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2016
Farrington, JW, Burns KA, Leinen MS.  2016.  Synthesis and crosscutting topics. Oceanography. 29:204-213.   10.5670/oceanog.2016.84   AbstractWebsite

In recent years, there have been significant advances in fluid dynamics/physical oceanography, microbiology, weathering, remote sensing, and analytical chemistry as they pertain to the fate and effects of oil spills. Effects of the Deepwater Horizon oil spill on water column organisms and ecosystems have been difficult to ascertain. Laboratory experiments have expanded understanding of oil effects on phytoplankton and zooplankton. "Marine oil snow" has been identified as a significant factor in the fate of oil chemicals and their deposition with sediments. Oil chemicals and their effects on 24 km(2) of mud-benthic communities surrounding the well site, and in a few other areas, have lasted several years. Some deep-sea corals have also been affected for several years, and oil chemicals and their effects in heavily oiled marsh areas are projected to last a decade or longer. Lightly oiled marsh areas have recovered or are recovering. Research about use of dispersants highlights the need to update the 2005 National Research Council study of dispersant use on oil spills. Ongoing research should provide some closure for the issues of long-term effects on fisheries and marine mammals, and impacts on human health. Practical uses of this new knowledge are discussed briefly.

2015
Cai, W, Avery SK, Leinen M, Lee K, Lin X, Visbeck M.  2015.  Institutional coordination of global ocean observations. Nature Climate Change. 5:4-6.: Nature Publishing Group   10.1038/nclimate2482   Abstract

A sustainable global ocean observation system requires timely implementation of the framework for ocean observing. The recent Qingdao Global Ocean Summit highlighted the need for a more coherent institutional response to maintain an integrated ocean-observing system.

2012
Russell, LM, Rasch PJ, Mace GM, Jackson RB, Shepherd J, Liss P, Leinen M, Schimel D, Vaughan NE, Janetos AC, Boyd PW, Norby RJ, Caldeira K, Merikanto J, Artaxo P, Melillo J, Morgan MG.  2012.  Ecosystem impacts of geoengineering: a review for developing a science plan. Ambio. 41:350-369.   10.1007/s13280-012-0258-5   AbstractWebsite

Geoengineering methods are intended to reduce climate change, which is already having demonstrable effects on ecosystem structure and functioning in some regions. Two types of geoengineering activities that have been proposed are: carbon dioxide (CO2) removal (CDR), which removes CO2 from the atmosphere, and solar radiation management (SRM, or sunlight reflection methods), which reflects a small percentage of sunlight back into space to offset warming from greenhouse gases (GHGs). Current research suggests that SRM or CDR might diminish the impacts of climate change on ecosystems by reducing changes in temperature and precipitation. However, sudden cessation of SRM would exacerbate the climate effects on ecosystems, and some CDR might interfere with oceanic and terrestrial ecosystem processes. The many risks and uncertainties associated with these new kinds of purposeful perturbations to the Earth system are not well understood and require cautious and comprehensive research.

Murray, RW, Leinen M, Knowlton CW.  2012.  Links between iron input and opal deposition in the Pleistocene equatorial Pacific Ocean. Nature Geoscience. 5:270-274.   10.1038/ngeo1422   AbstractWebsite

Increases in overall marine primary productivity and export production in high-nutrient, low-chlorophyll regions of the ocean have, particularly during dry and dusty glacial periods, been hypothesized to be linked to the enhanced delivery of iron(1). In the modern ocean, iron availability limits production in high-nutrient, low-chlorophyll regions, and may be important in lower-nutrient settings as well(2). Here, we assess the relationship between productivity and iron in sedimentary records from the high-nutrient, low-chlorophyll region of the equatorial Pacific Ocean over the past million years. We find strong links between iron input, the export and burial of biogenic silica (opal) and total export production. Our data demonstrate that iron accumulation was more closely tied to the accumulation of opal than any other biogenic component, with high iron input associated with substantially increased opal sedimentation. The strong links between iron and opal accumulation over the past one million years are in agreement with the modern biogeochemical behaviour of iron and silica, and the response of the diatom community to their mutual availablity(3,4). Our data support earlier suggestions(1) of a biological response to iron delivery over geologic timescales.

2008
M, L.  2008.  Building relationships between scientists and business in ocean iron fertilization. Marine Ecology Progress Series. 364:251-256.   10.3354/meps07546   AbstractWebsite

The potential use of ocean iron fertilization (OIF) as a tool for either carbon reduction projects like those used to generate carbon credits or offsets, or for larger-scale mitigation to remove a significant percentage of CO2 from the atmosphere has interested the private sector. Scientists have highlighted the additional research that must be completed to understand the efficacy and impact of OIF at either scale. Carbon markets also place requirements on the nature of the credits generated if they are to be trusted and valued. The challenge for the future is to find effective ways for the science, business and carbon market communities to collaborate in ways that adhere to the high standards of scientific research. A code of conduct that recognizes the needs for scientific excellence and transparency, carbon market quality controls, and regulatory requirements like permitting can facilitate collaboration.

