Tomographic measurements of O. umbonatus and N. truempyi during the PETM and ETM-2 at ODP Sites 208-1262 and 208-1263

Predicting the impact of ongoing anthropogenic CO2 emissions on calcifying marine organisms is complex, owing to the synergy between direct changes (acidification) and indirect changes through climate change (e.g., warming, changes in ocean circulation, and deoxygenation). Laboratory experiments, particularly on longer-lived organisms, tend to be too short to reveal the potential of organisms to acclimatize, adapt, or evolve and usually do not incorporate multiple stressors. We studied two examples of rapid carbon release in the geological record, Eocene Thermal Maximum 2 (~53.2 Ma) and the Paleocene Eocene Thermal Maximum (PETM, ~55.5 Ma), the best analogs over the last 65 Ma for future ocean acidification related to high atmospheric CO2 levels. We use benthic foraminifers, which suffered severe extinction during the PETM, as a model group. Using synchrotron radiation X-ray tomographic microscopy, we reconstruct the calcification response of survivor species and find, contrary to expectations, that calcification significantly increased during the PETM. In contrast, there was no significant response to the smaller Eocene Thermal Maximum 2, which was associated with a minor change in diversity only. These observations suggest that there is a response threshold for extinction and calcification response, while highlighting the utility of the geological record in helping constrain the sensitivity of biotic response to environmental change.

Geochemistry and isotopes at DSDP Site 68-503

Nodules occur in the siliceous calcareous ooze and siliceous marl at Site 503 in the eastern equatorial Pacific. They are present below a depth of about 11 meters throughout the green-colored reduced part of the section down to 228 meters, although they are most abundant between 30 and 85 meters. They are cylindrical or barrel-shaped, up to 70 mm long, and usually have an axial channel through them or are hollow. They appear to have formed around and/or within burrows. XRD studies and microprobe analyses show that they are homogeneous and consist of calcian rhododrosite and minor calcite; Mn is present to the extent of about 30%. Isotopic analyses of the carbonate give carbon values which range from -1.2 per mil to -3.8 per mil, and oxygen isotope compositions vary from +4.0 per mil to +6.0 per mil. These values are different from those for marine-derived carbonates as exemplified by the soft sediment filling of a burrow: d13C, -0.26 per mil; d18O, +1.05 per mil. The carbon isotope data indicate that carbonate derived (possibly indirectly) from seawater was mixed with some produced by organic diagenesis to form the nodules. The d18O values suggest that although they formed near the sediment surface, some modification or the introduction of additional diagenetic carbonate occurred during burial.

Secchi depth maps for the Baltic Sea, 2003-2012, with links to GeoTIFs

Secchi depth is a measure of water transparency. In the Baltic Sea region, Secchi depth maps are used to assess eutrophication and as input for habitat models. Due to their spatial and temporal coverage, satellite data would be the most suitable data source for such maps. But the Baltic Sea's optical properties are so different from the open ocean that globally calibrated standard models suffer from large errors. Regional predictive models that take the Baltic Sea's special optical properties into account are thus needed. This paper tests how accurately generalized linear models (GLMs) and generalized additive models (GAMs) with MODIS/Aqua and auxiliary data as inputs can predict Secchi depth at a regional scale. It uses cross-validation to test the prediction accuracy of hundreds of GAMs and GLMs with up to 5 input variables. A GAM with 3 input variables (chlorophyll a, remote sensing reflectance at 678 nm, and long-term mean salinity) made the most accurate predictions. Tested against field observations not used for model selection and calibration, the best model's mean absolute error (MAE) for daily predictions was 1.07 m (22%), more than 50% lower than for other publicly available Baltic Sea Secchi depth maps. The MAE for predicting monthly averages was 0.86 m (15%). Thus, the proposed model selection process was able to find a regional model with good prediction accuracy. It could be useful to find predictive models for environmental variables other than Secchi depth, using data from other satellite sensors, and for other regions where non-standard remote sensing models are needed for prediction and mapping. Annual and monthly mean Secchi depth maps for 2003-2012 come with this paper as Supplementary materials.

Deep water formation in the North Pacific and deglacial CO2 rise

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.

Geochemistry of Lesser Antilles lavas

We present new U-series disequilibrium and radiogenic isotope data for 7 mafic lavas from the Lesser Antilles arc. These are combined with published data in an internally consistent model that quantitatively estimates the amount of sediment and fluid added to the source of the Lesser Antilles arc system. Some lavas form an array consistent with bulk sediment addition (0.2-2%) whereas others appear to require addition of 0.4-2% sediment melt, particularly in the south of the arc. Evidence for both bulk sediment and sediment melt addition can be found within both the northern and central sections of the arc suggesting a thermal structure whereby the upper portions of the subducted sediment pile lie close to their solidus beneath much of the arc. Addition of up to 5% fluid derived from altered oceanic crust to these sediment enriched mantle wedge source regions can simulate the majority of the lavas on a plot of 207Pb/204Pb versus Ce/Pb. By taking into account the range in calculated wedge compositions and allowing for some mobility of Th in the fluid, the same model can also account for much of the observed range of U-Th-Ra disequilibria, especially if the eclogitic residue contains trace amounts of rutile. The implication of this more complex model is that the time scales for fluid addition and differentiation could be significantly shorter than those estimated in some previous studies.

