Santa Barbara Basin Research Articles

Influence of Boundary Scavenging and Sediment Focusing on234Th,228Th and210Pb Fluxes in the Santa Barbara Basin

Sediment trap samples were collected from the Santa Barbara Basin to examine the flux of234Th,228Th and210Pb. Mean ratios of measured to predicted fluxes are 2, 10 and 21 for234Th,228Th and210Pb, respectively. Boundary scavenging may supply a portion of all three radionuclides. However, sediment focusing supplies additional228Th and210Pb but little234Th. Sediment temporarily deposited on the shelf around the basin contains little excess234Th due to its short half-life.228Th and210Pb fluxes to the sediments in the Santa Barbara Basin are several times greater than predicted from their supply in the overlying water column. These enhanced fluxes require lateral transport of228Th and210Pb to the basin through boundary scavenging and sediment focusing.234Th flux is poorly correlated with228Th and210Pb fluxes because individual radionuclide sources to the basin differ (i.e. water column production, boundary scavenging and/or sediment focusing). Correlations between228Th and210Pb fluxes are high due to the strong influence of sediment focusing on both radionuclides. There is a strong correlation between both the228Th and210Pb flux and total mass flux and lithogenic flux, but a weak correlation with the other major sediment components (e.g. organic carbon, carbonate and biogenic opal). In the Santa Barbara Basin, a large fraction of the total mass flux is lithogenic material (50–80%), hence the strong correlation between228Th and210Pb fluxes and both total mass and lithogenic fluxes.234Th flux is poorly correlated with total mass and major sediment component fluxes.

An alkenone (U37K′) quasi-annual sea surface temperature record (A.D. 1440 to 1940) using varved sediments from the Santa Barbara Basin

Analyses for C37 alkenones (U37K′) and total organic carbon (TOC) in a varved core from the depocenter of the Santa Barbara Basin (34°13.5′N, 120°01′W, 590 m water depth) have been made on an approximately 1–2 year basis from A.D. 1440 to 1940. The U37K′-based sea surface temperature (SST) record oscillates around 15.5°C with an amplitude of less than 3°C at approximately interannual, decadal, and centennial frequencies. Historical El Niño/Southern Oscillation (ENSO) events are matched only partially by warmer U37K′ SSTs. Three records: our SST, a published Pacific coral δ18O, and a published tree-ring temperature anomaly from the California valleys, show no evidence of colder temperatures during the Little Ice Age (ca. 1500 to 1840 A.D.). Significantly, there is a strong centennial-scale cyclicity in the U37K′ SST record which approaches 1°C in amplitude. TOC burial and alkenone fluxes are largely controlled by sedimentation rate as expressed in varve thickness.

Rapid oscillations in western North America vegetation and climate during oxygen isotope stage 5 inferred from pollen data from Santa Barbara Basin (Hole 893A)

Chronologically-controlled, high-resolution (∼200 yr average sampling interval) pollen data from a core in the Santa Barbara Basin (SBB) provide evidence of millennial-scale climate variability on the southern California coast from ∼70 to 140 ka B.P. The first climate event, inferred from a brief reversal in the glacial/interglacial shift from montane conifer to lowland oak assemblages, occurred during the oxygen isotope stage (OIS) 6/5 transition. In OIS 5e, oak-dominated assemblages imply conditions similar to or slightly warmer than present. Cooler conditions that gradually replaced the relatively stable warm Mediterranean climate that continued across the OIS 5e/5d transition ended abruptly just before the end of OIS 5d. Warming, inferred from oak expansion, continued in OIS 5c. This lengthy cyclic sequence of high amplitude warming events, which peaked below interglacial values, extended into the first part of OIS 5b. Similar oscillations occurred in OIS 5a. These pollen data, that are directly correlated with isotopic data from the same sediment samples from Hole 893A, support previous observations that the last interglacial ( sensu stricto) on the west coast of North America was correlative with oxygen isotope substage 5e. In addition, pollen data show that significant warming events reflected in terrestrial vegetation also occurred in different background states of the climate system — during processes of ice growth as well as ice decay.

