Disentangling the effects of particles and circulation on 231Pa/230Th during Heinrich Stadials

It has been shown that during Heinrich stadials northern deep water production ceased leading to an enhanced inflow of southern sourced water. Although Heinrich events are not considered to represent the primary trigger of Heinrich stadials the reorganisation of Atlantic ocean dynamics during their occurrences is an active field of research. In particular, Heinrich stadial 2 (HS2) is of high interest, based on the observation that the interplay with the climate system was very different during HS2 compared to HS1, although the magnitude of iceberg and freshwater discharge was similar (Hemming, 2004). During HS2 sea-level was still decreasing while the atmospheric CO­2 content was relatively stable unlike the climatic evolution during Heinrich HS1.The notion of a reduced Atlantic Meridional Overturning Circulation (AMOC) during Heinrich Stadials is mainly strengthened by the 231Pa/230Th records from the Bermuda Rise. However, other influencing factors, capable of increasing the sedimentary 231Pa/230Th without according decreases in AMOC strength, need to be considered as well. Besides biogenic opal, high dust fluxes may also result in enhanced scavenging rate of both radionuclides and consequently higher sedimentary 231Pa/230Th signals, since another distinct feature that accompanies Heinrich Stadials is the high atmospheric concentration of dust in the northern hemisphere. Furthermore, high dust concentrations might be an indicator of a vigorous wind system and therefore strong ocean mixing, which can lead to the enhanced formation of nepheloid layers These layers are suspected to cause strong bottom scavenging and consequently high sedimentary 231Pa/230Th. Very high dust fluxes were observed e.g. during HS2 and MIS4. Here, we compare 231Pa/230Th with dust records in order to disentangle the effects of scavenging and circulation on the recorded sedimentary 231Pa/230Th from the northwestern Atlanti

GSH Attenuates Organ Injury and Improves Function after Transplantation of Fatty Livers

Ischemia-reperfusion injury (IRI) is increased after transplantation of steatotic livers. Since those livers are increasingly used for transplantation, protective strategies must be developed. Reactive oxygen species (ROS) play a key role in hepatic IRI. In lean organs, glutathione (GSH) is an efficient scavenger of ROS, diminishing IRI. The aim of this study was to evaluate whether GSH also protects steatotic allografts from IRI following transplantation. Fatty or lean livers were explanted from 10-week-old obese or lean Zucker rats and preserved (obese 4 h, lean 24 h) in hypothermic University of Wisconsin solution. Arterialized liver transplantation was then performed in lean syngeneic Zucker rats. Recipients of fatty livers were treated with GSH (200 mu mol/h/kg) or saline during reperfusion (2 h, n = 5). Parameters of hepatocellular damage and bile flow were measured. Transplantation of steatotic livers enhanced early reperfusion injury compared to lean organs as measured by increased aspartate aminotransferase, alanine aminotransferase, and lactate dehydrogenase plasma levels. Bile flow was also reduced in steatotic grafts. Intravenous administration of GSH effectively decreased liver damage in fatty allografts and resulted in improved bile flow. Intravenous application of GSH effectively reduces early IRI in steatotic allografts and improves recovery of these marginal donor organs following transplantation. Copyright (C) 2010 S. Karger AG, Base

Abrupt wind regime changes in the North Atlantic Ocean during the past 30,000-60,000 years

