Oceanography

Ocean Salinities Reveal Strong Global Water Cycle Intensification during 1950-2000

by Paul J. Durack

Science, 2012

Fundamental thermodynamics and climate models suggest that dry regions will become drier and wet regions will become... more Fundamental thermodynamics and climate models suggest that dry regions will become drier and wet regions will become wetter in response to warming. Efforts to detect this long-term response in sparse surface observations of rainfall and evaporation remain ambiguous. We show that ocean salinity patterns express an identifiable fingerprint of an intensifying water cycle. Our 50-year observed global surface salinity changes, combined with changes from global climate models, present robust evidence of an intensified global water cycle at a rate of 8 ± 5% per degree of surface warming. This rate is double the response projected by current-generation climate models and suggests that a substantial (16 to 24%) intensification of the global water cycle will occur in a future 2° to 3° warmer world.

A method to evaluate metal enrichment in marine sediments

by Eric Alfaro

Lizano, O., E. Alfaro y A. Salazar, 2012. Un método para evaluar el enriquecimiento de metales en sedimentos marinos en Costa Rica. Rev. Biol. Trop. 60(Supl. 2). 197-211.

Abstract: In order to evaluate metal enrich-
ment in sediments , a method is proposed and tested in Bahia Culebra... more Abstract: In order to evaluate metal enrich-
ment in sediments , a method is proposed and tested in Bahia Culebra and the Golfo de Nicoya, Costa Rica
through the normalization of the elements against aluminum, and by linear regression of the logarithm of the
concentrations of different elements respect to aluminum. The distributions of the elements manganese, and
strontium of Bahía Culebra did not satisfy the tests of normalization and linear regression, indicating a non-
natural distribution or enrichment of these elements in this region. In the Golfo de Nicoya the elements copper
, zinc , rubidium and the strontium did not satisfy the test of normality or the linear regression with respect
to aluminum, indicating a possible enrichment of these elements. The majority of the concentrations of the ele-
ments in two sample sites, with the exception of chromium, are within the natural ranges in rocks or clays of
marine sediments, and within the concentration ranges of other studies done in these same regions. Chromium
has average values beyond the natural concentrations, the values of some samples in the Golfo de Nicoya are up
to 10 times greater than the concentration value of a typical bay with high contamination of this element. Rev.
Biol. Trop. 60 (Suppl. 2): 197-211.

On nitrogen fixation and preferential remineralization of phosphorus

by Fanny Monteiro

Co-authored with Fanny Monteiro and Mick Follows, published in 'Geophysical Research Letters', 2012

Regional and global nitrogen fixation rates are often estimated from geochemical tracers related to N* (= NO3 −... more Regional and global nitrogen fixation rates are often estimated from geochemical tracers related to N* (= NO3 − 16PO4). However the patterns of this tracer reflect the influence of numerous processes including nitrogen fixation, denitrification, remineralization of organic matter, variable stoichiometry, atmospheric deposition and physical transport. Here we have used idealized models to illustrate how preferential remineralization of organic phosphorous may explain observed features of N* distribution in the North Atlantic Ocean, including a subsurface maximum and an increased temporal variability in the mid-thermocline. If preferential remineralization of phosphorus is key in shaping the oceanic distribution of N*, published estimates of nitrogen fixation may be underestimating the marine nitrogen fixation rate by as much as a factor of three.

Coastal Systems - Korean translation

by Simon Haslett

My Coastal Systems textbook is now available in Korean.

Wind-Waves in the Coupled Climate System

by Baylor Fox-Kemper

L. Cavaleri, B. Fox-Kemper, and M. Hemer. Wind waves in the coupled climate system. Bulletin of the American Meteorological Society, 2012. In press.

We stress the role waves play in modulating interactions between oceans and atmosphere. All exchanges (e.g., momentum,... more We stress the role waves play in modulating interactions between oceans and atmosphere. All exchanges (e.g., momentum, energy, heat, mass, radiation fluxes) are influenced by the geometrical and physical characteristics of the ocean surface, which separates the atmospheric and oceanic boundary layers. We provide a qualitative overview of the main relevant surface gravity wave driven processes at the air-sea interface which may have an important role on the coupled climate system in general and the atmospheric and oceanic boundary layers in particular.

Capsule summary

Wind waves do regulate the exchanges between the atmosphere and the ocean. Here we outline and describe the main processes at work.