Nitrogen isotope variations in Santa Barbara Basin sediments: Implications for denitrification in the eastern tropical North Pacific during the last 50,000 years

Nitrogen isotope variations preserved in Santa Barbara Basin sediments are used to evaluate changes in denitrification in the eastern tropical North Pacific (ETNP) during the last 50,000 years. A significant component of the subsurface waters (∼100–400 m) that presently fill the Santa Barbara Basin is derived from the low‐oxygen, denitrifying zone in the ETNP, and the nitrate in these waters has a δ15N value of 8–9‰. During the last glacial, the δ15N values of Santa Barbara Basin sediments were typically 6–7‰, indicating decreased denitrification in the ETNP and a better oxygenated intermediate water mass in the Santa Barbara Basin at this time. This reduced denitrification during the last glacial would have increased the pool of fixed nitrogen and may have contributed to the higher productivity previously reported for various regions of the global ocean during this period. At the onset of deglaciation, sediment δ15N values increase by more than 2‰, indicating increased denitrification in the ETNP. During Younger Dryas time, δ15N values decreased by 3‰ and record a brief return to better ventilated conditions in the subsurface waters of the ETNP. This is followed by an increase in δ15N to over 9‰ at ∼10,000 years ago, indicating intense denitrification at the beginning of the Holocene.

Structural control of fluid flow: offshore fluid seepage in the Santa Barbara Basin, California

Evidence of active and dormant fluid seepage in the Santa Barbara Basin is observed as active venting of gas and oil, bacterial mats, precipitates of authigenic carbonate, and mud and tar volcanoes. Fluid seepage occurs preferentially in the proximity to faults and faulted anticlines, and to slump scarps. Seepage next to faults and anticlines indicates that hydrocarbon migration and pore fluid expulsion is controlled structurally, with faults acting as preferred conduits for fluid flow across units of low matrix permeability.

Metabolism of benthic octopods (Cephalopoda) as a function of habitat depth and oxygen concentration

The oxygen consumption rates and activities of key metabolic enzymes were measured and analyzed as a function of habitat depth for several species of benthic octopod (Cephalopoda: Octopoda) including a recently described hydrothermal vent endemic species. Oxygen consumption rates and citrate synthase activity, an indicator of aerobic metabolic potential, did not vary significantly with increasing habitat depth. Anaerobic metabolic potential, as evidenced by octopine dehydrogenase activity, declined significantly with increasing habitat depth. It is suggested that burst swimming abilities, and hence glycolytic potential, are not strongly selected for in the deep-sea, where visual predator-prey interactions are reduced because of light-limitation. Oxygen consumption rates for Octopus californicus and O. bimaculoides were analyzed as a function of oxygen partial pressure as well. O. californicus, which lives in the hypoxic Santa Barbara basin at 500 m depth, was able to regulate its oxygen consumption to the limit of detectable oxygen partial pressures. O. bimaculoides, an intertidal species, had a minimum critical oxygen partial pressure of 16 mmHg. It is also shown that oxygen consumption rates and oxygen consumption regulation are strongly affected by individual experiment duration (either handling stress or food deprivation). O. californicus appears to be much more strongly affected by experiment duration than is O. bimaculoides.

Carbon isotopic evidence for methane hydrate instability during quaternary interstadials

Large (about 5 per mil) millennial-scale benthic foraminiferal carbon isotopic oscillations in the Santa Barbara Basin during the last 60,000 years reflect widespread shoaling of sedimentary methane gradients and increased outgassing from gas hydrate dissociation during interstadials. Furthermore, several large, brief, negative excursions (up to -6 per mil) coinciding with smaller shifts (up to -3 per mil) in depth-stratified planktonic foraminiferal species indicate massive releases of methane from basin sediments. Gas hydrate stability was modulated by intermediate-water temperature changes induced by switches in thermohaline circulation. These oscillations were likely widespread along the California margin and elsewhere, affecting gas hydrate instability and contributing to millennial-scale atmospheric methane oscillations.

