Global Ocean Particulate Organic Carbon flux merged with satellite parameters

The efficiency of the biological pump of carbon to the deep ocean depends largely on the biologically mediated export of carbon from the surface ocean and its remineralization with depth. Global satellite studies have primarily focused on chlorophyll concentration and net primary production (NPP) to understand the role of phytoplankton in these processes. Recent satellite retrievals of phytoplankton composition now allow for the size of phytoplankton cells to be considered. Here, we improve understanding of phytoplankton size structure impacts on particle export, remineralization and transfer. Particulate organic carbon (POC) flux observations from sediment traps and 234Th are compiled across the global ocean. Annual climatologies of NPP, percent microplankton, and POC flux at four time series locations and within biogeochemical provinces are constructed, and sinking velocities are calculated to align surface variables with POC flux at depth. Parameters that characterize POC flux vs. depth (export flux ratio, labile fraction, remineralization length scale) are then fit to the aligned dataset. Times of the year dominated by different size compositions are identified and fit separately in regions of the ocean where phytoplankton cell size showed enough dynamic range over the annual cycle. Considering all data together, our findings support the paradigm of high export flux but low transfer efficiency in more productive regions and vice versa for oligotrophic regions. However, when parsing by dominant size class, we find periods dominated by small cells to have both greater export flux and lower transfer efficiency than periods when large cells comprise a greater proportion of the phytoplankton community.

Compression and expansion index and void ratio of samples from Lomonosov Ridge and Yermak Plateau

With the coupled use of multibeam swath bathymetry, high-resolution subbottom profiling and sediment coring from icebreakers in the Arctic Ocean, there is a growing awareness of the prevalence of Quaternary ice-grounding events on many of the topographic highs found in present water depths of <1000 m. In some regions, such as the Lomonosov Ridge and Yermak Plateau, overconsolidated sediments sampled through either drilling or coring are found beneath seismically imaged unconformities of glacigenic origin. However, there exists no comprehensive analysis of the geotechnical properties of these sediments, or how their inferred stress state may be related to different glacigenic processes or types of ice-loading. Here we combine geophysical, stratigraphic and geotechnical measurements from the Lomonosov Ridge and Yermak Plateau and discuss the glacial geological implications of overconsolidated sediments. The degree of overconsolidation, determined from measurements of porosity and shear strength, is shown to result from consolidation and/or deformation below grounded ice and, with the exception of a single region on the Lomonosov Ridge, cannot be explained by erosion of overlying sediments. We demonstrate that the amount and depth of porosity loss associated with a middle Quaternary (~ 790-950 thousand years ago - ka) grounding on the Yermak Plateau is compatible with sediment consolidation under an ice sheet or ice rise. Conversely, geotechnical properties of sediments from beneath late Quaternary ice-groundings in both regions, independently dated to Marine Isotope Stage (MIS) 6, indicate a more transient event commensurate with a passing tabular iceberg calved from an ice shelf.

Quaternary through early Eocene benthic foraminifera off Peru

Stratigraphic assemblages of Quaternary through early Eocene benthic foraminifers were recovered among 10 Peru margin drill sites. Various hiatuses and intervals barren in foraminifers characterize the sections, but numerous samples contain abundant, well-preserved benthic foraminifers. Bathymetry of the extant species and California-based estimates of the paleobathymetry of the extinct species permit recognition of Quaternary sea-level fluctuations between shelf and upper bathyal depths that produced vertical migrations of oxygenated and low-oxygen habitats at the six shallow sites. Assemblages from lower-slope sites at about 9° and 11°S indicate a general subsidence of the continental margin from shelf or upper bathyal depths in Eocene time to the present lower bathyal depths. Data from 11°S suggest a major part of this subsidence occurred in late Oligocene to early Miocene time. Downslope-transported shelf specimens, particularly the small biserial species, Bolivina costata and B. vaughani, are major contributors to these lower bathyal assemblages from the middle Miocene through Quaternary time.