2000
Murray, RW, Knowlton C, Leinen M, Mix AC, Polsky CH.  2000.  Export production and terrigenous matter in the Central Equatorial Pacific Ocean during interglacial oxygen isotope Stage 11. Global and Planetary Change. 24:59-78.   10.1016/s0921-8181(99)00066-1   AbstractWebsite

This study addresses changes in the absolute magnitude and spatial geometry of particle flux and export production in a meridional transect across the central equatorial Pacific Ocean's upwelling system during oxygen isotope Stage II and Stage 12 and compares these time periods to the current Holocene interglacial system. Temporal and spatial variability in several chemical proxies of export production, and in particular the distributions of Ba, scavenged Al, and P, are studied in a suite of sediment cores gathered along a cross-equator transect at 5 degrees S, 2 degrees S, 0 degrees, 2 degrees N, and 4 degrees N. Because this latitudinal range preserves strong gradients in biogenic particle flux in the modern equatorial Pacific Ocean, we are able to assess variations in the relative magnitude of export production as well as the meridional width of the equatorial system through the late Quaternary glacial/interglacial cycles. During interglacial oxygen isotope Stage Ii the chemical proxies each indicate lower particle flux and export production than during Stage 12. These records are consistent throughout the transect during this time period, but geographic narrowing (during the interglacial) and widening (during the glacial) of the meridional gradient also occurs. Although carbonate concentration varies dramatically through glacial/interglacial cycles at all latitudes studied, the productivity proxies record only minimal glacial/interglacial change at 5 degrees S and 4 degrees N, indicating that the carbonate minima at these latitudes is controlled dominantly by dissolution rather than production. The chemical data indicate that although the spatial geometry of the system during Stages 11 and 12 indicates maximum productivity at the equator during both glacial and interglacial conditions, the absolute magnitude of export production integrated from 5 degrees S to 4 degrees N during Stage 11 was 25-50% less than during Stage 12, and also was 25-50% less than it is now. (C) 2000 Elsevier Science B.V. All rights reserved.

Murray, RW, Knowlton C, Leinen M, Mix AC, Polsky CH.  2000.  Export production and carbonate dissolution in the central equatorial Pacific Ocean over the past 1 Myr. Paleoceanography. 15:570-592.   10.1029/1999pa000457   AbstractWebsite

In order to quantify changes in export production and carbonate dissolution over the past 1 Myr in the central equatorial Pacific Ocean we analyzed Ba, P, Al, Ti, and Ca in 1106 samples from five piston cores gathered from 5 degreesS to 4 degreesN at 140 degreesW. We focused on Ba/Ti, Al/Ti, and P/Ti ratios as export proxies and employed areally integrated time slice as well as time series strategies. Carbonate maxima from 0-560 kyr are characterized by 15-30% seater export than carbonate minima. The increases in export fall on glacial delta (18)O transitions rather than glacial maxima. From 560-800 kyr, overlapping with the mid-Pleistocene transition, there is a very large increase in total export yet no glacial-interglacial variability. The highest latitudes (5 degreesS and 4 degreesN) record minimal absolute export change from glacials to interglacials and yet record the most extreme minima in percent CaCO(3), indicating that carbonate records there are dominated by dissolution, whereas near the equator they are more influenced by changes in export.

1998
Arnold, E, Merrill J, Leinen M, King J.  1998.  The effect of source area and atmospheric transport on mineral aerosol collected over the North Pacific Ocean. Global and Planetary Change. 18:137-159.   10.1016/s0921-8181(98)00013-7   AbstractWebsite

Aerosol samples collected on two North Pacific cruises were analyzed for rock-magnetic properties, grain size and < 2 mu m and 2-20 mu m mineralogy. These sedimentological results were compared with isentropic air mass trajectories in order to study the effects of source region and atmospheric transport on the mineral aerosol. The results indicate that there are differences in the aerosol composition and grain size for two broad source regions. Aerosols which originate from west of the Pacific an characterized by abundant, fine-grained aerosol, which has a high coercivity magnetic composition, and is relatively enriched in kaolinite. Aerosols originating from continents to the north and east of the Pacific basin are much less abundant, contain coarse-grained material with a low coercivity magnetic component, and the mineralogy is relatively enriched in plagioclase. Comparison of the mineral aerosol from Asia with atmospheric transport time indicated that the concentration of the mineral aerosol decreases with increasing transport time. The mineral aerosol is compositionally fractionated as it moves away from the continental source region, with a relative decrease in the primary minerals quartz and plalagioclase and an increase in the smectite, illite and chlorite concentration with increasing transport time. (C) 1998 Elsevier Science B.V. All rights reserved.

