ALBERT

Beschreibung: The continental shelf off the northeastern coast of the United States was the first of our offshore coastal areas to be charted in detail by the Coast and Geodetic Survey, starting on Georges Bank in 1930. The techniques responsible for this increased accuracy in offshore waters were first described by Rudé (1938) and have been constantly improved. From these soundings Veatch and Smith (1939) compiled their set of contour charts aided by a grant from the Penrose Bequest of the Geological Society of America. These soundings reopened the submarine canyon problem first commented upon by Dana (1863), which had gradually lapsed into obscurity from insuffcient data. The reader is, of course, well aware of the major controversy, with all its far reaching implications, which has been precipitated since the 1930 surveys of Georges Bank were brought to the attention of geologists by Shepard (1933). As more of the new surveys were completed, data from the field sheets were kindly furnished by the U. S. Coast and Geodetic Survey to the Woods Hole Oceanographic Institution for use in dredging and coring operations. This field work, first reported in 1936, was continued from time to time until 1941 as new soundings became available. Rock dredging and coring has been carried out in every major canyon on the slope from Corsair Canyon at the tip of Georges Bank to Norfolk Canyon off the entrance to the Chesapeake (Fig. I). Numerous cores have also been taken from the areas in between; and while the whole slope from Georges to the Chesapeake has not been covered, it is believed that no significant areas have been missed. In fact, cores from the slope taken during the summers of 1940 and 1941 have yielded results that are corroborative rather than new. In 1938 on a cruise from Hudson Gorge to Norfolk Canyon, cores were taken on the slope in areas which Veatch had considered to be the most important (personal communication). In the following report the tows and cores will be described by areas from Georges Bank southwards, as the same region was revisited in successive years. The various samples, however, will be referred to by number followed by the year in which they were taken. The material is in storage in the Woods Hole Oceanographic Institution and in the Museum of Comparative Zoology at Harvard University. The late Joseph A. Cushman was kind enough to identify the Foraminifera which have been obtained in tows from the canyon walls and in cores, except for those described in Appendix A which is contributed by Fred B Phleger, Jr. Most of the type material is in storage in the Museum of Comparative Zoology, although at the present writing some is in the Cushman Laboratory in Sharon, Massachusetts. I am indebted to Lloyd W. Stephenson for identifying a molluscan fauna from one of the canyons, and to W. C. Mansfield who has reported on another formation. Numerous discussions with Percy E. Raymond have, as usual, proved most helpful, and thanks are also due to Eugenia C. Lambert for performing the mechanical analyses and to Constance French for other laboratory assistance. Phleger (1939, 1942, 1946) has previously published on the Foraminifera from the slope and deep water cores. This material is, at present, at Scripps Institution of Oceanography.

Beschreibung: The Massachusetts Bays Program made bottom pressure and water velocity observations in Massachusetts and Cape Cod Bays during 1990 and 1991. In the Bays, the sea surface elevation appeared to rise and fall in phase with equal amplitudes at each diurnal or semidiurnal tidal frequency. There is some amplification in Boston and Provincetown harbors. The semidiurnal tides (particularly the M2 constituent) dominate. Massachusetts and Cape Cod Bays are part of the Gulf of Maine/Bay of Fundy system which is resonant near the semidiurnal frequency. This resonance amplifies the importance of the semidiurnal tides so that diurnal and higher harmonic tides become negligible. The sea level tides force currents which move with the same frequencies, but whose amplitudes are affected by the bathymetry. The strongest currents exist in the channel between Race Point and Stellwagen Bank where tidal currents exceed 1 knot. Analysis of current records for their tidal signal is complicated by internal tides which contaminate the records. These internal waves at tidal frequency exist on the stratification in the water column, and disappear during winter well-mixed times. At other times they must be considered as a signifcant source of energy for mixing and resuspension of sediments.

Beschreibung: When the U. S. Bureau of Fisheries, in cooperation with the Museum of Comparative Zoology, commenced the oceanographic survey of the Gulf of Maine in the summer of 1912 (Bigelow, 1925-1927), it was in the hope that this might later be extended to the coastal waters thence southward; eventually even as far as the Gulf of Mexico. Cruises carried out in connection with investigations of the biology of the mackerel, by the Fisheries' steamer "Albatross II" from 1927 to 1932, supplemented by those of the research ship "Atlantis" of the Woods Hole Oceanographic Institution, have made it possible to extend the detailed examination of the physical oceanography of the continental shelf as far as the offing of Chesapeake Bay, and to the offing of Cape Hatteras for some of the months. The present account of the temperature of the region will, it is hoped, be followed shortly by corresponding accounts of salinity, of circulation and of the dominant planktonic communities.