The form and orientation of Langmuir cells for misaligned winds and waves

by Baylor Fox-Kemper

L. Van Roekel, B. Fox-Kemper, P. P. Sullivan, P. E. Hamlington, and S. R. Haney. The form and orientation of Langmuir cells for misaligned winds and waves. Journal of Geophysical Research-Oceans, 117:C05001, 22pp, 2012.

Large eddy simulations of the Craik-Leibovich equations are used to assess the effect of misaligned Stokes drift and... more Large eddy simulations of the Craik-Leibovich equations are used to assess the effect of misaligned Stokes drift and wind direction on Langmuir cells in the ocean mixed layer. Misalignments from 0{degree} to 135{degree} are examined and Langmuir turbulence structures are evident in all cases. The Stokes drift is modeled using a broadband empirical spectrum, and cases with and without the Coriolis effect, wind waves, and an initial mixed layer are examined. The expected scaling for the vertical velocity variance is recovered in the aligned simulations and is adapted here to the misaligned cases. The adjusted scaling projects the friction velocity (aligned with the wind stress) into the dominant axial direction of the Langmuir cells. The turbulent Langmuir number is generalized through a similar projection into the axial direction of the Langmuir cells, which reduces its value in realistic conditions. For known Langmuir cell orientations, the strength of Langmuir turbulence for misaligned cases can be estimated using the projected Langmuir number. A prediction for the angle between the wind stress and cell direction is obtained using the law of the wall; this prediction only requires the wind stress, Stokes drift, and boundary layer depth. Conditional analyses show that, with increasing misalignment, the typically antisymmetric Langmuir cell pairs become asymmetric. This asymmetry is due, in part, to the advection by cross cell flow of vorticity from one vortex tube onto the other, and in part due to an asymmetry induced by the stretching of vertical vorticity into cross cell vorticity.

Mythos Atlantis - Historia Pangaea

by Sean Bambrough

rough draft only

after investigation we arrived at thesis of which the main points are: Atlantis was a real continent, was in the... more after investigation we arrived at thesis of which the main points are: Atlantis was a real continent, was in the Atlantic but is not the Atlantic, Atlantis didn't sink it shifted, Atlantis was all or part of south &/or north America/s, (ca 1400 bc not 9000 bc,) ancient American (and Polynesian) origins. the paper give our evidences for these and other points (22 in all).

Upper Cretaceous inter-hemispheric correlation between the Southern Tethys and the Boreal: chemo-and biostratigraphy and paleoclimatic reconstructions from a new section in the Tethys Himalaya, S-Tibet

by Ines Wendler

Wendler, I., Willems, H., Gäfe, K.-U., Ding, L., Luo, H., 2011. Newsletters on Stratigraphy, 44 (2), 137-171.

A new, 430 m long and mostly continuous Upper Cretaceous section from southern hemisphere low paleolatitudes in the... more A new, 430 m long and mostly continuous Upper Cretaceous section from southern hemisphere low paleolatitudes in the Tethys Himalaya (Guru, Tibet) is presented. The lithology, microfacies and fossil contents of the Guru section indicate a continuous shallowing trend from open oceanic conditions at the slope during the Turonian to shallow marine inner shelf environments in the Maastrichtian, interrupted by short periods of stagnation or slight deepening. Strong variations in sedimentation rates and contents of carbonate, quartz, organic carbon and sulfur appear to reflect a combination of regional and global processes. On regional scale, the patterns of varying clastic sediment supply seem to be related to the fast northward drift of the Indian plate from the temperate climate belt in the Turonian and Coniacian, crossing the arid zone during the Santonian and early Campanian, and passing into the tropical humid belt in the late Campanian. On global scale, similar sedimentary changes as in Guru with a transition from clay-rich Turonian sediments to Coniacian carbonates are found in other regions of the world, suggesting an additional influence of global oceanic and climatic factors. Intervals of omission, erosion and reworking in upper Coniacian and lower Campanian sediments of the Guru section appear to coincide with global sea-level lowstands.
Well preserved planktic foraminifera occur over most of the Guru section and provide good biostratigraphic control for correlation of stable carbon and oxygen isotopes with data from the reference section for the boreal white chalk in northern Germany at Lägerdorf-Kronsmoor and with the English Chalk reference section, showing detailed correlation of bulk sediment carbon isotopes and comparable trends in oxygen isotopes. The Campanian and Maastrichtian carbon isotope fluctuations can be related to cyclic variations in carbonate content at Lägerdorf-Kronsmoor which are thought to be driven by long eccentricity. This indicates orbital forcing of both carbonate accumulation and carbon isotope signature, most likely mediated by global sealevel changes. The possibility of detailed d13C correlation from boreal sections of the northern hemisphere to a low-latitude section of the southern hemisphere allows for global correlation with an accuracy not achieved by biostratigraphic methods so far. It further enables linking of microfossil and macrofossil biozones, facilitating precise comparison of shallow and deep water sections, which is essential for the improvement of our understanding of timing, causes and effects of climatic and oceanographic processes.