1997
Schroeder, JO, Murray RW, Leinen M, Pflaum RC, Janecek TR.  1997.  Barium in equatorial Pacific carbonate sediment: Terrigenous, oxide, and biogenic associations. Paleoceanography. 12:125-146.   10.1029/96pa02736   AbstractWebsite

We have analyzed carbonate sediment from Ocean Drilling Program Site 850 (equatorial Pacific Ocean) in order to assess the changing effects of sedimentation style on Ba accumulation through time. Formed along the East Pacific Rise similar to 12 m.y. ago at 1 degrees-2 degrees S and now located at 1.3 degrees N, Site 850 has experienced many changes through its northwesterly migration, including a crossing of the equator at similar to 4 Ma. We divide sedimentation into three stages (phases I, II, and III; with phase III being youngest) according to geographic position, lithostratigraphy, and bull; accumulation rate. Of greatest importance are contrasts between phase II (7.5-4.0 m.y. ago) and phase III (4.0-0 m.y. ago). Phase II includes the previously described ''biogenic bloom'' as well as the depositional record of elevated productivity near the equator. In phase II the accumulation of Ba shows the strongest correlation with the accumulation of CaCO3 (r(2) = 0.69), opal (r(2) = 0.44), and C-org (r(2) = 0.41) compared with elsewhere through the sequence, although the correlation with terrigenous accumulation is also very strong (r(2) = 0.63). In phase III, which records deposition in the northern hemisphere and is thus closer to terrigenous input at the Intertropical Convergence Zone (ITCZ), there are no statistically significant correlations between the accumulations rates of Ba and CaCO3, Ba and opal, and Ba and C-org. Most significantly, through phase III the Ba accumulation rate is extremely strongly tied to terrigenous accumulation (r(2) = 0.89), which is the strongest correlation of any in our database, and to the accumulation of Fe-excess (r(2) = 0.74), which we use to track the Fe-oxide component. Cross-equator surface sediment transects have previously indicated that beneath the ITCZ there is a pronounced local maximum in Ba accumulation, and the strong tie between Ba and terrigenous accumulation and associated Fe-oxides at Site 850 also corresponds with its tectonic migration toward the ITCZ. We conclude that the putative link between Ba accumulation and export production may be obscured by changes in particle composition even within a dominantly biogenic sedimentary regime, as well as by early diagenetic transfer between phases, and that the non-barite elemental Ba inventory may complicate the use of elemental Ba as a quantitative proxy for barite in the bulk sediment.

Berelson, WM, Anderson RF, Dymond J, DeMaster D, Hammond DE, Collier R, Honjo S, Leinen M, McManus J, Pope R, Smith C, Stephens M.  1997.  Biogenic budgets of particle rain, benthic remineralization and sediment accumulation in the equatorial Pacific. Deep-Sea Research Part Ii-Topical Studies in Oceanography. 44:2251-2282.   10.1016/s0967-0645(97)00030-1   AbstractWebsite

Budgets of organic C (C-org), CaCO3 and opal have been constructed for the Pacific equatorial region at 140 degrees W between 5 degrees N and 5 degrees S. Measurements of the rain and benthic remineralization rate of biogenic materials have been adjusted and normalized to account for sampling biases. Sea surface temperature serves as a master variable in normalizing sediment trap and benthic remineralization data to average conditions. The rain and remineralization rates for C(o)rg are nearly equal: 0.40+/-0.05 and 0.46+/-0.06 mmol m(-2) d(-1), respectively;thus only a minor fraction of this constituent is buried. Rain and dissolution rates for biogenic opal are similarly balanced respectively; thus only a minor fraction of this constituent is buried. Rain and dissolution rates (0.38+/-0.06 and 0.36+/-0.01 mmol m(-2) d(-1)) and consistent with the value for opal burial (0.03+/-0.004). The CaCO3 budget appears to have changed during the Holocene. The best estimates of modern CaCO3 dissolution (0.58+/-0.03 mmol m(-2) d(-1)) and rain rate (0.61+/-0.06) are consistent with Th-230-normalized carbonate accumulation rates for the late Holocene (0.1 mmol m(-2) d(-1)). However, the balance between dissolution and rain is not consistent with early Holocene carbonate accumulation (0.3 mmol m(-2) d(-1)), and this imbalance suggests: 1)a recent increase in the rate of CaCO3 dissolution on the sea floor, or 2) a decrease in the rain rate of carbonate particles. Modeling Th-230 profiles in sediments from this region define the last 3000 years as the duration of increased dissolution or decreased particle rain. Pa-231/Th-230 ratios in sediments indicate that particle rain rates have remained constant or possibly increased slightly through the Holocene. Two potential causes for increased dissolution were investigated; a change in deep water carbonate saturation or a change in C-org/CaCO3 rain ratios. A model describing carbonate dissolution as a function of the degree of undersaturation and the amount of organic carbon oxidation within sediments indicates that the recent increase in dissolution is more likely due to changes in bottom water chemical composition. We propose that Pacific Ocean bottom water carbonate ion concentration has decreased by 10-15 mu M over the last 3000 years. (C) 1998 Elsevier Science Ltd. All rights reserved.