Geochemistry of sediment cores from the Rainbow vent site

A geochemical investigation was carried out on two sediment cores collected at 2 and 5 km from the Rainbow hydrothermal vent site. Bulk sediment compositions indicate that these cores record clear enrichments in Fe, Cu, Mn, V, P and As from hydrothermal plume fallout (Cave et al., 2002, doi:10.1016/S0016-7037(02)00823-2). Sequential dissolution of the bulk sediments has been used to discriminate between a leach (biogenic and oxy-hydroxide) component and a residual phase (detrital and sulphide/sulphate fractions). Major element data (Al, Fe, Ti, Mn, Mg, Ca, Si and index%) reveal that the hydrothermal input, as recorded in the leach phase, is much stronger than apparent from bulk sediment analyses alone. REE patterns for the leach phase record contributions from both biogenic carbonate (mimicking seawater REE patterns) and hydrothermal oxy-hydroxides, with the latter exhibiting positive Eu anomalies (hydrothermal derived) and negative Ce anomalies (seawater derived). Based on major element and REE data, the residue contains contributions from aeolian dust input, local MORB material and a hydrothermal component. Ternary REE mixing calculations indicate that most of the REE within the residual fraction (~80%) is derived from hydrothermal material, while detrital contributions to the REE budget, as deep-sea clay and volcanic debris, are <20%. By combining bulk and REE data for the various end-member components of the residue, we calculate that the chemical composition of the residue hydrothermal end-member is high in Ca (6-15%) and with a Nd/Sr ratio of 0.004. These characteristics indicate the presence of low-solubility hydrothermal sulphate (rather than sulphide) material within the residue component of Rainbow hydrothermal sediments.

Fig. S1. Loci of possible event locations based on differential ts - tp arrival times at the single functioning geophone

Geological storage of CO2 that has been captured at large, point source emitters represents a key potential method for reduction of anthropogenic greenhouse gas emissions. However, this technology will only be viable if it can be guaranteed that injected CO2 will remain trapped in the subsurface for thousands of years or more. A signi?cant issue for storage security is the geomechanical response of the reservoir. Concerns have been raised that geomechanical deformation induced by CO2 injection will create or reactivate fracture networks in the sealing caprocks, providing a pathway for CO2 leakage. In this paper, we examine three large-scale sites where CO2 is injected at rates of ab. 1 megatonne/y or more: Sleipner, Weyburn, and In Salah. We compare and contrast the observed geomechanical behavior of each site, with particular focus on the risks to storage security posed by geomechanical deformation. At Sleipner, the large, high-permeability storage aquifer has experienced little pore pressure increase over 15 y of injection, implying little possibility of geomechanical deformation. At Weyburn, 45 y of oil production has depleted pore pressures before increases associated with CO2 injection. The long history of the ?eld has led to complicated, sometimes nonintuitive geomechanical deformation. At In Salah, injection into the water leg of a gas reservoir has increased pore pressures, leading to uplift and substantial microseismic activity. The differences in the geomechanical responses of these sites emphasize the need for systematic geomechanical appraisal before injection in any potential storage site.

Geochemistry of Mid-Atlantic Ridge sediments

Geochemical compositions and Sr and Nd isotopes were measured in two cores collected ~2 and 5 km from the Rainbow hydrothermal vent site on the Mid-Atlantic Ridge. Overall, the cores record enrichments in Fe and other metals from hydrothermal fallout, but sequential dissolution of the sediments allows discrimination between a leach phase (easily leachable) and a residue phase (refractory). The oxy-anion and transition metal distribution combined with rare earth element (REE) patterns suggest that (1) the leach fraction is a mixture of biogenic carbonate and hydrothermal Fe-Mn oxy-hydroxide with no significant contribution from detrital material and (2) >99.5% of the REE content of the leach fraction is of seawater origin. In addition, the leach fraction has an average 87Sr/86Sr ratio indistinguishable from modern seawater at 0.70916. Although we lack the epsilon-Nd value of present-day deep water at the Rainbow vent site, we believe that the REE budget of the leach fraction is predominantly of seawater origin. We suggest therefore that the leach fraction provides a record of local seawater epsilon-Nd values. Nd isotope data from these cores span the period of 4-14 ka (14C ages) and yield epsilon-Nd values for North East Atlantic Deep Water (NEADW) that are higher (-9.3 to -11.1) than those observed in the nearby Madeira Abyssal Plain from the same depth (-12.4 ± 0.9). This observation suggests that either the Iceland-Scotland Overflow Water (ISOW) and Lower Deep Water contributions to the formation of NEADW are higher along the Mid-Atlantic Ridge than in the surrounding basins or that the relative proportion of ISOW was higher during this period than is observed today. This study indicates that hydrothermal sediments have the potential to provide a higher-resolution record of deep water epsilon-Nd values, and hence deepwater circulation patterns in the oceans, than is possible from other types of sediments.

Carbonate chemistry, community metabolism, PAR, temperature and salinity of One Tree Island reef

There are few in situ studies showing how net community calcification (Gnet) of coral reefs is related to carbonate chemistry, and the studies to date have demonstrated different predicted rates of change. In this study, we measured net community production (Pnet), Gnet, and carbonate chemistry of a reef flat at One Tree Island, Great Barrier Reef. Diurnal pCO2 variability of 289-724 µatm was driven primarily by photosynthesis and respiration. The reef flat was found to be net autotrophic, with daily production of ? 35 mmol C/m**2/d and net calcification of ? 33 mmol C/m**2/d . Gnet was strongly related to Pnet, which drove a hysteresis pattern in the relationship between Gnet and aragonite saturation state (Omega ar). Although Pnet was the main driver of Gnet, Omega ar was still an important factor, where 95% of the variance in Gnet could be described by Pnet and Omega ar. Based on the observed in situ relationship, Gnet would be expected to reach zero when Omega ar is 2.5. It is unknown what proportion of a decline in Gnet would be through reduced calcification and what would occur through increased dissolution, but the results here support predictions that overall calcium carbonate production will decline in coral reefs as a result of ocean acidification.