Brian A. Haley

Is methane venting at the seafloor recorded by δ13C of benthic foraminifera shells

The research was supported by WCNURP grant PF806880 and by NSF grants OCE-9731157, OCE-9815186, and OCE-9906944. Curation of sediment cores at the OSU/NORCOR repository is supported by NSF.

Eastern Pacific Warm Pool paleosalinity and climate variability : 0–30 kyr

Multiproxy geologic records of δ18O and Mg/Ca in fossil foraminifera from sediments under the Eastern Pacific Warm Pool (EPWP) region west of Central America document variations in upper ocean temperature, pycnocline strength, and salinity (i.e., net precipitation) over the past 30 kyr. Although evident in the paleotemperature record, there is no glacial-interglacial difference in paleosalinity, suggesting that tropical hydrologic changes do not respond passively to high-latitude ice sheets and oceans. Millennial variations in paleosalinity with amplitudes as high as ∼4 practical salinity units occur with a dominant period of ∼3–5 ky during the glacial/deglacial interval and ∼1.0–1.5 ky during the Holocene. The amplitude of the EPWP paleosalinity changes greatly exceeds that of published Caribbean and western tropical Pacific paleosalinity records. EPWP paleosalinity changes correspond to millennial-scale climate changes in the surface and deep Atlantic and the high northern latitudes, with generally higher (lower) paleosalinity during cold (warm) events. In addition to Intertropical Convergence Zone (ITCZ) dynamics, which play an important role in tropical hydrologic variability, changes in Atlantic-Pacific moisture transport, which is closely linked to ITCZ dynamics, may also contribute to hydrologic variations in the EPWP. Calculations of interbasin salinity average and interbasin salinity contrast between the EPWP and the Caribbean help differentiate long-term changes in mean ITCZ position and Atlantic-Pacific moisture transport, respectively.

Development of a flow-through system for cleaning and dissolving foraminiferal tests

A novel flow-through method for cleaning and dissolving foraminiferal shells is presented. Using automated chromatographic equipment, the system chemically removes contaminant phases from the shells. The cleaned calcite is then dissolved in a stream of weak acid for minor and trace element analyses. The system operates at elevated temperature (80 °C) and pressures (850–900 psi) and is extremely reproducible. This method has several advantages compared to traditional batch method cleaning done in centrifuge vials. The most important of these is that nothing is lost from the flow-through system, permitting complete monitoring of and greater insight into the effects of cleaning and dissolution. Development of this method revealed that it is necessary to remove two contaminant phases from the shells: an oxide coating phase that is rich in Mn, Cd, and Mg, and a refractory phase that is rich in Ba and the rare earth elements (REEs). This cleaning is accomplished through the use of basic hydroxylamine and basic diethylene triamine pentaacetic acid (DTPA) solutions, respectively. Time-resolved analysis (TRA) of shell dissolution demonstrates that Orbulina shells are composed of high-Sr and low-Sr calcite types. Other minor (e.g., Mg) and trace (e.g., Cd, REEs, Ba) elements show the same distribution during dissolution as Sr. In Orbulina shells, the high-Sr (high-Mg) calcite always dissolves first, similar to observations of natural dissolution in the ocean. Consequently, this flow-through system may provide a simple solution to dissolution problems in proxy work. Further, since flow-through can provide several measurements of elemental composition for each calcite type, the method allows for true statistical evaluation of homogeneity during growth of the shell. Most significantly, this flow-through method fully cleans calcite, and provides information about the calcite and contaminant phases and thus should prove to be valuable in advancing geochemical proxies as tools for paleoceanographic investigations.

Beryllium isotopes in central Arctic Ocean sediments over the past 12.3 million years: Stratigraphic and paleoclimatic implications

The upper 200 m of the sediments recovered during IODP Leg 302, the Arctic Coring Expedition (ACEX), to the Lomonosov Ridge in the central Arctic Ocean consist almost exclusively of detrital material. The scarcity of biostratigraphic markers severely complicates the establishment of a reliable chronostratigraphic framework for these sediments, which contain the first continuous record of the Neogene environmental and climatic evolution of the Arctic region. Here we present profiles of cosmogenic 10Be together with the seawater-derived fraction of stable 9Be obtained from the ACEX cores. The down-core decrease of 10Be/9Be provides an average sedimentation rate of 14.5 ± 1 m/Ma for the uppermost 151 m of the ACEX record and allows the establishment of a chronostratigraphy for the past 12.3 Ma. The age-corrected 10Be concentrations and 10Be/9Be ratios suggest the existence of an essentially continuous sea ice cover over the past 12.3 Ma.