Beschreibung: Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution February, 2006

Beschreibung: In this thesis, I present high-resolution stable-isotope and planktonic-fauna records from Bering Sea sediment cores, spanning the time period from 50,000 years ago to the present. During Marine Isotope Stage 3 (MIS3) at 30-20 ky BP (kiloyears before present) in a core from 1467m water depth near Umnak Plateau, there were episodic occurrences of diagenetic carbonate minerals with very low δ13C (-22:4h), high δ18O (6.5h), and high [Mg]/[Ca], which seem associated with sulfate reduction of organic matter and possibly anaerobic oxidation of methane. The episodes lasted less than 1000 years and were spaced about 1000 years apart. During MIS3 at 55-20 ky BP in a core from 2209m water depth on Bowers Ridge, N. pachyderma (s.) and Uvigerina δ18O and δ13C show no coherent variability on millennial time scales. Bering Sea sediments are dysoxic or laminated during the deglaciation. A high sedimentation rate core (200 cm/ky) from 1132m on the Bering Slope is laminated during the Bolling warm phase, Allerod warm phase, and early Holocene, where the ages of lithological transitions agree with the ages of those climate events in Greenland (GISP2) to well within the uncertainty of the age models. The subsurface distribution of radiocarbon was estimated from a compilation of published and unpublished North Pacific benthic-planktonic 14C measurements (475-2700 m water depth). There was no consistent change in 14C profiles between the present and the Last Glacial Maximum, Bolling-Allerod, or the Younger Dryas cold phase. N. pachyderma (s.) δ18O in the Bering Slope core decreases rapidly (in less than 220 y) by 0.7-0.8% at the onset of the Bolling and the end of the Younger Dryas. These isotopic shifts are accompanied by transient decreases in the relative abundance of N. pachyderma (s.), suggesting that the isotopic events are transient warmings and sustained freshenings.

Beschreibung: The work in this thesis was supported by the National Science Foundation award OPP-9912122 to Lloyd Keigwin, the Oak Foundation of Boston, Massachusetts, the Stanley Watson Fellowship, the Paul Fye Fellowship, and the Academic Programs Office at WHOI.

Beschreibung: Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution October, 1977.

Beschreibung: Sediment traps designed to yield quantitative data of particulate fluxes have been deployed and successfully recovered on four moorings in the deep sea. The traps were designed after extensive calibration of different shapes of containers. Further intercalibration of trap design was made in field experiments over a range of current velocities. Experiments with Niskin bottles showed that concentrations of suspended particulate matter obtained with standard filtration methods were low and had to be increased by an average factor of 1.5 to correct for particles settling below the sampling spigot. The trap arrays were designed to sample the particulate fluxes both immediately above and within the nepheloid layer. The data derived from the traps have been used to estimate vertical fluxes of particles including, for the first time, an attempt to distinguish between the flux of material settling from the upper water column (the "primary flux") and material which has been resuspended from some region of the sea floor (resuspension flux). From these data and measurements of the net nepheloid standing crop of particles one can also estimate a residence time for particles resuspended in the nepheloid layer. This residence time appears to be on the order of days to weeks in the bottom 15 m of the water column and weeks to months in the bottom 100 m. Between 80% and 90% of the particles collected in the six traps where particle size was measured were less than 63 μm. The mean size of particles collected in the nepheloid layer was about 20 μm, and above the nepheloid layer the mean was 11 μm. Less than 3% of the organic carbon produced in the photic zone at the trap sites was collected as primary flux 500 m above the sea floor. The primary flux measured at two sites was enough to supply 75% on the upper Rise and 160% on the mid Rise of the organic carbon needed for respiration and for burial in the accumulating sediments. From an intercomparison of the composition of particles falling rapidly (collected in traps), falling slowly or not at all (collected in water bottles), and resting on the sea floor (from a core top), it was determined that elements associated with biogenic matter, such as Ca, Sr, Cu, and I, were carried preferentially by the particles falling rapidly. Once the particles reached the bottom, the concentration of those elements was decreased through decomposition, respiration, or dissolution. Dissolution appears rapid in the vicinity of the sea floor, because despite an abundance of radiolarians, diatoms, and juvenile foraminifera collected in all traps, these forms were rare in core samples. The dynamic nature of thenepheloid layer makes it possible for particles to be resuspended many times before they are finally buried. This enables sediment to be carried long distances from its origin. The recycling of particles near the sea floor may increase dissolution of silicious and carbonate matter.

