Description: Ice core records demonstrate a glacial–interglacial atmospheric CO2 increase of ~ 100 ppm, while 14C calibration efforts document a strong decrease in atmospheric 14C concentration during this period. A calculated transfer of ~ 530 Gt of 14C-depleted carbon is required to produce the deglacial coeval rise of carbon in the atmosphere and terrestrial biosphere. This amount is usually ascribed to oceanic carbon release, although the actual mechanisms remained elusive, since an adequately old and carbon-enriched deep-ocean reservoir seemed unlikely. Here we present a new, though still fragmentary, ocean-wide Δ14C data set showing that during the Last Glacial Maximum (LGM) and Heinrich Stadial 1 (HS-1) the maximum 14C age difference between ocean deep waters and the atmosphere exceeded the modern values by up to 1500 14C yr, in the extreme reaching 5100 14C yr. Below 2000 m depth the 14C ventilation age of modern ocean waters is directly linked to the concentration of dissolved inorganic carbon (DIC). We propose as a working hypothesis that the modern regression of DIC vs. Δ14C also applies for LGM times, which implies that a mean LGM aging of ~ 600 14C yr corresponded to a global rise of ~ 85–115 μmol DIC kg−1 in the deep ocean. Thus, the prolonged residence time of ocean deep waters may indeed have made it possible to absorb an additional ~ 730–980 Gt DIC, one third of which possibly originated from intermediate waters. We also infer that LGM deep-water O2 dropped to suboxic values of 〈 10 μmol kg−1 in the Atlantic sector of the Southern Ocean, possibly also in the subpolar North Pacific. The deglacial transfer of the extra-aged, deep-ocean carbon to the atmosphere via the dynamic ocean–atmosphere carbon exchange would be sufficient to account for two trends observed, (1) for the increase in atmospheric CO2 and (2) for the 190‰ drop in atmospheric Δ14C during the so-called HS-1 "Mystery Interval", when atmospheric 14C production rates were largely constant

Description: Ocean Drilling Program (ODP) Site 982 provided a key sediment section at Rockall Plateau for reconstructing northeast Atlantic paleoceanography and monitoring benthic δ18O stratigraphy over the late Pliocene to Quaternary onset of major Northern Hemisphere glaciation. A renewed hole-specific inspection of magnetostratigraphic reversals and the addition of epibenthic δ18O records for short Pliocene sections in holes 982A, B, and C, crossing core breaks in the δ18O record published for Hole 982B, now imply a major revision of composite core depths. After tuning to the orbitally tuned reference record LR04, the new composite δ18O record results in a hiatus, where the Kaena magnetic subchron might have been lost, and in a significant age reduction for all proxy records by 130 to 20 ky over the time span 3.2–2.7 million years ago (Ma). Our study demonstrates the general significance of reliable composite-depth scales and δ18O stratigraphies in ODP sediment records for generating ocean-wide correlations in paleoceanography. The new concept of age control makes the late Pliocene trends in SST (sea surface temperature) and atmospheric pCO2 at Site 982 more consistent with various paleoclimate trends published from elsewhere in the North Atlantic.