Eruption of the Håkon Mosby mud volcano recorded by the long-term observatory on mud-volcano eruptions (LOOME) between 2009 and 2010

Submarine mud volcanoes are considered an important source of methane to the water column. However, the temporal variability of their fluid transport including mud and methane emissions is largely unknown. Assuming that this transport was continuous and at steady state, methane emissions were previously proposed to result from a dynamic equilibrium between upward migration and consumption at the seabed by methane-consuming microbes. Here we have investigated non-steady state situations of vigorous mud movements and their reflection in fluid flow, seabed temperature and bathymetry. Time series of pressure, temperature, pH and seafloor photography were collected by a benthic observatory (LOOME) for 431 days at the active Håkon Mosby mud volcano. These new data document eruptions, which were accompanied by pulses of hot subsurface fluids and triggered rapid sediment uplift and lateral movement, as well as emissions of free gas.

Stable isotopic record of late Pliocene and Pleistocene foraminifera of ODP Site 114-704

We studied the stable isotopic and carbonate stratigraphy of ODP Hole 704A to reconstruct the paleoceanographic evolution of the eastern subantarctic sector of the South Atlantic Ocean. Site 704 is well positioned with respect to latitude (46°52.8'S, 7°25.3'E) and bathymetry (2532 m) to monitor past migrations in the position of Polar Front Zone (PFZ) and changes in deep-water circulation during the late Pliocene-Pleistocene. Several important changes occurred in proxy paleoceanographic indicators across the Gauss/Matuyama boundary at 2.47 Ma: (1) accumulation rates of biogenic sedimentary components increased by an order of magnitude (Froelich et al., this volume); (2) planktonic d1 8O values increased by an average of 0.5 per mil; (3) the amplitude of the benthic d18O signal increased; (4) the accumulation rate of ice-rafted detritus increased several fold (Warnke and Allen, this volume); and (5) carbon isotopic ratios of benthic foraminifers decreased by 0.5 per mil, as did the d13C of the fine-fraction carbonate by 1.5 per mil (Mead et al., 1991, doi:10.2973/odp.proc.sr.114.152.1991), but no change occurred in planktonic foraminiferal d13C values. Most of these changes are consistent with more frequent expansions and contractions of the PFZ over Site 704 after 2.47 Ma, bringing cold, nutrient-rich waters to 47°S that stimulated both carbonate and siliceous productivity. The synchronous increase in d18O values and ice-rafted detritus accumulation in Hole 704A indicates that the 2.4 Ma paleoceanographic event included ice volume growth on both Antarctica and Northern Hemisphere continents. The decrease in benthic d13C values indicates that the ventilation rate of Southern Ocean deep water decreased and the nutrient content increased during glacial events after 2.5 Ma. At the Gauss/Matuyama boundary, benthic d13C values of the Southern Ocean shifted toward those of the Pacific end member, indicating a decrease in the relative mixing ratio of Northern Component Water and Circumpolar Deep Water. During the early Matuyama (~2.3 to 1.7 Ma), the PFZ generally occupied a southerly position with respect to Site 704 and carbonate productivity prevailed. Exceptions to these general conditions occurred during strong glacial events of the early Matuyama (e.g., isotopic stages 82, 78, 74, and 70), when the PFZ migrated to the north and opal sedimentation predominated at Site 704. At 1.7 Ma, the PFZ migrated toward the equator and occupied a more northerly position for a prolonged interval between ~1.7 and 1.5 Ma. Beginning at ~1.5-1.4 Ma, surface and bottom water parameters (d18O, d13C, %CaCO3, and %opal) in the subantarctic South Atlantic became highly correlated such that glacial events (d18O maxima) corresponded to d13C and carbonate minima and opal maxima. This pattern is typical of the correlation found during the latest Pleistocene in the Southern Ocean (Charles and Fairbanks, in press). This event coincided with increased suppression of Northern Component Water during glacial events after 1.5 Ma (Raymo et al., 1990, doi:10.1016/0012-821X(90)90051-X), which may have influenced the climatology of the Southern Hemisphere by altering the flux of heat and salt to the Southern Ocean).