Beschreibung: Financial aid was provided in the form of a research assistantship from the Office of Naval Research through MIT and WHOI.

Beschreibung: Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September, 1975

Beschreibung: Erosion processes involving fine-grained marine sediments were studied by using an in situ flume to erode undisturbed bottom sediments on the sea floor in Buzzards Bay, a shallow marine embayment off the Massachusetts coast. Tte muddy sea floor in that area is characterized by a deposit-feeding infauna that reworks the sediments. Observations made with the in situ flume suggest that erosion resistance of compacted bottom sediments is up to twice as great as the erosion resistance of biogenically reworked sediments. Estimates of erosional bed shear stress from the in situ flume experiments are similar to estimates made during this study of bed shear stress developed in near-bottom tidal currents. It is inferred that erosion by the in situ flume produces reasonable estimates of bed shear stress necessary to erode undisturbed bottom sediments on the sea floor. Buzzards Bay muds were redeposited in a laboratory flume and eroded after various periods of reworking by the deposit-feeding organisms contained in them. Other Buzzards Bay mud samples were treated to remove organic matter, and the erosion resistance of flat beds of these sediments was also investigated in a laboratory flume. The surface of a biogenically reworked bed after two months was covered with mounds, burrows, trails, and aggregates composed of sediments and organic material. This bed was similar in appearance to many of the beds eroded by the in situ flume. The two month bed eroded at an erosional shear stress similar to the erosional shear stress necessary to erode the in situ Buzzards Bay muds (0.8 dynes/cm2 ) . Beds biogenically reworked for shorter periods had high values of erosional shear stress, up to twice that of the two month bed. The bed shear stress necessary to erode flat beds of Buzzards Bay sediments increased as the concentration of organic matter in the sediments increased. Deposit-feeders were absent in these beds, and the mode of deposition was kept uniform, so the increase of erosion resistance with increase in organic content is considered a reliable indication of sediment behavior, and not an artifact of experimental conditions. During the in situ experiments, lee drifts were created behind resistant roughness elements on the sea floor. A brief study of lee drift formation in the laboratory suggests that the formation of lee drifts from fine-grained sediments can be predicted to take place when the body Reynolds number of the resistant roughness elements is below a critical value.

Beschreibung: The Office of Naval Research supported this research and provided salary support through grants to the Woods Hole Oceanographic Institution and the Massachusetts Institute of Technology.

Beschreibung: Submitted in partial fulfillment of the requirements for the degree of Doctor of Science at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution March, 1980

Beschreibung: The Southern Ocean as defined here is the body of water between the Antarctic Continent and the Antarctic Polar Front, (APF). This ocean is considered important in the global thermodynamic balance of the ocean-atmosphere system because large planetary heat losses are believed to occur at high latitudes. The ocean and atmosphere must transport heat poleward to balance these losses. In the Southern Hemisphere, the oceanic contribution to this flux involves a southward transport of heat across the APF into the Southern Ocean where it is given up to the atmosphere through air-sea interactions. In Part I, the air-sea interactions and structure of the near surface waters of the Southern Ocean are investigated with a three dimensional time dependent numerical model. The surface waters in this region in summer are characterized by a relatively warm surface mixed layer with low salinity. Below this layer, a cold temperature extremum is usually observed in vertical profiles which is believed to be the remnant of a deep surface mixed layer produced in winter. The characteristics of this layer, the surface mixed layer and the observed distribution of wintertime sea ice are reproduced well by this model. Unlike some other sea-ice models the air-sea heat exchange is a free variable. Model estimates of the annual heat loss by the Southern Ocean exhibit the observed meridional variation of heat gained by the ocean along the APF with heat lost further south. The model's area average heat loss is much smaller than that estimated with direct observations. While several model parameterizations were made which could be in error, the model results suggest that the Southern Ocean does give up vast amounts of heat to the atmosphere away from the continental margins. The model results and direct calculations of air-sea exchanges suggest a southward heat flux must occur across the APF. The lateral water mass transition across the front is not discontinuous but occurs over a finite sized zone of fluid which is dominated by intrusive finestructure. The characteristics and dynamics of these features are investigated in Part II to try and assess their importance in the meridional heat budget. Observations made on two cruises to the APF are presented and the space-time scales of the features and thermohaline characteristics are discussed. It is suggested that double diffusive processes dominated by salt fingering are active within the intrusions. An extension of Stern's (1967) model of the stability of a thermohaline front to intrusive finestructure driven by saltfingering where small scale viscous processes are included, is presented to explain why intrusions are observed in frontal zones. The model successfully predicts vertical scales of intrusions observed in the ocean and the observed dependence of the intrusions' slopes across density surfaces on the vertical scale. Since the fastest growing intrusion is not strongly determined by the model, though, it is likely that finite amplitude effects determine the dominant scale of interleaving in the ocean. The analysis predicts that intrusions transport heat, salt and density down the mean gradients of the front. For the APF, this heat flux is poleward which is the direction required by the global heat budget. This model does not describe intrusions at finite amplitude or in steady state and so cannot be used to estimate the magnitude of the poleward heat flux due to intrusions in the APF.

