Average compositions and analyses range for clinopyroxene, olivines, orthopyroxene, and spinel from the MARK area at DSDP Site 45-395A, and ODP Site 153-920

Mineral compositions of residual peridotites collected at various locations in the Mid-Atlantic Ridge south of the Kane transform (MARK area) are consistent with generally smaller degrees of melting in the mantle near the large offset Kane transform than near the other, small offset, axial discontinuities in the area. We propose that this transform fault effect is due to along-axis variations in the final depth of melting in the subaxial mantle, reflecting the colder thermal regime of the ridge near the Kane transform. Calculations made with a passive mantle flow regime suggest that these along-axis variations in the final depth of melting would not produce the full range of crustal thickness variations observed in the MARK area seismic record. It is therefore likely that the transform fault effect in the MARK area is combined with other mechanisms capable of producing crustal thickness variations, such as along-axis melt migration, the trapping of part of the magma in a cold mantle root beneath the ridge, or active mantle upwelling.

Modelled global ocean temperature from 6 ka to present

We compare the ocean temperature evolution of the Holocene as simulated by climate models and reconstructed from marine temperature proxies. This site provides informations about the Holocene temperature trends as simulated by the models. We use transient simulations from a coupled atmosphere-ocean general circulation model, as well as an ensemble of time slice simulations from the Paleoclimate Modelling Intercomparison Project. The general pattern of sea surface temperature (SST) in the models shows a high latitude cooling and a low latitude warming. The proxy dataset comprises a global compilation of marine alkenone- and Mg/Ca-derived SST estimates. Independently of the choice of the climate model, we observe significant mismatches between modelled and estimated SST amplitudes in the trends for the last 6000 years. Alkenone-based SST records show a similar pattern as the simulated annual mean SSTs, but the simulated SST trends underestimate the alkenone-based SST trends by a factor of two to five. For Mg/Ca, no significant relationship between model simulations and proxy reconstructions can be detected. We tested if such discrepancies can be caused by too simplistic interpretations of the proxy data. We tested different seasons and depths in the model to compare the proxy data trends, and can reconcile only part of the mismatches on a regional scale. We therefore considered the additional environmental factor changes in the planktonic organisms' habitat depth and a time-shift in the recording season to diagnose whether invoking those environmental factors can help reconciling the proxy records and the model simulations. We find that invoking shifts in the living season and habitat depth can remove some of the model-data discrepancies in SST trends. Regardless whether such adjustments in the environmental parameters during the Holocene are realistic, they indicate that when modeled temperature trends are set up to allow drastic shifts in the ecological behavior of planktonic organisms, they do not capture the full range of reconstructed SST trends. Our findings indicate that climate model and reconstructed temperature trends are to a large degree only qualitatively comparable, thus providing a challenge for the interpretation of proxy data as well as the models' sensitivity to orbital forcing.

Nannofossil and stable isotope record across the Paleocene/Eocene Thermal Maximum in ODP Hole 183-1135A

The Paleocene/Eocene Thermal Maximum (PETM, ca. 55 Ma) is an abrupt, profound perturbation of climate and the carbon cycle associated with a massive injection of isotopically light carbon into the ocean-atmosphere system. As such, it provides an analogue for understanding the interplay between phytoplankton and climate under modern anthropogenic global-warming conditions. However, the accompanying enhanced dissolution poses uncertainty on the reconstruction of the affected ecology and productivity. We present a high-resolution record of bulk isotopes and nannofossil absolute abundance from Ocean Drilling Program (ODP) Site 1135 on the Kerguelen Plateau, Southern Indian Ocean to quantitatively constrain for the first time the influence of dissolution on paleoecological reconstruction. Our bulk-carbonate isotope record closely resembles that of the classic PETM site at ODP Site 690 on the opposite side of the Antarctic continent, and its correlation with those from ODP Sites 690, 1262 and 1263 records allows recognition of 14 precessional cycles upsection from the onset of the carbon isotopic excursion (CIE). This, together with a full range of common Discoasteraraneus and an abundance crossover between Fasciculithus and Zygrhablithusbijugatus, indicates the presence of the PETM at Site 1135, a poorly known record with calcareous fossils throughout the interval. The strong correlation between the absolute abundances of Chiasmolithus and coccolith assemblages reveals a dominant paleoecological signal in the poorly preserved fossil assemblages, while the influence of dissolution is only strong during the CIE. This suggests that r-selected taxa can preserve faithful ecological information even in the severely-altered assemblages studied here, and therefore provide a strong case for the application of nannofossils to paleoecological studies in better-preserved PETM sections. The inferred nannoplankton productivity drops abruptly at the CIE onset, but rapidly increases after the CIE peak, both of which may be driven by nutrient availability related to ocean stratification and vertical mixing due to changed sea-surface temperatures.