A major and long-term Pliocene intensification of the Mediterranean outflow, 3.5–3.3 Ma ago

Largely continuous millennial-scale records of benthic delta O-18, Mg/Ca-based temperature, and salinity variations in bottom waters were obtained from Deep Sea Drilling Project (DSDP) Site 548 (East Atlantic continental margin near Ireland, 1250 m water depth) for the period 3.7-3.0 Ma ago. High epsilon(Nd) values of -10.7 to -9 show that this site monitored changes in Mediterranean Outflow Water (MOW) throughout the mid-Pliocene. Bottom water variability at Ocean Drilling Progam (ODP) Site 978 (Alboran Sea, 1930 m water depth) provides a complementary record of MOW composition near its West Mediterranean source. Both sites show a singular and persistent rise in bottom water salinities by 0.7-1.4 psu, and in densities by similar to 1 kg m(-3) from 3.5 to 3.3 Ma ago, which is matched by an similar to 3 degrees C increase in bottom water temperature at Site 548. This event suggests the onset of strongly enhanced deep-water convection in the Mediterranean Sea and a related increase in MOW flow as a result of major aridification in the Mediterranean source region. In harmony with model suggestions, the enhanced MOW flow has possibly intensified Upper North Atlantic Deep Water formation.

Ocean Acidification Has Multiple Modes of Action on Bivalve Larvae.

Ocean acidification (OA) is altering the chemistry of the world’s oceans at rates unparalleled in the past roughly 1 million years. Understanding the impacts of this rapid change in baseline carbonate chemistry on marine organisms needs a precise, mechanistic understanding of physiological responses to carbonate chemistry. Recent experimental work has shown shell development and growth in some bivalve larvae, have direct sensitivities to calcium carbonate saturation state that is not modulated through organismal acid-base chemistry. To understand different modes of action of OA on bivalve larvae, we experimentally tested how pH, PCO2, and saturation state independently affect shell growth and development, respiration rate, and initiation of feeding in Mytilus californianus embryos and larvae. We found, as documented in other bivalve larvae, that shell development and growth were affected by aragonite saturation state, and not by pH or PCO2. Respiration rate was elevated under very low pH (~7.4) with no change between pH of ~ 8.3 to ~7.8. Initiation of feeding appeared to be most sensitive to PCO2, and possibly minor response to pH under elevated PCO2. Although different components of physiology responded to different carbonate system variables, the inability to normally develop a shell due to lower saturation state precludes pH or PCO2 effects later in the life history. However, saturation state effects during early shell development will carry-over to later stages, where pH or PCO2 effects can compound OA effects on bivalve larvae. Our findings suggest OA may be a multi-stressor unto itself. Shell development and growth of the native mussel, M. californianus, was indistinguishable from the Mediterranean mussel, Mytilus galloprovincialis, collected from the southern U.S. Pacific coast, an area not subjected to seasonal upwelling. The concordance in responses suggests a fundamental OA bottleneck during development of the first shell material affected only by saturation state.

Radiogenic isotope record of Arctic Ocean circulation and weathering inputs of the past 15 million years

Lead (Pb), neodymium (Nd), and strontium (Sr) isotopic analyses were carried out on sediment leachates (reflecting the isotope composition of past seawater) and digests of the bulk residues (reflecting detrital continental inputs) of Integrated Ocean Drilling Program (IODP) Leg 302 and core PS2185 from the Lomonosov Ridge (Arctic Ocean). Our records are interpreted to reflect changes in continental erosion and oceanic circulation, driven predominantly by tectonic forcing on million-year timescales in the older (pre-2 Ma) part of the record and by climatic forcing of weathering and erosion of the Eurasian continental margin on thousand-year timescales in the younger (post-2 Ma) part. These data, covering the past ∼15 Ma, show that continental inputs to the central Arctic Ocean have been more closely linked to glacial and hydrological processes occurring on the Eurasian margin than on continental North America and Greenland. The constancy of the detrital input signatures supports the early existence of an Arctic sea ice cover, whereas the major initiation of Northern Hemisphere glaciation at 2.7 Ma appears to have had little impact on the weathering regime of the Eurasian continental margin.