1996
LaMontagne, RW, Murray RW, Wei KY, Leinen M, Wang CH.  1996.  Decoupling of carbonate preservation, carbonate concentration, and biogenic accumulation: A 400-kyr record from the central equatorial Pacific Ocean. Paleoceanography. 11:553-562.   10.1029/96pa02249   AbstractWebsite

In order to investigate the paleoceanographic record of dissolution of calcium carbonate (CaCO3) in the central equatorial Pacific Ocean, we have studied the relationship between three indices of foraminiferal dissolution and the concentration and accumulation of CaCO3, opal, and C-org in Core WEC8803B-GC51 (1.3 degrees N, 133.6 degrees W; 4410 m). This core spans the past 413 kyr of deposition and moved in and out of the lysoclinal transition zone during glacial-interglacial cycles of CaCO3 production and dissolution. The record of dissolution intensity provided by foraminiferal fragmentation, the proportion of benthic foraminifera, and the foraminiferal dissolution index consistently indicates that the past corrosion of pelagic CaCO3 in the central equatorial Pacific does not vary with the observed sedimentary concentration of CaCO3. Although there is a weak low-frequency variation (similar to 100 kyr) in dissolution intensity, it is unrelated to sedimentary CaCO3 concentration. There are many shorter-lived episodes where high CaCO3 concentration is coincident with poor foraminiferal preservation, and where, conversely, low CaCO3 concentration is coincident with superb foraminiferal preservation. Spectral analyses indicate that dissolution maxima consistently lagged glacial maxima (manifest by the SPECMAP delta(18)O stack) in the 100-kyr orbital band. Additionally, there is no relationship between dissolution and the accumulation of biogenic opal or C-org or between dissolution and the burial ratio of C-org/C-INorg (calculated from C-org and CaCO3). Because previous studies of this core strongly suggest that surface water productivity varied closely with CaCO3 accumulation, both the mechanistic decoupling of carbonate dissolution from CaCO3 concentration (and from biogenic accumulation) and the substantial phase shift between dissolution and global glacial periodicity effectively obscure any simple link between export production, CaCO3 concentration, and dissolution of sedimentary CaCO3.

Murray, RW, Leinen M.  1996.  Scavenged excess aluminum and its relationship to bulk titanium in biogenic sediment from the central equatorial Pacific Ocean. Geochimica Et Cosmochimica Acta. 60:3869-3878.   10.1016/0016-7037(96)00236-0   AbstractWebsite

We present results from chemical analyses of Aland Ti in surface sediment sampled along two cross-Equator latitudinal transects at 135W and 140W in the central equatorial Pacific Ocean. Although traditionally both Al and Ti are considered to reside exclusively within terrigenous phases in marine sediment, these sediments present extremely high Al/Ti ratios that are several times that of average shale and other potential crustal sources. A sharp maximum in Al/Ti is observed slightly south of the Equator, where sedimentary bulk accumulation rate (BAR) is also highest (reflecting elevated productivity in the overlying water caused by surface water divergence). Bulk Al/Ti decreases sharply away (+/- 2 degrees latitude) to near crustal values at similar to 4 degrees north and south. The latitudinal profiles of Al/Ti are entirely unrelated to the concentration of the biogenic components as well as to the absolute accumulation of Al and Ti. These results indicate the presence of a significant scavenged component of Al sourced directly from seawater during particle settling. The data from the two transects analytically and oceanographically confirms our earlier work that was based on the single 135W transect. Calculations of Al-excess indicate that the highest Al/Ti ratios correspond to similar to 50% of the total Al being unsupported by the small amount of terrigenous phases present. These results are consistent with previous and ongoing studies of biogenic sediment, suspended particulate matter, and sediment trap material. Quantitative use of Al as an index of terrigenous material may, therefore, lead to an overstimation, by a factor of two, of the true terrigenous load in marine sediment, sedimentary rock, and settling particles. Because bulk Al/Ti appears to respond to sedimentary BAR, which in biogenic regimes is linked to surface water productivity, downcore records of Al/Ti in biogenic sediment may track productivity changes through time. Such Al/Ti proxy records may be applicable in sediment of all ages, unlike radionuclide tracers which are limited by radioactive decay to use over the past hundreds of kyr.