Planktonic foraminiferal fluxes in the Santa Barbara Basin: response to seasonal and interannual hydrographic changes

Results of a three-year time-series sediment trap experiment in the Santa Barbara Basin indicate linkages between water-column dynamics and variations in plankton fluxes on both seasonal and interannual time scales. The two-week collection interval utilized for this study allows evaluation of high-frequency changes in the production and flux of planktonic foraminifera, which are compared to those of siliceous microorganisms (diatoms, radiolaria and silicoflagellates). Annual hydrographic conditions in Santa Barbara Basin are influenced by seasonal changes in insolation, the wind field and source waters. This study includes periods of weak to moderate El Niño conditions followed by a transitional period to a non-El Niño state. Planktonic foraminiferal fluxes and species turnover are related to seasonal and interannual changes in source waters and water column conditions. Globigerina bulloides, G. quinqueloba and Neogloboquadrina pachyderma (dextral) dominate the planktonic foraminiferal population in this location and are present throughout the year. Globigerina bulloides and G. quinqueloba have similar flux patterns, and highest fluxes occur in association with diatom blooms. The flux patterns of G. bulloides and G. quinqueloba in general are inversely related to that of N. pachyderma (dextral). Globigerina quinqueloba seems to respond earlier to the onset of upwelling than G. bulloides. Three temperature-limited species, Neogloboquadrina dutertrei, Orbulina universa and Globigerinoides ruber, are present in lower numbers and show more restricted seasonal ranges. In the thermal regime of the Santa Barbara Basin, N. dutertrei, like O. universa, disappears during upwelling. Neogloboquadrina dutertrei occurs in highest abundance when the water column is thermally stratified and there is a well developed deep chlorophyll maximum. Increased fluxes of Globigerinoi ruber the most thermally restricted of the dominant species in the basin, are associated with the presence of warm oceanic diatoms and warm-water radiolarians. Total planktonic foraminiferal fluxes were lower in 1995 than during the previous two years, which were characterized by El Niño conditions.

Dansgaard‐Oeschger Cycles and the California Current System: Planktonic foraminiferal response to rapid climate change in Santa Barbara Basin, Ocean Drilling Program Hole 893A

High‐resolution planktonic foraminiferal census data from Santa Barbara Basin (Ocean Drilling Program hole 893A) demonstrate major assemblage switches between 25 and 60 ka that were associated with Dansgaard‐Oeschger cycles. Stadials dominated by Neogloboquadrina pachyderma (sinistral), and Globigerinoides glutinata suggest a strong subpolar California Current influence, while interstadials marked by abundant N. pachyderma (dextral) and G. bulloides indicate a relative increase in subtropical countercurrent influence. Modern analog technique and transfer function (F‐20RSC) temperature reconstructions support δ18O evidence of large rapid (70 years or less) sea surface temperature shifts (3° to 5°C) between stadials and interstadials. Changes in the vertical temperature gradient and water column structure (thermocline depth) are recorded by planktonic faunal oscillations suggest bimodal stability in the organization of North Pacific surface ocean circulation. Santa Barbara Basin surface water demonstrates the rapid response of the California Current System to reorganization of North Pacific atmospheric circulation during rapid climate change.Supporting assemblage data are, available on diskette or via Anonymous FTP from Kosmos.agu.org, Directory APEND (username = anonymous, Password = guest). Diskette may be ordered from American Geophysical Union, 2000 Florida Avenue, N.W., Washington, DC 20009 or by phone at 800‐966‐2481; $5.00. Payment must accompany order.

The Santa Barbara Basin is a symbiosis oasis.

It is generally agreed that the origin and initial diversification of Eucarya occurred in the late Archaean or Proterozoic Eons when atmospheric oxygen levels were low and the risk of DNA damage due to ultraviolet radiation was high. Because deep water provides refuge against ultraviolet radiation and early eukaryotes may have been aerotolerant anaerobes, deep-water dysoxic environments are likely settings for primeval eukaryotic diversification. Fossil evidence shows that deep-sea microbial mats, possibly of sulphur bacteria similar to Beggiatoa, existed during that time. Here we report on the eukaryotic community of a modern analogue, the Santa Barbara Basin (California, USA). The Beggiatoa mats of these severely dysoxic and sulphidic sediments support a surprisingly abundant protistan and metazoan meiofaunal community, most members of which harbour prokaryotic symbionts. Many of these taxa are new to science, and both microaerophilic and anaerobic taxa appear to be represented. Compared with nearby aerated sites, the Santa Barbara Basin is a 'symbiosis oasis' offering a new source of organisms for testing symbiosis hypotheses of eukaryogenesis.