Beschreibung: The research reported on here, and my support as a graduate student was provided by the National Science Foundation through grants OCE 75 14056. OCE 76 82036 and OCE 77 28355.

Beschreibung: Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution August 1982

Beschreibung: In an effort to understand the more general mechanisms and rates of pre-depositional reactions that transform organic matter, the types and relevant time scales of reactions that transform carotenoid pigments in the oceanic water column were studied. Suspended particulate matter collected from surface waters of Buzzards Bay, Massachusetts and the Peru upwelling system has a carotenoid distribution reflecting the phytoplanktonic source of the material. The carotenoid distribution of sediment trap samples collected in these same areas was dominated by transformation products. Fucoxanthin, the primary carotenoid of marine diatoms, typically constituted 77-100% of the total fucopigments in suspended particulate material. In sediment trap samples this pigment constituted only 4-85% of the total. The remaining 15-96% of the pigments consisted of the fucoxanthin transformations products: free alcohols (2-94%), dehydrates (0-6%), and opened epoxides (0-19%). Preliminary results suggest that carotenoid esters are hydrolyzed to free alcohols at a rate determined by the turnover of primary productivity. The dehydrated and epoxide opened intermediates of fucoxanthin represent products of transformation reactions that operate over much longer time scales (0.1-10 yrs). Dehydration and epoxide opening are not significant water column transformations, but are important in surface sediments.

Beschreibung: This research was supported by the Ocean Sciences Section, National Science Foundation grants OCE 79-25352 and OCE 81-18436, the Office of Naval Research Contract N00014-74-Co-262NR 083-004, the Woods Hole Coastal Research Center project 25 000067 04, and a Woods Hole Oceanographic Institution Student Fellowship.