Productivity fluctuations and orbital cyclicity during onset of Early to Middle Turonian marine red-bed formation (Austrian Eastern Alps)

by Ines Wendler

Wendler, I., Wendler, J.E., Neuhuber, S., Wagreich, M., 2009. Cretaceous Oceanic Red Beds: Stratigraphy, Composition, Origins, and Paleoceanographic and Paleoclimatic Significance, SEPM Special Publication, 91, 209-221.

A section from the Ultrahelvetic units of Upper Austria comprises the transition from light-gray, upper-bathyal to... more A section from the Ultrahelvetic units of Upper Austria comprises the transition from light-gray, upper-bathyal to middlebathyal carbonates of Early Turonian age towards red-colored carbonates of the Middle Turonian. The total-organic-carbon content is very low throughout the section, but benthic foraminifera associations, especially high abundance of Tappanina laciniosa, indicate repeated phases of enhanced organic-matter flux and decreased oxygen concentrations at the seafloor. The overlying reddish layers are enriched in iron oxides and hydroxides and pyrite and may represent paleo–redox fronts that were related to periods of well oxygenated bottom waters, reduced sedimentation rates, and degradation of organic matter in the underlying sediments. Cyclic sedimentary packages consist of four marlstone–limestone couplets with upward-increasing bedding thickness, red carbonates at the base, and a gray limestone bed at the top. Based on carbon isotope stratigraphy, these packages reflect the 400 kyr eccentricity cycle, with the four marlstone–limestone couplets representing the 100 kyr cycle. Three 400-kyr-cycle boundaries are preceded by horizons with high T. laciniosa abundance and are followed by a paleo-redox front and red-bed deposition. Thus, there is indication of the temporary presence of a local oxygen-minimum zone during enhanced production at the end of each 400 kyr cycle, possibly linked to sea-level fluctuations. Organic-carbon fluxes seem to have decreased immediately above the cycle boundaries. Recycling of organic carbon could be responsible for the distinct carbon-isotope minima at the base of each cycle. Accumulation rates based on our orbital model suggest a switch from relatively uniform sedimentation rates in the Early Turonian to cyclic fluctuations of sedimentation rates in the Middle Turonian. The occurrence of three 400 kyr cycles between the main carbon-isotope excursions points to a 1.2 Myr periodicity, which may reflect the Earth’s long obliquity cycle. A long-term
increase in bottom-water aeration from the Early to the Middle Turonian is evident from the increasing dominance of red sediments.

Early Turonian shallow marine red beds on the Levant carbonate platform (Jordan), Southern Tethys

by Ines Wendler

Wendler, J., Wendler, I., Kuss, J., 2009. Cretaceous Oceanic Red Beds: Stratigraphy, Origins, Paleoceanographic and Paleoclimatic Significance, SEPM Special Publication, 91, 171-179.

A one-meter-thick marine red bed (Cretaceous oceanic red beds, CORBs) is reported from Early Turonian sediments... more A one-meter-thick marine red bed (Cretaceous oceanic red beds, CORBs) is reported from Early Turonian sediments associated with the Levant carbonate platform in central Jordan. These CORBs are of regional significance, in that deposits similar in facies and age are present in various sections of the Levant carbonate platform farther southwest in the Sinai. The red bed represents a rare shallow marine counterpart to the widely known deeper marine CORBs. The onset of sedimentation of these brick-red marls in a shallow sea (shallow subtidal) of the southern Tethys margin is shown to be synchronous with the Tethys-wide onset of marine red beds in oceanic settings in the latest Early Turonian. The transition into red marls marks a significant change in sedimentation from marly, gypsum-rich clay, representing lowstand deposits below, into a sequence including massive platform limestone beds forming a transgressive systems tract above the red bed. The sedimentary conditions on the Levant platform during red-bed deposition show some similarities to its deeper marine counterparts on the Northern Tethys margin: they are related to strongly fluctuating sedimentation rates, and they follow periods of high marine productivity, which occurred in the aftermath of AE2. It is obvious that both strong synsedimentary fluctuations in water depth and accumulation rate and significant early and late evaporite diagenesis influenced the investigated section, so the cause of the red coloring is likely to be not solely a synsedimentary feature. The time-equivalent onset of shallow marine red beds and deep marine red beds
in the Early Turonian indicates that both share common global prerequisites regardless of the paleobathymetry.