A 160-k.y.-old record of El Niño–Southern Oscillation in marine production and coastal runoff from Santa Barbara Basin, California, USA

A 160-k.y.-old laminated sediment record from the Santa Barbara Basin, California, analyzed using scanning electron microscope techniques, provides a history of interannual variability of marine production and coastal runoff. We used backscatter electron imagery to measure the components of the varve; these include a terrigenous lamina formed by seasonal runoff from winter rains together with a diatomaceous lamina that records marine production during the spring and early summer. Spectral analysis of terrigenous and diatomaceous laminae thickness reveals significant periodicities of 3.1 and 8.4 yr in the terrigenous series; these are indistinguishable, within the frequency resolution of the spectra, from significant periodicities of 3.5 and 7.6 yr in the diatomaceous series. The 3.1 and 3.5 yr periodicities record El Nino modulation of coastal runoff and marine production; the 8.4 and 7.6 yr periodicities are consistent with modulation by strong to very strong El Nino events. This is supported by the results of cross-spectral analysis of the terrigenous and diatomaceous records, which reveal inverse or antiphase relationships at 3.5 and 7.6 yr. Our work adds to a body of evidence that suggests that El Nino has been a persistent feature of late Quaternary climate variability.

The low-latitude monsoon climate during Dansgaard–Oeschger cycles and Heinrich Events

During the last 100,000 years Dansgaard–Oeschger cycles (D/O cycles) and Heinrich Events have been the dominant signal of past climate variability over Greenland and the North Atlantic. The succession of stadials (cold) and interstadials (warm) associated with these cycles has been documented in records from the entire northern hemisphere, South America, New Zealand, Antarctica, the South Atlantic and the Southern Ocean. Evidently, climate forcing in the D/O band affects both hemispheres. The origin and cause of these teleconnected patterns is still unknown, even if a large proportion of the cooling in Europe and northern Asia during Heinrich Events is a meteorological response to cold surface water in the North Atlantic resulting from the surge of the Laurentian and Scandinavian ice sheets. But, this does not imply that the D/O cycles are a priori caused by the collapse of these large icesheets. A severe challenge to a primary origin from the northern ice sheet and North Atlantic comes from the observation that warming in Antarctica and the circumpolar current leads the North Atlantic changes by some 1500 years (Charles et al., 1996; Blunier et al., 1998). In the second part of the paper we investigate new deep sea records from the low-latitude monsoon system, mainly corroborating the result of Schulz et al. (1998) that the Indian monsoon showed D/O variability. The abundance of eolian dust (indicating continental humidity/aridity) in core 70KL from the Arabian Sea shows humid intervals which seem to correlate with temperature maxima in the Antarctic Vostok ice core. Apparently, the low-frequency, sub-Milankovitch variability of the monsoon is associated with the southern hemisphere. The D/O-scale component in the monsoonal climate, on the other hand, shows a succession of short humid intervals. The sequence is most closely comparable to the Greenland temperature record and to the stadial/interstadial succession in the Pacific Santa Barbara Basin ODP 893. In order to understand the global forcing of climate change in the D/O band, it appears necessary to quantify the phase relationships not only between D/O cycles in the polar ice cores (Bender et al., 1994; Blunier et al., 1998; Steig et al., 1998), but also between the low latitude Pacific, Indian Ocean and the high-latitude records.