Beschreibung: Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution May 1980

Beschreibung: This study of particulate matter in the water column and the underlying surface sediments verifies the occurrence of local, present-day resuspension in the deep sea. The location of the major portion of this work was the South Iceland Rise, a region influenced by the flow of Norwegian Sea Overflow Water. Measured current velocities exceeded 20 cm/sec in the axis of the bottom current for the duration of the deployments, approximately two weeks. Particulate matter was sampled with Niskin bottles, to obtain the standing crop of suspended matter and with sediment traps, to obtain the material in flux through the water column. Box cores were taken to obtain surface sediment samples for comparison with the trap samples. Suspended particulate matter (SPM) and light-scattering studies demonstrate that in the Iceland Rise area the correlation of the L-DGO nephelometer to concentration of SPM differs between clear water and the nepheloid layer. Correlations of light scattering to SPM concentration also differ regionally, but for predicting concentration from light scattering, regression lines at two locations are indistinguishable. Particle size distributions have lower variance in the nepheloid layer than those in clear water which have roughly equal volumes of material in logarithmically increasing size grades from 1-20 μm. Apparent density differences between SPM in clear water and the nepheloid layer are not distinguishable in the Iceland Rise study; apparent densities increase in the nepheloid layer in the western North Atlantic. An apparent density of 1.1 g/cm3 adequately separates clear water from nepheloid layer samples in this region. Compositional variations seen between clear water and the nepheloid layer include a decrease in small coccoliths and an increase in clays and mineral matter. These compositional variations are more dramatic in the western North Atlantic region, due to dissolution of carbonate at the seafloor, later resuspended into the nepheloid layer. Sedimentological evidence of resuspension and redistribution of material are: 1) presence of sediment drifts throughout the Iceland Basin; 2) occurrence of coarse, glacial age sediments beneath the axis of the bottom current; and 3) differences in mineralogy, carbonate and organic carbon contents between surface sediments beneath the bottom current and those in a channel. A comparison of the vertical flux of material measured by sediment traps at 500 meters above bottom (mab) with the accumulation rate in cores, shows that the present-day surface input is an order of magnitude smaller than the accumulation rate. This observation suggests transport of material into some sections of the region by bottom currents or by turbidity currents. The horizontal flux of particulate matter into and out of the region by the bottom current is 100 kg/sec. This material may contribute to the formation of Gardar sediment drift downstream. The trends in % CaC03 and % organic carbon through the water column and in the surface sediments suggest that dissolution of carbonate and decomposition and consumption of organic carbon occurs primarily at the seafloor. These data also suggest preferential preservation at channel stations and/or preferential erosion beneath the bottom current. A comparison of sediment-trap samples with box-core surface samples further supports present-day resuspension. Benthic foraminifera, iron-oxidicoated planktonic foraminifera and the glacial, subpolar planktonic foraminifera (Neogloboquadrina pachyderma (sinistral)) in traps at 10,100 and a few specimens at 500 mab, provide conclusive evidence for local resuspension. The coarse fraction (〉125 μm) of the sediment trap material collected at 10 mab comprises 21-34% of the samples Calculations indicate that this material is locally derived (few kilometers) resuspended material.

Beschreibung: This work was financially supported by the Woods Hole Oceanographic Institution, ONR through contracts N00014-79-C-00-7l NR 083-004, N00014-74-C0262 NR 083-004, and N00014-75-C-029l and ERDA through contracts 13-7923 and 13-2559.

Beschreibung: Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September 2003

Beschreibung: The cosmogenic radionuclide 10Be is a unique tracer of shallow sediment subduction in volcanic arcs. The range in 10Be enrichment in the Central American Volcanic Arc between Guatemala and Costa Rica is not controlled by variations in 10Be concentrations in subducting sediment seaward of the Middle America Trench. Sedimentary 10Be is correlated negatively with 143Nd/144Nd, illustrating that 10Be concentrations varied both between and within cores due to mixing between terrigenous clay and volcanic ash endmember components. This mixing behavior was determined to be a function of grain size controls on 10Be concentrations. A negative correlation of bulk sedimentary 10Be concentrations with median grain size and a positive correlation with the proportion of the sediment grains that were 〈32 μm in diameter demonstrated that high concentrations of 10Be in fine-grained, terrigenous sediments were diluted by larger grained volcanogenic material. The sharp decrease in 10Be enrichment in the Central American Volcanic Arc between southeastern Nicaragua and northwestern Costa Rica correlates with changes in fault structure in the subducting Cocos plate. Offshore of Nicaragua, extensional faults associated with plate bending have throw equal to or greater than the overlying subducting sediment thickness. These faults enable efficient subduction of the entire sediment package by preventing relocation of the décollement within the downgoing sediments. Offshore of Costa Rica, the reduction of fault relief results in basement faults that do not penetrate the overlying sediment. A conceptual model is proposed in which the absence of significant basement roughness allows the décollement to descend into the subducting sediment column, leading to subsequent underplating and therefore removal of the bulk of the sediment layer that contains 10Be. Basement fault relief was linearly related to plate curvature and trench depth. The systematic shoaling of the plate from southeastern Nicaragua to northwestern Costa Rica is not explained by changes in plate age for this region. Instead, it is hypothesized that the flexural shape of the plate offshore of southeastern Nicaragua and northwestern Costa Rica represents a lateral response to a buoyant load caused by the thick crust and elevated thermal regime in the Cocos plate offshore of southeastern Costa Rica.

Beschreibung: Funding for this work was provided by the National Science Foundation Graduate Research Fellowship, the WHOI Ocean Ventures Fund, the WHOI Deep Ocean Institute Graduate Fellowship, and Geological Society of America Graduate Research Grant #7179-02.