The inputs of higher plants in Blake Outer Ridge (subtropical western North Atlantic) during marine isotope stage 3 (MIS3) have been recorded at high resolution by quantification of C23–C33 odd carbon numbered n-alkanes and C20–C30 even carbon numbered n-alkan-1-ols in sediment sections of Ocean Drilling Program Site 1060. The changes of these proxies at this open marine site are mainly related to eolian inputs. Their concentrations and fluxes exhibit major abrupt variations that are correlated with Dansgaard/Oeschger (D/O) patterns in Greenland ice cores. The ratios between interstadials and stadials range between 2 and 9 times. The intense flux increases in the D/O stadials are linked to strong enhancements of the westerly wind regime at these subtropical latitudes during stadials. The observed variation was paralleled by changes in wind-blown dust and the polar circulation index in Greenland ice, which is in agreement with previously hypothesized atmospheric teleconnections between northern and middle-low latitudes of the Northern Hemisphere. The close correspondence between sedimentary and ice core proxies is evidence that crossings of the glacial climate thresholds involved major reorganizations of the troposphere. The observed large rise in higher plant biomarkers indicates that climate stabilization in the D/O stadial conditions led to main increases in wind intensity

Changes of the Atlantic meridional overturning circulation of the past 30ka recorded in a depth transect at the Blake Outer Ridge

Oceans and climate are a tightly coupled system interacting with each other in various ways such as storage of carbon dioxide in the deep ocean. Within the global conveyor belt the Atlantic Meridional Overturning Circulation (AMOC) holds a key function, transporting warm salty surface waters from the tropical to the northern Atlantic where deep water formation takes place. Following the continental rise of North America this newly formed deep water propagates southward as Western Boundary Undercurrent (WBUC) ventilating the deep Atlantic. In the past (e.g. the last glacial cycle) strength and geometry of the AMOC have changed significantly. This study aims to provide a better understanding of the temporal and spatial (also depth depended) evolution of the AMOC in the western Atlantic sector since the last glacial (∼30 ka). We have investigated four sediment cores of the Blake Outer Ridge (30°N, 74°W; ODP 1059 to 1062) in a depth transect from 3000 to 4700 m water depth in the main flow path of the WBUC. We measured four down-core profiles of neodymium (εNd) and 231Pa/230Th isotopes for the reconstruction of water mass provenance and circulation strength of the last ∼30 ka. In contrast to published Nd isotope and 231Pa/230Th records from the Blake Ridge area our records are of unprecedented resolution, resolving climate key features of the North Atlantic region: Heinrich Stadials (HS) 1 and 2, the Last Glacial Maximum (LGM), the Bølling-Allerød and Younger Dryas (YD). Radiogenic Nd isotope signatures during the LGM reveal AABW to be the prevalent water mass in the deep western North Atlantic. The trend to more unradiogenic signatures during the deglaciation point to an increased formation of NADW which was again replaced by AABW during YD. The Holocene shows the most unradiogenic signatures and therefore established NADW. The circulation strength-proxy 231Pa/230Th indicates reduced LGM deep circulation, a pronounced slowdown during HS1 and a strong and deep circulation during the Holocene. Compared to isotopic records from the Bermuda Rise (ODP 1063) we found depth depended geometry changes of the WBUC which have occurred through the last glacial. Here, we focus on how deep northern sourced water has reached during phases of reduced circulation (indicated by increased 231Pa/230Th ratios) and the timing of this southward progradation of lower NADW