Foraminifera in the Arabian Sea oxygen minimum zone and other oxygen-deficient settings: taxonomic composition, diversity, and relation to metazoan faunas

Previous work has shown that some foraminiferal species thrive in organically enriched, oxygen-depleted environments. Here, we compare `live’ (stained) faunas in multicorer samples (0–1 cm layer) obtained at two sites on the Oman margin, one located at 412 m within the oxygen minimum zone (OMZ) (O 2=0.13 ml l −1), the other located at 3350 m, well below the main OMZ (O 2∼3.00 ml l −1). While earlier studies have focused on the hard-shelled (predominantly calcareous) foraminifera, we consider complete stained assemblages, including poorly known, soft-shelled, monothalamous forms. Densities at the 412-m site were much higher (16,107 individuals.10 cm −2 in the >63-μm fraction) than at the 3350-m site (625 indiv.10 cm −2). Species richness (E(S 100)), diversity (H′, Fishers Alpha index) and evenness (J′) were much lower, and dominance (R1D) was higher, at 412 m compared with 3350 m. At 412 m, small calcareous foraminifera predominated and soft-shelled allogromiids and sacamminids were a minor faunal element. At 3350 m, calcareous individuals were much less common and allogromiids and saccamminids formed a substantial component of the fauna. There were also strong contrasts between the foraminiferal macrofauna (>300-μm fraction) at these two sites; relatively small species of Bathysiphon, Globobulimina and Lagenammina dominated at 412 m, very large, tubular, agglutinated species of Bathysiphon, Hyperammina, Rhabdammina and Saccorhiza were important at 3350 m. Our observations suggest that, because they contain fewer soft-shelled and agglutinated foraminifera, a smaller proportion of bathyal, low-oxygen faunas is lost during fossilization compared to faunas from well-oxygenated environments. Trends among foraminifera (>63 μm fraction) in the Santa Barbara Basin (590 and 610 m depth; O 2=0.05 and 0.15 ml l −1 respectively), and macrofaunal foraminifera (>300 μm) on the Peru margin (300–1250 m depth; O 2=0.02–1.60 ml l −1), matched those observed on the Oman margin. In particular, soft-shelled monothalamous taxa were rare and large agglutinated taxa were absent in the most oxygen-depleted (<0.20 ml l −1) stations. Foraminifera often outnumber metazoans (both meiofaunal and macrofaunal) in bathyal oxygen-depleted settings. However, although phylogenetically distant, foraminifera and metazoans exhibit similar population responses to oxygen depletion; species diversity decreases, dominance increases, and the relative abundance of the major taxa changes. The foraminiferal macrofauna (>300 μm) were 5 times more abundant than the metazoan macrofauna at 412 m on the Oman margin but 16 times more abundant at the 3350 m site. Among the meiofauna (63–300 μm), the trend was reversed; foraminifera were 17 times more abundant than metazoan taxa at 412 m but only 1.4 times more abundant at 3350 m. An abundance of food combined with oxygen levels which are not depressed sufficiently to eliminate the more tolerant taxa, probably explains why foraminifera and macrofaunal metazoans flourished at the 412-m site, perhaps to the detriment of the metazoan meiofauna.

Millennial reoccurrence of century‐scale abrupt events of East Asian Monsoon: A possible heat conveyor for the global deglaciation

High‐resolution sediment records from the South China Sea reveal a winter monsoon dominated glacial regime and a summer monsoon dominated Holocene regime during the last glacial cycle. A fundamental change between regimes occurred during deglaciation through a series of millennial reoccurrences of century‐scale changes in the East Asian monsoon (EAM) climate. These abrupt events centered at 17.0, 15.9, 15.5, 14.7, 13.5, 13.9, 13.3, 12.1, 11.5, and 10.7 14C ka correlate well with the millennial‐scale events in the Santa Barbara Basin and the Arabian Sea, i.e. a relationship between EAM and El Niño/Southern Oscillation systems. The abrupt increases in summer monsoon imply enhanced heat transport from low‐latitude sea area to the midlatitude/high‐latitude land area. The phase relationship between events of EAM and ice sheet may reflect a faster EAM response and a slower ice sheet response to the insolation change. A far‐reaching conclusion is that the EAM might have triggered the Northern Hemisphere deglaciation.