Oxygen availability effects on early diagenetic calcite dissolution in the Arabian Sea as inferred from calcareous dinoflagellate cysts

by Ines Wendler

Wendler, I., Zonneveld, K.A.F., Willems, H., 2002. Global and Planetary Change, 34, 219-239.

In oceanic regions with high primary production, such as the Arabian Sea, the primary signals of proxies are often... more In oceanic regions with high primary production, such as the Arabian Sea, the primary signals of proxies are often altered by diagenetic processes. The present study aims at assessing the effects of early diagenesis on calcareous dinoflagellate cysts, which represent a relatively new tool for reconstructing the paleoenvironmental conditions within the photic zone. For this purpose, surface sediment samples from within and below the oxygen minimum zone (OMZ) of the northeastern and southwestern Arabian Sea have been analysed quantitatively for their calcareous dinoflagellate cyst content. The calculated cyst accumulation rates (ARs), the relative abundances and cyst fragmentation values were compared to bottom water oxygen (BWO) content and ARs of organic carbon at the sample positions. Different patterns were found in the northeastern and southwestern part of the Arabian Sea. In the SW, no relationship between cyst ARs and BWO is distinguishable, and the distribution of cyst ARs is thought to largely reflect primary cyst production. In the NE, much higher ARs of all species are found in samples from within the OMZ in comparison to samples from below it. This is interpreted to result from better calcite preservation within the OMZ, presumably due to reduced oxic degradation of organic matter. The differential drop of cyst ARs of the individual species at the lower boundary of the OMZ in the NE Arabian Sea, as well as the species-specific change in relative abundance and fragmentation, indicate different sensitivity to calcite dissolution of the different species. These results show that early diagenetic calcite dissolution can change both relative and absolute abundances of calcareous dinoflagellate cysts, which has to be considered if using them for paleoenvironmental reconstructions. Furthermore, it is shown that considerable calcite dissolution can occur above the carbonate saturation horizon in high productive areas. However, calcite preservation can be substantially increased, as soon as oxygen concentrations are too low for oxic degradation of OM. Under low oxic conditions (within and near the OMZ), the main factor controlling organic matter (OM) preservation appears to be BWO concentrations. Under higher oxygen levels (below f1500 m depth in the NE Arabian Sea) there seems to be an increasing influence of bioturbation and sedimentation rate on the preservation of OM by controlling its oxygen exposure time. This study presents an example of a highly productive basin in which differences in early diagenetic processes can lead to the preservation of a signal that is either dominated by primary production (off Somalia) or by secondary alteration (off Pakistan), although in both areas, an oxygen depleted zone is present. For estimating the effects of early diagenetic calcite dissolution in a sediment by metabolic CO2 (and
probably by H2S oxidation), not only the content of organic carbon but also other geochemical proxies for paleoredoxconditions
have to be included for paleoenvironmental reconstructions.

Production of calcareous dinoflagellate cysts in response to monsoon forcing off Somalia: a sediment trap study

by Ines Wendler

Wendler, I., Zonneveld, K.A.F, Willems, H., 2002. Marine Micropaleontology 46, 1-11

To study the ecology of calcareous dinoflagellates we examined the impact of the SW and NE monsoons on cyst formation... more To study the ecology of calcareous dinoflagellates we examined the impact of the SW and NE monsoons on cyst formation using sediment trap material, collected at 1032 m water depth, off Somalia from June 1992 to February 1993. The results do not confirm the relationship between cyst production and lower nutrient concentrations, as highest cyst fluxes were recorded during late SW monsoon under the relatively nutrient-rich and less agitated conditions of mature upwelled water. Lowest cyst fluxes were found under strongly stratified, nutrient-depleted surface waters during the inter-monsoon. Although all of the studied species seem to prefer a stratified water column, an elevated concentration of nutrients appears to be necessary to maintain high cyst production. Comparison of the mean cyst flux to the sediment trap with that into the underlying surface sediments reveals a loss of 81-96%, which can be attributed to calcite dissolution. The relatively small spheres of Thoracosphaera heimii are affected more than the cysts of the other species.