Long sedimentary records of sediment cores from the Chilean margin

The Antarctic Intermediate Water (AAIW) is a key player in global-scale oceanic overturning processes and an important conduit for heat, fresh water, and carbon transport. The AAIW past variability is poorly understood mainly due to the lack of sedimentary archives at intermediate water depths. We present records of benthic stable isotopes from sediments retrieved with the seafloor drill rig MARUM-MeBo at 956 m water depth off northern Chile (GeoB15016, 27°29.48'S, 71°07.58'W) that extend back to 970 ka. The sediments at this site are presently deposited at the boundary between AAIW and Pacific Deep Water (PDW). For previous peak interglacials, our results reveal similar benthic d13C values at site GeoB15016 and of a newly generated stack of benthic d13C from various deep Pacific cores representing the "average PDW." This suggests, unlike today, the absence of AAIW at the site and the presence of nearly pure PDW. In contrast, more positive d13C values at site GeoB15016 compared to the stack imply a considerable AAIW contribution during cold phases of interglacials and especially during glacials. Besides, we used three short sediment cores to reconstruct benthic d13C values from the AAIW core during the last glacial and found a d13C signature similar to today's. Assuming that this was the case also for the past 970 kyr, we demonstrate that sea level changes and latitudinal migrations of the AAIW formation site can only account for about 50% of the full range of past d13C increases at site GeoB15016 during cold periods. Other processes that could explain the remaining of the positive d13C anomalies are increases in glacial AAIW production and/or deeper convection of the AAIW with respect to preceding interglacials.

Seawater carbonate chemistry and hydrogen ions and carbonate chemistry in calcifying fluid of coral Astrangia poculata during experiments, 2011

A generalized physicochemical model of the response of marine organisms' calcifying fluids to CO2-induced ocean acidification is proposed. The model is based upon the hypothesis that some marine calcifiers induce calcification by elevating pH, and thus Omega aragonite, of their calcifying fluid by removing protons (H+). The model is explored through two end-member scenarios: one in which a fixed number of H+ is removed from their calcifying fluid, regardless of atmospheric pCO2, and another in which a fixed external-internal proton ratio ([H+]E/[H+]I) is maintained. The model is able to generate the full range of calcification response patterns observed in prior ocean acidification experiments and is consistent with the assertion that organisms' calcification response to ocean acidification is more negative for marine calcifiers that exert weaker control over their calcifying fluid pH. The model is empirically evaluated for the temperate scleractinian coral Astrangia poculata with in situ pH microelectrode measurements of the coral's calcifying fluid under control and acidified conditions. These measurements reveal that (1) the pH of the coral's calcifying fluid is substantially elevated relative to its external seawater under both control and acidified conditions, (2) the coral's [H+]E/[H+]I remains constant under control and acidified conditions, and (3) the coral removes fewer H+ from its calcifying fluid under acidified conditions than under control conditions. Thus, the carbonate system dynamics of A. poculata's calcifying fluid appear to be most consistent with the fixed [H+]E/[H+]I end-member scenario. Similar microelectrode experiments performed on additional taxa are required to assess the model's general applicability.