1995
Murray, RW, Leinen M, Murray DW, Mix AC, Knowlton CW.  1995.  Terrigenous Fe input and biogenic sedimentation in the glacial and interglacial equatorial Pacific Ocean. Global Biogeochemical Cycles. 9:667-684.   10.1029/95gb02833   AbstractWebsite

Many ocean regions important to the global carbon budget, including the equatorial Pacific Ocean, have low chlorophyll concentrations despite high levels of conventional nutrients. iron may instead be the limiting nutrient, and elevated input of terrigenous Fe during windy glacial episodes has been hypothesized to stimulate oceanic productivity through time and thus regulate the oceanic and atmospheric CO2 balance. To test whether particulate Fe input is related to the accumulation of biogenic matter in one important low chlorophyll-high nutrient area, that is, the equatorial Pacific Ocean, we present results from a suite of sediment cores that collectively record biogenic deposition through the last six glacial-interglacial cycles (similar to 600,000 years). Our data set includes new chemical data on total Fe, terrigenous, and biogenic components in three cores as well as previously published mineralogic records of eolian input to the region. Chemical, spectral, and stratigraphic analysis indicates that (1) terrigenous input to the region shows no consistent pattern of either glacial or interglacial maxima, (2) the accumulation of particulate Fe is closely related to the accumulation of terrigenous matter (Linear r(2) = 0.81 - 0.98), (3) there are no coherent spectral relationships between Fe input and glacial periodicity (i.e., delta(18)O) in any of the orbital frequency bands, (4) the linear and cross-spectral correlations between Fe or eolian input and CaCO3 concentration are most Commonly the strongest observed relationships between Fe and any biogenic component, yet indicate a largely inverse pattern, with higher Fe being associated with low CaCO3, (5) there is no consistent linear r(2) correlation or spectral coherence between the accumulation of Fe and that of CaCO3, C-org, Or opal. Thus in total there is no relationship between terrigenous Fe input and sedimentary sequestering of carbon. Additionally, although we cannot specifically address the potential for changes in solubility of the terrigenous fraction that may be driven by a terrigenous compositional change, the Fe/Ti ratio (which monitors first-order mineralogic changes) records only slight variations that also are linearly and spectrally unrelated to glacial periodicity, the bulk Fe flux, and the accumulation of any biogenic component. Finally, we find that the paleoceanographic flux of Fe is several order-of-magnitudes larger than modem observations of eolian Fe input, suggesting that the long-term importance of Fe input by dust storms (which deliver Fe on the order of the sedimentary burial) may be underestimated. The removal of particulate terrigenous Fe from the recently discovered source within the Equatorial Undercurrent, however, remains unquantified and may also prove significant.

Arnold, E, Leinen M, King J.  1995.  Paleoenvironmental variation based on the mineralogy and rock-magnetic properties of sediment from Sites 885 and 886. Proceedings of the Ocean Drilling Program, Scientific Results. 145:241-245.   10.2973/odp.proc.sr.145.113.1995   Abstract

Variation in the mineralogy and rock magnetic properties of Sites 885 and 886 sediment can be explained by changing environmental conditions in the sediment source areas and sediment column. Climatic variations produce changes in the mineralogy and magnetics at these sites consistent with aridification of the Asian source area and cooling forced by tectonic activity. Asian aridification is noted by gradual reduction of a kaolinite-rich mineral assemblage from the late Miocene to an abrupt mineralogy change at 3.8 Ma to a chlorite- and illite-rich mineral assemblage. At the same time, the eolian mass accumulation rate and ferrimagnetic grain size increases. This event precedes the onset of Asian loess deposition by over 1 m.y., but it is consistent with a coupled environmental mechanism that explains the rapid onset of loess sedimentation at 2.5 Ma. Both the mineralogy and rock magnetics are overprinted with a diagenetic signal that suggests the sediments proximal to Sites 885 and 886 may have been suboxic to anoxic in the early Pliocene.

1994
Leinen, M, Prospero JM, Arnold E, Blank M.  1994.  Mineralogy of aeolian dust reaching the North Pacific Ocean: 1. Sampling and analysis. Journal of Geophysical Research-Atmospheres. 99:21017-21023.   10.1029/94jd01735   AbstractWebsite

The mineral composition of the <2-mu m (clay) and 2- to 20-mu m (silt) size fractions of aerosol particles collected near the margins of the North Pacific Ocean was determined by X ray diffraction analysis. Although the same mineral phases are present in the two size fractions, there are significant differences in the quartz, plagioclase, and kaolinite concentrations. North Pacific aerosols are primarily composed of illite in both size fractions in addition to kaolinite in the <2-mu m size class and quartz and plagioclase in the 2- to 20-mu m size class. Quartz and plagioclase are present in significantly higher amounts in the 2- to 20-mu m size fraction, while kaolinite is greater in the <2-mu m size class. Western North Pacific aerosol particles contain significantly higher <2-mu m quartz than samples collected in the east, and eastern North Pacific aerosols have significantly higher concentrations of <2-mu m smectite than those from the west.