Calcareous cyst-producing dinoflagellates: ecology and aspects of cyst preservation in a highly productive oceanic region

by Ines Wendler

Wendler, I., Zonneveld, K.A.F., Willems, H., 2002. Geological Society, London, Special Publications, 195, 317-340.

Absolute and relative abundances of calcareous dinoflagellate cyst species in surface sediment samples from the... more Absolute and relative abundances of calcareous dinoflagellate cyst species in surface sediment samples from the Arabian Sea are compared with environmental parameters of the upper 100 m of the water column to gain information on their largely unknown autecology. Ten species or morphotypes were encountered of which four occurred only as accessories. On the basis of the distribution patterns of the six more abundant species or morphotypes, the studied area is subdivided into three provinces, demonstrating a clear relationship to monsooncontrolled upper-ocean conditions. The two dominant species, Thoracosphaera heimii and Orthopithonella granifera, show opposite trends in distribution of both their absolute and relative abundances. In the NE Arabian Sea, low absolute and relative abundances of 7: heimii are mainly attributed to enhanced dissolution of the small tests in this region, whereas elevated concentrations of 0. granifera seem to be related to higher water temperatures and the influence of the Indus River. Sphaerodinella albatrosiana and Calciodinellum operosum are most abundant in the open ocean, associated with lower nutrient levels, relatively high temperatures and low seasonality. Spiny cysts (mainly represented by Scrippsiella trochoidea), in contrast, exhibit a more shelf-ward distribution and are most abundant in regions that are influenced by coastal upwelling, characterized by eutrophic and rather unstable conditions with seasonally lower temperatures and a shallow thermocline. A generally negative correlation of calcareous dinoflagellate cysts with primary productivity or high nutrient concentrations, as proposed by other workers, cannot be confirmed. Cyst accumulation rates off Somalia show that strong turbulence and high current speeds are unfavourable for calcareous noflagellates, suggesting
that these organisms are more successfbl under rather stratified conditions.

Torres et al., 2003

by Rodrigo Torres

torres et al., 2011a

by Rodrigo Torres

Molybdenum isotope records as a potential new proxy for paleoceanography

by Chris Siebert

Phanerozoic environments of black shale deposition and the Wilson Cycle

by João Trabucho-Alexandre

Published in 'Solid Earth', 2012.

The spatial and temporal distribution of black shales is related to the development of environments in which they... more The spatial and temporal distribution of black shales is related to the development of environments in which they accumulate and to a propitious combination of environmental variables. In recent years, much has been done to improve our understanding of the mechanisms behind the temporal distribution of black shales in the Phanerozoic and of the environmental variables that result in their deposition. However, the interpretation of ancient black shale depositional environments is dominated by an oversimplistic set of three depositional models that do not capture their complexity and dynamics. These three models, the restricted circulation, the (open) ocean oxygen minimum and the continental shelf models, are an oversimplification of the variety of black shale depositional environments that arise and coexist throughout the course of a basin's Wilson Cycle, i.e. the dynamic sequence of events and stages that characterise the evolution of an ocean basin, from the opening continental rift to the closing orogeny. We examine the spatial distribution of black shales in the context of the Wilson Cycle using examples from the Phanerozoic. It is shown that the geographical distribution of environments of black shale deposition and the position of black shales in the basin infill sequence strongly depend on basin evolution, which controls the development of sedimentary environments where black shales may be deposited. The nature of the black shales that are deposited, i.e. lithology and type of organic matter, also depends on basin evolution and palaeogeography. We propose that in studies of black shales more attention should be given to the sedimentary processes that have led to their formation and to the interpretation of their sedimentary environments.

The distribution of dissolved iron and aluminum in the Beaufort Sea

by Jay Cullen

The biogeochemistry of cadmium and iron in the ocean: Uptake by marine phytoplankton

by Jay Cullen

Silver in the subarctic northeast Pacific Ocean: Explaining the basin scale distribution of silver

by Jay Cullen