IODP Expedition 361 – Southern African Climates and Agulhas LGM Density Profile

IODP Expedition 361 drilled six sites (U1474 – U1479) on the southeast African margin and the Indian-Atlantic ocean gateway from 30 January to 31 March 2016. The sites, situated in the Mozambique Channel, Natal Valley, Agulhas Plateau, and Cape Basin, were targeted to reconstruct the history of the Greater Agulhas Current System over the past ~5 Ma. More specifically, the main objectives of Expedition 361 were: (i) to establish the sensitivity of the Agulhas Current to climate change during the Plio-Pleistocene in association with transient to long-term changes of high-latitude climates, tropical heat budgets, and the monsoon system; (ii) to determine the dynamics of the Indian-Atlantic gateway circulation in association with changing wind fields and migrating ocean fronts; (iii) to examine the connection of the Agulhas leakage and the Atlantic Meridional Overturning Circulation; (iv) to address the influence of the Agulhas Current on African terrestrial climates, notably rainfall patterns and river runoff, and potential links to hominid evolution. Additionally, the expedition set out to fulfill the needs of the Ancillary Project Letter, consisting of high-resolution interstitial water samples aiming at constraining the temperature and salinity profiles of the ocean during the Last Glacial Maximum. In total, 5175 m of core was recovered (average recovery 102 %) from a region poorly represented in the database of drill sites for scientific purposes. Physical property records derived from core-logging of the recovered sequences allowed complete spliced stratigraphic sections to be generated that span the interval of 0 to between ~0.13 and 7 Ma. A high-resolution program of interstitial water samples was carried out at Sites U1474, U1475, U1476, and U1478. The expedition made major strides toward fulfilling the scientific objectives despite of ~11 days of lost operational time due to weather conditions, a medical evacuation, and delays in attaining the necessary permissions to operate in Mozambique exclusive economic zone waters. Site U1474 (3034 meters below sea level [mbsl]), located in the northernmost Natal Valley, consists of eight holes ranging in penetration depth from 3.1 to 254.1 m drilling depth below seafloor (dsf). A total of 910.8 m of sediment was recovered, predominantly consisting of foraminifer-bearing clay with nannofossils. Based on the shipboard bio- and magnetistratigraphic datums, the sedimentary sequence extends back to the late Miocene (~6.2 Ma). This record represents the only site situated beneath the main flow of the fully constituted Agulhas Current and therefore provides the opportunity for high-resolution climate reconstructions of Agulhas Current warm-water transports and upstream variability that may allow the identification of connections between Agulhas leakage and its headwater variability. It also holds significant potential to investigate the connections between southern African terrestrial climates and southeast Indian Ocean heat budgets and the links to the cultural evolution of early modern humans. Site U1475 (2669 mbsl), located on the southwestern flank of the Agulhas Plateau, consists of six holes ranging in penetration depth from 1.5 to 277.0 m dsf. A total of 1015.9 m of sediment was recovered, predominantly consisting of nannofossil ooze. Shipboard bio- and magnetistratigraphic data suggest that the sedimentary sequence extends back to the late Miocene (~7 Ma). This record provides the opportunity for high-resolution climate reconstructions of the Agulhas Return Current and connections with the Sub-Tropical Front, productivity, and deep-water circulation. Site U1476 (2165 mbsl), located at the northern entrance of the Mozambique Channel, consists of five holes ranging in penetration depth from 5.7 to 234.8 m dsf. A total of 873.8 m of sediment was recovered, predominantly consisting of foraminifer-rich nannofossil ooze. The sedimentary sequence extends back to the late Miocene (~6.9 Ma), as inferred from the shiboard bio- and magnetostratigraphic data. The site boasts excellent biostratigraphy and notably cyclic physical properties. It therefore provides the opportunity for high-resolution reconstructions of tropical faunal assemblages, which will allow identification of connections be¬tween Agulhas leakage and its headwater variability. It also holds significant potential to investigate the connections between southern African terrestrial climates and southeast Indian Ocean heat budgets and thermocline and deep-water variability with likely links to the development of the Indonesian Throughflow as well as aridification of east Africa. Because of the excellent preservation of foraminifers, this an ideal site for a long record of surface-ocean pH from boron isotopes. Site U1477 (429 mbsl), located in the western Mozambique Channel east of the Zambezi River delta, consists of three holes ranging in penetration depth from 119.4 to 181.2 m dsf. A total of 490.0 m of sediment was recovered, predominantly consisting of sandy clay with foraminifers and nannofossils. Based on correlations to a nearby 14C dated cores and two biostratigrahic markers, the sedimentary sequence extends back to the Late Pleistocene (~0.13 Ma). The extreme accumulation rate (~1 m/ky) at this site provides the opportunity for exceptionally high resolution reconstructions of terrestrial climate and thermocline characteristics during the last glacial cycle. Site U1478 (488 mbsl), located in the western Mozambique Channel east of the Limpopo River delta, consists of four holes ranging in penetration depth from 216.0 to 248.4 m dsf. A total of 922.1 m of sediment was recovered, predominantly consisting of sand or clayey/sandy silt with foraminifers and nannofossils. The shipboard age-model suggests that the sedimentary sequence extends back to the Pliocene (~4 Ma). This record provides the opportunity for high-resolution climate reconstructions of faunal, biogeochemical, and terrigenous tracers that are characteristic of the upper reaches of the Agulhas Current warm-water transports that will allow connections between Agul¬has leakage and its headwater variability. The site also holds significant potential to investigate the connections between southern African terrestrial climates and southeast Indian Ocean heat budgets, and examine the relationship between such climate variability and early human evolution. Site U1479 (2615 mbsl), located in Cape Basin, consists of nine holes ranging in penetration depth from 1.0 to 300.7 m dsf. A total of 963.1 m of sediment was recovered, predominantly consisting of nannofossil ooze with or without foraminifers. According to the shipboard bio- and magnetostratigraphy-based age model, the sedimentary sequence extends back to the late Miocene (~7 Ma). This record represents the only site situated in the immediate Agulhas leakage pathway. It will therefore provide the opportunity for high-resolution climate reconstructions of the leakage and temporal comparisons with deep-water circulation