(Table S1) Age determination ofs ediment cores of the Azores Current System

In order to test the sensitivity of marine primary productivity in the midlatitude open ocean North Atlantic to changes in the Atlantic Meridional Overturning Circulation (AMOC), we investigated two spliced sediment cores from a site south of the Azores Islands at the northern rim of the North Atlantic subtropical gyre. For this purpose we analyzed coccolithophore assemblages, diatom abundances, alkenones and conducted X-ray fluorescence (XRF) core scanning. During times of reduced AMOC, especially during Heinrich event 1 (H1) and the Younger Dryas, we observe a strong increase in productivity as evidenced by high coccolith accumulation rates, high alkenone concentrations/accumulation rates, high Ba/Ti-ratios, high abundances of diatoms and low abundances ofF. profunda. The increased productivity is partly caused by a more southern position of the Azores Front (AzF), and hence by a less northward extension of the subtropical gyre, as deduced from high abundances of the temperate coccolithophore species G. muellerae and low abundances of subtropical species (Oolithotus spp., Umbellosphaera spp., Umbilicosphaeraspp.). However, to explain the full range of the observed productivity increase, other factors like increased westerly winds and advection of nutrient-rich surface waters have also to be considered. Because this pattern can also be observed in other sediment cores from the midlatitude North Atlantic, we propose that during times of reduced AMOC there has been a band of strongly increased productivity across the North Atlantic at the northern rim of the contracted subtropical gyre, which partly counteracts the decreased organic carbon pump in the high northern latitudes.

Global Ocean Colour for Carbon Cycle Research (full product set)

In 2005, the International Ocean Colour Coordinating Group (IOCCG) convened a working group to examine the state of the art in ocean colour data merging, which showed that the research techniques had matured sufficiently for creating long multi-sensor datasets (IOCCG, 2007). As a result, ESA initiated and funded the DUE GlobColour project (http://www.globcolour.info/) to develop a satellite based ocean colour data set to support global carbon-cycle research. It aims to satisfy the scientific requirement for a long (10+ year) time-series of consistently calibrated global ocean colour information with the best possible spatial coverage. This has been achieved by merging data from the three most capable sensors: SeaWiFS on GeoEye's Orbview-2 mission, MODIS on NASA's Aqua mission and MERIS on ESA's ENVISAT mission. In setting up the GlobColour project, three user organisations were invited to help. Their roles are to specify the detailed user requirements, act as a channel to the broader end user community and to provide feedback and assessment of the results. The International Ocean Carbon Coordination Project (IOCCP) based at UNESCO in Paris provides direct access to the carbon cycle modelling community's requirements and to the modellers themselves who will use the final products. The UK Met Office's National Centre for Ocean Forecasting (NCOF) in Exeter, UK, provides an understanding of the requirements of oceanography users, and the IOCCG bring their understanding of the global user needs and valuable advice on best practice within the ocean colour science community. The three year project kicked-off in November 2005 under the leadership of ACRI-ST (France). The first year was a feasibility demonstration phase that was successfully concluded at a user consultation workshop organised by the Laboratoire d'Océanographie de Villefranche, France, in December 2006. Error statistics and inter-sensor biases were quantified by comparison with insitu measurements from moored optical buoys and ship based campaigns, and used as an input to the merging. The second year was dedicated to the production of the time series. In total, more than 25 Tb of input (level 2) data have been ingested and 14 Tb of intermediate and output products created, with 4 Tb of data distributed to the user community. Quality control (QC) is provided through the Diagnostic Data Sets (DDS), which are extracted sub-areas covering locations of in-situ data collection or interesting oceanographic phenomena. This Full Product Set (FPS) covers global daily merged ocean colour products in the time period 1997-2006 and is also freely available for use by the worldwide science community at http://www.globcolour.info/data_access_full_prod_set.html. The GlobColour service distributes global daily, 8-day and monthly data sets at 4.6 km resolution for, chlorophyll-a concentration, normalised water-leaving radiances (412, 443, 490, 510, 531, 555 and 620 nm, 670, 681 and 709 nm), diffuse attenuation coefficient, coloured dissolved and detrital organic materials, total suspended matter or particulate backscattering coefficient, turbidity index, cloud fraction and quality indicators. Error statistics from the initial sensor characterisation are used as an input to the merging methods and propagate through the merging process to provide error estimates for the output merged products. These error estimates are a key component of GlobColour as they are invaluable to the users; particularly the modellers who need them in order to assimilate the ocean colour data into ocean simulations. An intensive phase of validation has been undertaken to assess the quality of the data set. In addition, inter-comparisons between the different merged datasets will help in further refining the techniques used. Both the final products and the quality assessment were presented at a second user consultation in Oslo on 20-22 November 2007 organised by the Norwegian Institute for Water Research (NIVA); presentations are available on the GlobColour WWW site. On request of the ESA Technical Officer for the GlobColour project, the FPS data set was mirrored in the PANGAEA data library.