Terrain model of the Håkon Mosby Mud Volcano (10 m grid size)

The Håkon Mosby Mud Volcano is a natural laboratory to study geological, geochemical, and ecological processes related to deep-water mud volcanism. High resolution bathymetry of the Håkon Mosby Mud Volcano was recorded during RV Polarstern expedition ARK-XIX/3 utilizing the multibeam system Hydrosweep DS-2. Dense spacing of the survey lines and slow ship speed (5 knots) provided necessary point density to generate a regular 10 m grid. Generalization was applied to preserve and represent morphological structures appropriately. Contour lines were derived showing detailed topography at the centre of the Håkon Mosby Mud Volcano and generalized contours in the vicinity. We provide a brief introduction to the Håkon Mosby Mud Volcano area and describe in detail data recording and processing methods, as well as the morphology of the area. Accuracy assessment was made to evaluate the reliability of a 10 m resolution terrain model. Multibeam sidescan data were recorded along with depth measurements and show reflectivity variations from light grey values at the centre of the Håkon Mosby Mud Volcano to dark grey values (less reflective) at the surrounding moat.

Physiography of the Orca Seamount in the Bransfield Strait, Antarctic Peninsula

Extract from related chapter 5.5.2 in reference: The Orca Seamount was discovered in the central basin of the Bransfield Strait around the posit 62°26'S and 58°24'W on the west side of the Antarctic Peninsula, the most western area of the south polar continent. Through the discovery was made known in 1987, it was only during three bathymetric surveys with high resolution fan echosounders between 1993 and 1995 that the character and complete shape of a remarkable volcano seamount became evident. The data acquisition and processing revealed a spectacular crater of 350 m depth. The relative hight of this 3 km wide "caldera" rim is 550 m with a basal diameter of the seamount cone of 11 km. Its flanks are about 15° steep but in some places the slope reaches up to 36°. The nearly circular shape of the Orca edifice spreads outh with several pronounced spurs, trending parallel to the basin axis in a northeast-southwest direction. The Bransfield Strait is a trough-shaped basin of 400 km length and 2 km depth between the South Shetland Island Arc and the Antarctic Peninsula, formed by rifting behind the islands. The separation of the South Shetland island chain from the peninsula began possibly several million years ago. The active rifting is still going on however, and has caused recent earthquakes and volcanism along the Bransfield Strait. The Strait hosts a chain of submerged seamounts of volcanic origin with the presently inactive Ora Seamount as the most spectacular one. The South Shelfand Island owe their existence to a subduction related volcanism which is perhaps 5-10 times older than the age of Orca and the other seamounts along the central basin of the Bransfield Strait.

Bottom sediment of the Western Baltic Sea - sheet Darß

The sheet "Darß" of the Western Baltic sediment distribution map displays several features of the late- and postglacial sediments in the area between 54°00? and 54°30? northern latitude and 12°00? and 13°00? eastern longitude on a scale of 1: 100,000. The main map shows the surface deposits in this area. Special attention is given to a detailed presentation of the granulometric characteristics of the sandy sedimens which are prevailing here. For this purpose a new way of visualization of grain size data was developed. Six insets provide information on water depth, positions of the sampling sites, areal distribution of median and sorting of sands, depth of the till surface thickness of the late- and postglacial sediments on top of the uppermost till and the bathymetry.

Mapping the Antarctic Polar Front: Weekly realizations from 2002 to 2014, links to NetCDF file and MPEG4 movie

We map the weekly position of the Antarctic Polar Front (PF) in the Southern Ocean over a 12-year period (2002-2014) using satellite sea surface temperature (SST) estimated from cloud-penetrating microwave radiometers. Our study advances previous efforts to map the PF using hydrographic and satellite data and provides a unique realization of the PF at weekly resolution across all longitudes. The mean path of the PF is asymmetric; its latitudinal position spans from 44 to 64° S along its circumpolar path. SST at the PF ranges from 0.6 to 6.9 °C, reflecting the large spread in latitudinal position. The average intensity of the front is 1.7 °C per 100 km, with intensity ranging from 1.4 to 2.3 °C per 100 km. Front intensity is significantly correlated with the depth of bottom topography, suggesting that the front intensifies over shallow bathymetry. Realizations of the PF are consistent with the corresponding surface expressions of the PF estimated using expendable bathythermograph data in the Drake Passage and Australian and African sectors. The climatological mean position of the PF is similar, though not identical, to previously published estimates. As the PF is a key indicator of physical circulation, surface nutrient concentration, and biogeography in the Southern Ocean, future studies of physical and biogeochemical oceanography in this region will benefit from the provided data set.