Dissolved sulfide distributions in the water column and sediment pore waters of the Santa Barbara Basin

Dissolved sulfide concentrations in the water column and in sediment pore waters were measured by square-wave voltammetry (nanomolar detection limit) during three cruises to the Santa Barbara Basin in February 1995, November–December 1995, and April 1997. In the water column, sulfide concentrations measured outside the basin averaged 3 ± 1 nM (n = 28) in the 0 to 600 m depth range. Inside the basin, dissolved sulfides increased to reach values of up to 15 nM at depths >400 m. A suite of box cores and multicores collected at four sites along the northeastern flank of the basin showed considerable range in surficial (<0.5 cm) pore-water sulfide concentrations: <0.008, 0.01, 0.02, to as much as 0.4 μM at the 340, 430, 550, and 590 m sites, respectively. At a core depth of 10 cm, however, pore–water sulfides exhibited an even wider range: 0.005, 0.05, 0.1, and 100 μM at the same sites, respectively. The sulfide flux into the deep basin, estimated from water-column profiles during three cruises, suggests a fairly consistent input of 100–300 nmole m−2 h−1. In contrast, sulfide fluxes estimated from pore-water sulfide gradients at the sediment water interface were much more variable (−4 to 13,000 nmole m−2 h−1). Dissolved silicate profiles show clear indications of irrigation at shallow sites (340 and 430 m) in comparison to deeper basin sites (550 and 590 m) with low (<10 μM) bottom-water dissolved-oxygen concentrations. Pore-water profiles indicate ammonia generation at all sites, but particularly at the deep-basin 590 m site with concentrations increasing with sediment depth to >400 μM at 10 cm. Decreases in water-column nitrate below the sill depth indicate nitrate consumption (−55 to −137 μmole m−2 h−1) similar to nearby Santa Monica Basin. Peaks in pore-water iron concentrations were generally observed between 2 and 5 cm depth with shallowest peaks at the 590 m site. These observations, including observations of the benthic microfauna, suggest that the extent to which the sulfide flux, sustained by elevated pore-water concentrations, reaches the water column may be modulated by the abundance of sulfide-oxidizing bacteria in addition to iron redox and precipitation reactions.

A 560-Year Record of Santa Ana Fires Reconstructed from Charcoal Deposited in the Santa Barbara Basin, California

Microscopic charcoal from varved Santa Barbara Basin sediments was used to reconstruct a 560-yr record (A.D. 1425 to 1985) of Santa Ana fires. Comparison of large (>3750 μm2) charcoal with documented fire records in the Santa Barbara Ranger District shows that high accumulations correspond to large fires (>20,000 ha) that occurred during Santa Ana conditions. The charcoal record reconstructed a minimum of 20 large fires in the Santa Barbara region during the study period. The average time between fires shows no distinct change across three different land use periods: the Chumash period, apparently characterized by frequent burning, the Spanish/Early American period with nominal fire control, and the 20th century with active fire suppression. Pollen data support the conclusion that the fire regime has not dramatically changed during the last 500 yr. Comparison of large charcoal particle accumulation rates and precipitation reconstructed from tree rings show a strong relationship between climate and fire history, with large fires consistently occurring at the end of wet periods and the beginning of droughts.

Benthic foraminifera of dysoxic sediments: chloroplast sequestration and functional morphology

Our recent surveys of dysoxic and anoxic sites reveal that many of the common foraminiferal inhabitants sequester chloroplasts. Such species include: Nonionella stella, which dominates the laminated sediments of the silled Santa Barbara Basin and comprises up to 82% of the living assemblage when [O 2] is below 2 μM (∼0.04 ml/l); the closely related species Nonionellina labradorica, which occurs in oxygen-depleted, silled fjords of Sweden; Stainforthia fusiformis, which dominates dysoxic sediments of Norwegian fjords; and Bulimina elegantissima, which is abundant in a shallow-water oil seep site supporting the filamentous, sulfide-oxidizing bacteria Beggiatoa. The literature contains examples of at least eight Elphidium species and one species from each of three other foraminiferal genera (i.e., Haynesina, Nonion, Reophax) that are known to sequester chloroplasts. These foraminifera are typically infaunal and/or may live under dysoxic conditions. Photosynthetic activity of the sequestered chloroplasts might provide oxygen to the host foraminifera, thereby enabling them to inhabit anoxic pore waters. However, given that most of the surveyed sites occur in the aphotic zone where light levels are too low to fuel photosynthesis, it is more likely that the host employs an as yet unidentified biochemical pathway associated with the sequestered chloroplasts. Additionally, these foraminifera have external test ornamentations that may facilitate separation of the chloroplasts from their algal prey. We discuss potential uses for these morphological features in interpreting the fossil record.