Merrill, J, Arnold E, Leinen M, Weaver C.  1994.  Mineralogy of aeolian dust reaching the North Pacific Ocean: 2. Relationship of mineral assemblages to atmospheric transport patterns. Journal of Geophysical Research-Atmospheres. 99:21025-21032.   10.1029/94jd01734   AbstractWebsite

Atmospheric dust particles actually comprise a small number of mineral assemblages. We determined the composition of these assemblages and their geographic distribution by statistical analysis of mineralogy data. Air mass trajectory analysis was used to identify transport paths and possible source regions for these samples. Three types of trajectories are most common, and each displays different proportions of four mineral assemblages. The first indicates outflow of air from central Asia and is associated with an illite-rich mineralogy. The second type comprises trajectories which include low-altitude transport over the Japanese islands, for mixed mineralogies which contained a small amount of the illite-rich end-member. The third type is made up of trajectories crossing the North American continent and is present exclusively in the eastern North Pacific area. There is a mixed mineralogy associated with these trajectories. Our results suggest that both source area mineralogy and transport pathway contribute to the compositional variability of the mineral aerosol at a given location. The results presented here show that event-specific meteorological data can be useful in understanding spatial patterns of eolian transport.

1993
Murray, RW, Leinen M.  1993.  Chemical transport to the seafloor of the equatorial Pacific Ocean across a latitudinal transect at 135°W: Tracking sedimentary major, trace, and rare earth element fluxes at the Equator and the Intertropical Convergence Zone. Geochimica Et Cosmochimica Acta. 57:4141-4163.   10.1016/0016-7037(93)90312-k   AbstractWebsite

We have analyzed the major, trace, and rare earth element composition of surface sediments collected from a transect across the Equator at 135-degrees-W longitude in the Pacific Ocean. Comparing the behavior of this suite of elements to the CaCO3, opal, and C(org) fluxes (which record sharp maxima at the Equator, previously documented at the same sampling stations) enables us to assess the relative significance of the various pathways by which trace elements are transported to the equatorial Pacific seafloor. The (1) high biogenic source at the Equator, associated with equatorial divergence of surface water and upwelling of nutrient-rich water, and (2) high aluminosilicate flux at 4-degrees-N, associated with increased terrigenous input from elevated rainfall at the Intertropical Convergence Zone (ITCZ) of the tradewinds, are the two most important fluxes with which elemental transport is affiliated. The biogenic flux at the Equator transports Ca and Sr structurally bound to carbonate tests and Mn primarily as an adsorbed component. Trace elements such as Cr, As, Pb, and the REEs are also influenced by the biogenic flux at the Equator, although this affiliation is not regionally dominant. Normative calculations suggest that extremely large fluxes of Ba and P at the Equator are carried by only small proportions of barite and apatite phases. The high terrigenous flux at the ITCZ has a profound effect on chemical transport to the seafloor, with elemental fluxes increasing tremendously and in parallel with Ti. Normative calculations, however, indicate that these fluxes are far in excess of what can be supplied by lattice-bound terrigenous phases. The accumulation of Ba is greater than is affiliated with biogenic transport at the Equator, while the P flux at the ITCZ is only 10% less than at the Equator. This challenges the common view that Ba and P are essentially exclusively associated with biogenic fluxes. Many other elements (including Mn, Pb, As, and REEs) also record greater accumulation beneath the ITCZ than at the Equator. Thus, adsorptive scavenging by terrigenous particulate matter, or phases intimately associated with them, appears to be an extremely important process regulating elemental transport to the equatorial Pacific seafloor. These findings emphasize the role of vertical transport to the sediment, and provide additional constraints on the paleochemical use of trace elements to track biogenic and terrigenous fluxes.

Murray, RW, Leinen M, Isern AR.  1993.  Biogenic flux of Al to sediment in the central equatorial Pacific Ocean: Evidence for increased productivity during glacial periods. Paleoceanography. 8:651-670.   10.1029/93pa02195   AbstractWebsite

