% of the concurrently measured downward flux, at two stations in the deep North Pacific. Given this magnitude, the previously ignored upward flux of such organic matter must be considered in models of carbon and nitrogen cycling in the open ocean. © 1989 Nature Publishing Group.

Cover page: Upward fluxes of particulate organic matter in the deep North Pacific