Sea-surface temperature anomalies associated with the 1997–1998 El Niño recorded in the oxygen isotope composition of planktonic foraminifera

Anomalously warm sea-surface temperatures and associated high rainfall propagated northward from the eastern equatorial Pacific along the western margin of North America during the 1997–1998 El Nino. We present data from the Guaymas Basin (Gulf of California) and the Santa Barbara Basin (Southern California Borderlands) that clearly demonstrate that the oxygen isotope composition of planktonic foraminifera accurately records the local sea-surface temperature changes related to the El Nino phenomenon. On the basis of this observation, the varved sediments accumulating in these basins should contain a detailed history of both the occurrence and intensity of past El Nino events.

Latest Quaternary North Pacific surface-water responses imply atmosphere-driven climate instability

Research Article| April 01, 1999 Latest Quaternary North Pacific surface-water responses imply atmosphere-driven climate instability Ingrid L. Hendy; Ingrid L. Hendy 1Department of Geological Sciences and Marine Science Institute, University of California, Santa Barbara, California 93106, USA Search for other works by this author on: GSW Google Scholar James P. Kennett James P. Kennett 1Department of Geological Sciences and Marine Science Institute, University of California, Santa Barbara, California 93106, USA Search for other works by this author on: GSW Google Scholar Geology (1999) 27 (4): 291–294. https://doi.org/10.1130/0091-7613(1999)027<0291:LQNPSW>2.3.CO;2 Article history first online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share MailTo Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Ingrid L. Hendy, James P. Kennett; Latest Quaternary North Pacific surface-water responses imply atmosphere-driven climate instability. Geology 1999;; 27 (4): 291–294. doi: https://doi.org/10.1130/0091-7613(1999)027<0291:LQNPSW>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract A full sequence of brief interstadials (Dansgaard-Oeschger [D-O] cycles) are recorded from 60 to 25 ka in Santa Barbara basin, California, Ocean Drilling Program Hole 893A, by planktonic foraminiferal isotopic and assemblage changes at unparalleled high resolution for the oceans. Synchronous climatic response between north Pacific surface waters and the Greenland ice sheet during D-O cycling is strongly indicated by remarkable similarities in speed, magnitude, and character of rapid oceanic and atmospheric reorganizations. Inferred sea-surface temperature warmings of as much as 5 °C within a few decades, and brief warming overshoots of as much as 3 °C suggest involvement of an atmospheric amplification. Top-down, in situ atmospheric warming of the ocean is implied by differential responses (partial decoupling) in the changes recorded in surface and thermoclinal waters. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Biotic response to late Quaternary rapid climate switches in Santa Barbara Basin: Ecological and evolutionary implications

Benthic foraminiferal assemblages from Santa Barbara Basin exhibit major faunal and ecological switches associated with late Quaternary millennial- to decadal-scale global climate oscillations. Repeated turnovers of entire faunas occurred rapidly (<40--400 yr) without extinction or speciation in conjunction with Dansgaard-Oeschger shifts in thermohaline circulation, ventilation, and climate, confirming evolutionary model predictions of Roy et al. Consistent faunal successions of dysoxic taxa during successive interstadials reflect the extreme sensitivity and adaptation of the benthic ecosystem to the rapid environmental changes that marked the late Quaternary and possibly other transitional intervals in the history of the Earth`s ocean-atmosphere-cryosphere system. These data support the hypothesis that broad segments of the biosphere are well adapted to rapid climate change.