Online preconcentration ICP-MS analysis of rare earth elements in seawater

The rare earth elements (REEs) with their systematically varying properties are powerful tracers of continental inputs, particle scavenging intensity and the oxidation state of seawater. However, their generally low (∼pmol/kg) concentrations in seawater and fractionation potential during chemical treatment makes them difficult to measure. Here we report a technique using an automated preconcentration system, which efficiently separates seawater matrix elements and elutes the preconcentrated sample directly into the spray chamber of an ICP-MS instrument. The commercially available “seaFAST” system (Elemental Scientific Inc.) makes use of a resin with ethylenediaminetriacetic acid and iminodiacetic acid functional groups to preconcentrate REEs and other metals while anions and alkali and alkaline earth cations are washed out. Repeated measurements of seawater from 2000 m water depth in the Southern Ocean allows the external precision (2σ) of the technique to be estimated at <23% for all REEs and <15% for most. Comparison of Nd concentrations with isotope dilution measurements for 69 samples demonstrates that the two techniques generally agree within 15%. Accuracy was found to be good for all REEs by using a five point standard addition analysis of one sample and comparing measurements of mine water reference materials diluted with a NaCl matrix with recommended values in the literature. This makes the online preconcentration ICP-MS technique advantageous for the minimal sample preparation required and the relatively small sample volume consumed (7 mL) thus enabling large data sets for the REEs in seawater to be rapidly acquired.

Complete separation of rare earth elements from small volume seawater samples by automated ion chromatography: method development and application to benthic flux

A new Ion Chromatography–Inductively Coupled Plasma Mass Spectrometry (IC–ICP-MS) method is presented for measuring individual rare earth elements (REEs) in small volume (5 ml) seawater samples, with the goal of measuring pore water REEs. The method is shown to be accurate and reproducible for small volumes of a seawater reference standard within the determined precisions. The method has reasonable yield (75%), and, more importantly, is shown to not internally fractionate individual REEs. After describing the method, data from bottom, overlying and interfacial pore waters from four sites (three California margin, one Chile margin) are presented. These data show that there is a REE flux from sediments into bottom water. This flux ranges from 10−11 to 10−8 mol cm−2 ky−1 at these sites and is, therefore, on the same order as riverine input to the oceans. Benthic chamber samples support these flux estimates. When pore water and benthic chamber water are normalized to PAAS, the REE patterns can be characterized using three descriptors: the magnitude of the Ce anomaly (always negative), a “MREE bulge” and “HREE enrichment.” However, when normalized to bottom water, LREE>HREE and there is a significant positive Ce anomaly. These features generally support current understanding: that the REEs in the ocean are strongly influenced by organically driven processes. A key proviso is that the fluctuations in the Ce anomaly should be considered to be the net result of changes in dissolved La and Pr, and not mainly a function of Ce oxidation.

Bottoms up: Sedimentary control of the deep North Pacific Ocean's εNd signature

The ability to reconstruct past ocean currents is essential for determining ocean circulation9s role in global heat transport and climate change. Our understanding of the relationship between circulation and climate in the past allows us to predict the impact of future climate-driven circulation changes. One proposed tracer of past ocean circulation is the neodymium isotope composition (e Nd ) of ancient water masses. However, ambiguities in what governs the e Nd distribution in the modern ocean hamper interpretations of this tracer. Here we present e Nd values for marine pore fluids, sediments, and the overlying water column for three sites in the North Pacific. We find that ocean bottom water e Nd (e Nd BW ) in the northeast Pacific lies between the value expected for the water mass (–3.3) and the measured e Nd of sediment pore fluid (e Nd PW ; –1.8). Moreover, e Nd PW resembles the e Nd of the sediment. Combined, these findings are consistent with recent assessments that sediment pore fluids may be a major source of rare earth elements to the ocean and suggest that the benthic flux of Nd from pore fluids exerts the primary control over the deep ocean distribution of e Nd .