We examined the flux of Al to sediment accumulating beneath the zone of elevated productivity in the central equatorial Pacific Ocean, along a surface sediment transect at 135-degrees-W as well as downcore for a 650 kyr record at 1.3-degrees-N, 133.6-degrees-W. Across the surface transect, a pronounced, broadly equatorially symmetric increase in Al accumulation is observed, relative to Ti, with Al/Ti ratios reaching values 3-4 times that of potential detrital sources. The profile parallels biogenic accumulation and the modeled flux of particulate Th-234, suggesting rapid and preferential adsorptive removal of Al from seawater by settling biogenic particles. Normative calculations confirm that most Al is unsupported by the terrigenous fraction. The observed distributions are consistent with previous observations of the relative and absolute behavior of Al and Ti in seawater, and we can construct a reasonable mass balance between the amount of seawater-sourced Al retained in the sediment and the amount of seawater Al available in the overlying column. The close tie between Al/Ti and biogenic accumulation (as opposed to concentration) emphasizes that biogenic sedimentary Al/Ti responds to removal-transport phenomena and not bulk sediment composition. Thus, in these sediments dominated by the biogenic component, the bulk Al/Ti ratio reflects biogenic particle flux, and by extension, productivity of the overlying seawater. The downcore profile of Al/Ti at 1.3-degrees-N displays marked increases during glacial episodes, similar to that observed across the surface transect, from a background value near Al/Ti of average upper crust. The excursions in Al/Ti are stratigraphically coincident with maxima in both bulk and CaCO3 accumulation and the excess Al appears to not be preferentially affiliated with opaline or organic phases. Consistent with the similar behavioral removal of Al and Th-234, the latter of which responds to the total particle flux, the Al flux reflects carbonate accumulation only because carbonate comprises the dominant flux in these particular deposits. These results collectively indicate that (1) Al in biogenic sediment and settling biogenic particles is strongly affected by a component adsorbed from seawater. Therefore, the common tenet that Al is dominantly associated with terrestrial particulate matter, and the subsequent use of Al distributions to calculate the abundance and flux of terrestrial material in settling particles and sediment, needs to be reevaluated. (2) The Al/Ti ratio in biogenic sediment can be used to trace the productivity of the overlying water, providing a powerful new paleochemical tool to investigate oceanic response to climatic variation. (3) The close correlation between the Al/Ti productivity signal and carbonate maxima downcore at 1.3-degrees-N suggests that the sedimentary carbonate maxima in the central equatorial Pacific Ocean record increased productivity during glacial episodes.

Kyte, FT, Leinen M, Heath GR, Zhou L.  1993.  Cenozoic sedimentation history of the central North Pacific: Inferences from the elemental geochemistry of core LL44-GPC3. Geochimica Et Cosmochimica Acta. 57:1719-1740.   10.1016/0016-7037(93)90109-a   AbstractWebsite

The concentrations of thirty-nine elements in 324 samples show large variations in sediments down the 24.3 m length of LL44-GPC3, a piston core of pelagic clay from the central North Pacific (30-degrees 19'N, 157-degrees 49.9'W) that contains a relatively continuous record of sedimentation since the late Cretaceous. Strong interelement correlations identify five groups of elements whose variance is related and which we interpret to represent porewater salts, silicates, biogenic phosphates, and hydrothermal and hydrogenous oxyhydroxide precipitates. Interelement ratios, when combined with mineralogical, sedimentological, and site-backtrack data, indicate that at least five distinct sources contributed to the aluminosilicate fraction of the sediments in the core. Eight endmember sediment source components (two eolian, two volcanic, two biogenous, one hydrothermal, and one hydrogenous) are modeled and quantified by total inversion. Accumulation rates of these components and of thirty-nine elements vary dramatically for stratigraphically defined intervals within the Cenozoic. Continuous accumulation-rate profiles based on a model combining stratigraphic data and an assumed constant flux of hydrogenous Co yield a general sedimentation model that reflects variations in the sedimentary environment as the LL44-GPC3 site migrated from near the equator in the late Cretaceous to its present location north of Hawaii.

1992
Murray, JW, Leinen M, Feely RA, Toggweiler JR, Wannikhof R.  1992.  EqPac: A Process Study in the Central Equatorial Pacific. Oceanography. 5:134-142.   10.5670/oceanog.1992.01   Abstract

EqPac is the United States-Joint Global Ocean Flux Study (US-JGOFS) process study in the central equatorial Pacific. The first EqPac cruises sailed in January 1992 during a moderately strong El Niño. This was fortuitous for our studies of chemical and biological distributions because El Niño events are difficult to predict, and the lead time for a project of this size is long. There was virtually no previous upper-water-column chemical or biological data for El Niño conditions in the central equatorial Pacific. Now an El Niño has been studied in considerable detail, and it will be easy to sample the extremes in environmental conditions by sampling non-El Niño conditions (including La Niña) in 1993 and the years thereafter. The implementation of EqPac illustrates how difficult it is to mount a large-scale interdisciplinary study of the ocean when the interannual variability is large. - See more at: http://www.tos.org/oceanography/archive/5-3_murray.html#sthash.mMrZYsdk.dpuf

Feldman, GC, Murray JW, Leinen MW.  1992.  Use of the Coastal Zone Color Scanner for EqPac Planning. Oceanography. 5:143-145.   10.5670/oceanog.1992.02   Abstract

One of the most interesting and useful pieces of data for basin-scale planning of EqPac (Leinen and Murray, 1990; Murray et al., 1992, this issue) was the satellite-derived ocean-color data set acquired by the Coastal Zone Color Scanner (CZCS) (Feldman et al., 1989). To accomplish EqPac goals we need a more precise estimate of the temporal and spatial distributions of phytoplankton biomass and primary production. Traditional shipboard sampling techniques by themselves are not sufficient to meet these needs on global, or for that matter, basin scales. However, satellite observations of ocean color can provide reliable estimates of marine phytoplankton biomass at the relevant time and space scales. - See more at: http://www.tos.org/oceanography/archive/5-3_feldman.html#sthash.JJclwPmO.dpuf