Description: Great Belt, Vejsnäs Rinne and Boknis Rinne form a major interconnected channel System of approximately 80 km length and 30 m depth on the Kiel Bay sea floor, which generally is only some 10 to 20 m deep. 1971 to 1973, 32 transects were sampled across the channel slopes using narrow Station distances and systematically adding data (T°, S°/oo) from 5 hydrographic cross sections over a one and a half year period. A quantitative, combined study of the molluscan fauna, dead shells and Sediments yielded the following results. 30 species of bivalves and 19 of gastropods were sampled as livingspecimens. According to their long life span, Cypritta islandica is dominant in the deep and the Astarte species on the upper part of the channel slope. Macoma baltica is dominantin a third, more shallow Zone, which is actually outside of the channels. Abra alba is the most persistent species of the channels being present in 86% of all samples. Except for Hydrobia, gastropods display low numbers of presence and abundance and are almost never dominant. The bottom level of the thermohaline pycnocline impinges on the channel slope as a rule between (15-)18 and 22 (-25) m depth. This boundary layer is clearly reflected by the fauna, i.e. by maximum numbers of species and species richness, of species presence and abundance, as well as of the biomass of total molluscs and of most of the single mollusc species. The faunal Optimum is explained by the favourable combination of a suite of factors, such as relatively stable temperatures and increased salinity, sufficient aeration, and a strong “rain” of larvae and nutrition where the upper water mass is barred by the pycnocline. Substrate conditions (± 50 % of Sediment 〈 63 p) might be favourable as well. The deeper water mass of the channel System is increasingly plumbed by the pycnocline and correspondingly poor in oxygen concentration towards the inner end of the bay. The oxygen deficiency more and more confines the Optimum beit of the molluscs from below, and causes a distinct elevation of the maximum numbers of species, species richness, species dominance and biomass from the entrance towards the inner part of the bay from 20-24 to 15 -20 m depth. Increasing distance from the bay ’s entrance , (the Great Belt) does not exert any other influence on the molluscan fauna. Averaging the whole transects, the mean numbers of species, species richness, species presence and biomass stay constant in line with constant T-S conditions. The molluscan Optimum belt is widened on the slope towards the deep and partly doubled at current and water exposed parts of the slope, where it also achieves its absolute maximum numbers. No molluscan species is bound to a specific type of Sediment, though eventually certain Sediments may be preferred. Mud forms an exception in showing a clear decrease of the number of specimens (by an overlap with the factor oxygen deficiency). Except for the well known general reduction of species in the Kiel Bay, the distribution pattern of temp erature and salinity exerts only minor influences on the fauna. The dead-shell species as semblage generally reflects the living one. On the whole, they correspond with their composition of species, the zonation of dominant species (middle, emergent Astarte beit) and the distribution and elevation pattern of the maxima of species, species richness and dead-shell quantities. A downslope transport of shells is inferred, among other things, from a stronger presence of (dead-shell) species in the deeper part of the channel. As measured by the lateral displacement of the mollusc maximum belts, the transport amounts 1 to 3 m in vertical distance, rarely up to 7 m at current exposed slopes. These numbers correspond to 30-75 m horizontal distance. Besides currents, extreme wave action is a possible cause. Current induced long-distance transport of dead shells generates increased numbers of species, species presence and dead-shell quantities at the channel bottom, especially behind narrow passes. Hotvever, taking into account the undisturbed distribution of dominant species, the quantity of reworked shells must be insignificant. First indications of the shell production can be derived from the living-dead ratio of shell samples — notwithstanding the varying amounts of carbonate dissolution. For instance, the production of Astarte species is some 13 times smaller than the one of Abra alba and 7 times smaller than that of Cyprina islandica. — A general strong change from living to dead-shell dominance occurs below the pycnocline at 20 to 24 m depth. In the case of a fossil analogue of a Baltic Sea channel, marked shell horizons with a broad species spectrum most probably correspond to a molluscan zone at the level of the mean pycnocline Position.

Description: Deep water formation in the North Atlantic and Southern Ocean is widely thought to influence deglacial CO2 rise and climate change; here we suggest that deep water formation in the North Pacific may also play an important role. We present paired radiocarbon and boron isotope data from foraminifera from sediment core MD02-2489 at 3640 m in the North East Pacific. These show a pronounced excursion during Heinrich Stadial 1, with benthic-planktic radiocarbon offsets dropping to ~350 years, accompanied by a decrease in benthic d11B. We suggest this is driven by the onset of deep convection in the North Pacific, which mixes young shallow waters to depth, old deep waters to the surface, and low-pH water from intermediate depths into the deep ocean. This deep water formation event was likely driven by an increase in surface salinity, due to subdued atmospheric/monsoonal freshwater flux during Heinrich Stadial 1. The ability of North Pacific Deep Water (NPDW) formation to explain the excursions seen in our data is demonstrated in a series of experiments with an intermediate complexity Earth system model. These experiments also show that breakdown of stratification in the North Pacific leads to a rapid ~30 ppm increase in atmospheric CO2, along with decreases in atmospheric d13C and D14C, consistent with observations of the early deglaciation. Our inference of deep water formation is based mainly on results from a single sediment core, and our boron isotope data are unavoidably sparse in the key HS1 interval, so this hypothesis merits further testing. However we note that there is independent support for breakdown of stratification in shallower waters during this period, including a minimum in d15N, younging in intermediate water 14C, and regional warming. We also re-evaluate deglacial changes in North Pacific productivity and carbonate preservation in light of our new data, and suggest that the regional pulse of export production observed during the Bølling-Allerød is promoted by relatively stratified conditions, with increased light availability and a shallow, potent nutricline. Overall, our work highlights the potential of NPDW formation to play a significant and hitherto unrealized role in deglacial climate change and CO2 rise.