Millennial-scale deep ocean ventilation and sea-surface variability during the last four glacial cycles : a new assessment for the Northern Hemisphere ice-sheet growth

AGU Fall Meeting, S. Francisco (USA), 19-14 December 2007, Suppl., Abstract PP44B-0

Direct imprinting of organic-inorganic hybrid materials into high aspect ratio sub-100nm structures

The challenging fabrication of sub-100-nm structures with high aspect ratio by UV-nanoimprint lithography (NIL) is addressed in this work. Thermal shrinkage is induced by cooling the structures below room temperature to avoid the issues commonly arising during the release of the polymeric nanostructures from the master. The UV-NIL has been performed to obtain OrmoComp® nanostructures using OrmoStamp® working stamps copied from Si masters. Nanoridges and nanopillars with 45nm width and 380nm thickness have been fabricated with a corresponding aspect ratio of 8.5. This is, to the best of our knowledge, the highest aspect ratio achieved using organic-inorganic hybrid materials at the sub-100-nm scale

VSHOT: a tool for characterizing large, imprecise reflectors

A prototype Video Scanning Hartmann Optical Tester (VSHOT) has been developed to characterize the optics of dish-type solar concentrators. VSHOT is a flexible platform that may characterize any large reflector with a focal length over diameter ratio (f{number_sign}) greater than 0. 45, and RMS optical error in the 0. I - I 0 milliradian range. The VSHOT hardware, software, and operation are described. Measurement uncertainty and preliminary test results are discussed. Another potential application being explored for the VSHOT is the quality assurance of slumped-glass automobile windshields. Preliminary test results from a reference optic and a section of a windshield are presented

Expedition 306 summary

The overall aim of the North Atlantic paleoceanography study of Integrated Ocean Drilling Program Expedition 306 is to place late Neogene–Quaternary climate proxies in the North Atlantic into a chronology based on a combination of geomagnetic paleointensity, stable isotope, and detrital layer stratigraphies, and in so doing generate integrated North Atlantic millennial-scale stratigraphies for the last few million years. To reach this aim, complete sedimentary sections were drilled by multiple advanced piston coring directly south of the central Atlantic “ice-rafted debris belt” and on the southern Gardar Drift. In addition to the North Atlantic paleoceanography study, a borehole observatory was successfully installed in a new ~180 m deep hole close to Ocean Drilling Program Site 642, consisting of a circulation obviation retrofit kit to seal the borehole from the overlying ocean, a thermistor string, and a data logger to document and monitor bottom water temperature variations through time