1991
Martin, WR, Bender M, Leinen M, Orchardo J.  1991.  Benthic organic carbon degradation and biogenic silica dissolution in the central equatorial Pacific. Deep-Sea Research Part a-Oceanographic Research Papers. 38:1481-1516.   10.1016/0198-0149(91)90086-u   AbstractWebsite

Shipboard whole-core squeezing was used to measure pore water concentration vs depth profiles of NO3-, O2 and SiO2 at 12 stations in the equatorial Pacific along a transect from 15-degrees-S to 11-degrees-N at 135-degrees-W. The NO3- and SiO2 profiles were combined with fine-scale resistivity and porosity measurements to calculate benthic fluxes. After using O2 profiles, coupled with the NO3-profiles, to constrain the C:N of the degrading organic matter, the NO3- fluxes were converted to benthic organic carbon degradation rates. The range in benthic organic carbon degradation rates is 7-30-mu-mol cm-2 y-1, with maximum values at the equator and minimum values at the southern end of the transect. The zonal trend of benthic degradation rates, with its equatorial maximum and with elevated values skewed to the north of the equator, is similar to the pattern of primary production observed in the region. Benthic organic carbon degradation is 1-2% of primary production. The range of benthic biogenic silica dissolution rates is 6.9-20-mu-mol cm-2 y-1, representing 2.5-5% of silicon fixation in the surface ocean of the region. Its zonal pattern is distinctly different from that of organic carbon degradation: the range in the ratio of silica dissolution to carbon degradation along the transect is 0.44-1.7 mol Si mol C-1, with maximum values occurring between 12-degrees-S and 2-degrees-S, and with fairly constant values of 0.5-0.7 north of the equator. A box model calculation of the average lifetime of the organic carbon in the upper 1 cm of the sediments, where 80 +/- 11% of benthic organic carbon degradation occurs, indicates that it is short: from 3.1 years at high flux stations to 11 years at low flux stations. The reactive component of the organic matter must have a shorter lifetime than this average value. In contrast, the average lifetime of biogenic silica in the upper centimeter of these sediments is 55 +/- 28 years, and shows no systematic variations with benthic flux.

1990
Taylor, B, Brown G, Fryer P, Gill JB, Hochstaedter AG, Hotta H, Langmuir CH, Leinen M, Nishimura A, Urabe T.  1990.  Alvin-SeaBeam studies of the Sumisu Rift, Izu-Bonin arc. Earth and Planetary Science Letters. 100:127-+.   10.1016/0012-821x(90)90181-v   AbstractWebsite

Bimodal volcanism, normal faulting, rapid sedimentation, and hydrothermal circulation characterize the rifting of the Izu-Bonin arc at 31°N. Analysis of the zigzag pattern, in plan view, of the normal faults that bound Sumisu Rift indicates that the extension direction (080° ± 10°) is orthogonal to the regional trend of the volcanic front. Normal faults divide the rift into an inner rift on the arc side, which is the locus for maximum subsidence and sedimentation, and an outer rift further west. Transfer zones that link opposing master faults and/or rift flank uplifts further subdivide the rift into three segments along strike. Volcanism is concentrated along the ENE-trending transfer zone which separates the northern and central rift segments. The differential motion across the zone is accommodated by interdigitating north-trending normal faults rather than by ENE-trending oblique-slip faults. Volcanism in the outer rift has built 50–700 m high edifices without summit craters whereas in the inner rift it has formed two multi-vent en echelon ridges (the largest is 600 m high and 16 km long). The volcanism is dominantly basaltic, with compositions reflecting mantle sources little influenced by arc components. An elongate rhyolite dome and low-temperature hydrothermal deposits occur at the en echelon step in the larger ridge, which is located at the intersection of the transfer zone with the inner rift. The chimneys, veins, and crusts are composed of silica, barite and iron oxide, and are of similar composition to the ferruginous chert that mantles the Kuroko deposits. A 1.2-km transect of seven alvin heat flow measurements at 30°48.5′N showed that the inner-rift-bounding faults may serve as water recharge zones, but that they are not necessarily areas of focussed hydrothermal outflow, which instead occurs through the thick basin sediments. The rift basin and arc margin sediments are probably dominated by permeable rhyolitic pumice and ash erupted from submarine arc calderas such as Sumisu and South Sumisu volcanoes.

Shackleton, NJ, van Andel TH, Boyle EA, Jansen E, Labeyrie L, Leinen M, McKenzie J, Mayer L, Sundquist E.  1990.  Contributions from the oceanic record to the study of global change on three time scales — Report of working group 1, Interlaken workshop for past global changes. Global and Planetary Change. 2:5-37.   10.1016/0921-8181(90)90030-G   AbstractWebsite
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