Description: We present a global atlas of downcore foraminiferal oxygen and carbon isotope ratios available at https://doi.org/10.1594/PANGAEA.936747 (Mulitza et al., 2021a). The database contains 2106 published and previously unpublished stable isotope downcore records with 361 949 stable isotope values of various planktic and benthic species of Foraminifera from 1265 sediment cores. Age constraints are provided by 6153 uncalibrated radiocarbon ages from 598 (47 %) of the cores. Each stable isotope and radiocarbon series is provided in a separate netCDF file containing fundamental metadata as attributes. The data set can be managed and explored with the free software tool PaleoDataView. The atlas will provide important data for paleoceanographic analyses and compilations, site surveys, or for teaching marine stratigraphy. The database can be updated with new records as they are generated, providing a live ongoing resource into the future.

Description: NORP-SORP Workshop on Polar Fresh Water: Sources, Pathways and Impacts of Freshwater in Northern and Southern Polar Oceans and Seas (SPICE-UP)What: Up to 60 participants at a time and more than twice as many registrants in total from 20 nations and across experience levels met to discuss the current status of research on freshwater in both polar regions, future directions, and synergies between the Arctic and Southern Ocean research communitiesWhen: 19-21 September 2022 Where: Online

Description: Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution June 1990

Description: A recently developed technique for determining past sea surface temperatures (SST), based on an analysis of the unsaturation ratio of long chain C37 methyl alkenones (Uk37) produced by Prymnesiophyceae phytoplankton, has been applied to late Quaternary sediment cores. Previous studies have shown that the Uk37 ratio of these alkenones is linearly proportional to the sea-water temperature in which the plankton grow, both in culture and water column samples. Furthermore, a reasonable correlation has been found between open ocean paleo-SST estimates based on Uk37 values and those derived from δ180, for the period spanning approximately the last 100,000 years (Brassell, 1986b). These results indicate this technique has potential for determining paleo-SST from analysis of alkenones extracted from marine sediments. In order to apply the Uk37 method quantitatively, it is necessary to calibrate the method for sediment samples, and to assess how well the alkenones maintain their temperature signal under some common conditions of sediment deposition and sample handling. It is also necessary to determine the method's usefulness downcore, that is, back in time, by comparing it to established methods. This study examined the effect on Uk37 of conditions that cause dissolution of carbonates in the sediment, and methods of storage and 'sample handling. These are two problems that must be resolved before the method can be applied rigorously and quantitatively to sediments for paleotemperature estimations. A comparison of duplicate samples collected and stored frozen versus those stored at room temperature for up to four years showed no resolvable differences in Uk37. Laboratory experiments of carbonate dissolution indicated there is no effect on Uk37 values under the acidic conditions that dissolve carbonates. Initial field results support this, but indicate more studies are necessary. The Uk37 "thermometer" was calibrated by analyzing Uk37 in coretops from widely varying open ocean sites. Sediment values of Uk37 reflected overlying SST for the appropriate season of the phytoplankton bloom, which for this study was assumed to be summer in high latitudes. These results fall on the same regression line for culture and water column samples derived by Prahl and Wakeham (1987), indicating that their equation (Uk37 = 0.033 T + 0.043) is suitable for use in converting Uk37 values in sediments to overlying SST for the season of coccolith bloom. Using this calibration for sediments, the Uk37 paleotemperature method can be quantitatively applied down core to open ocean sediments. In the Equatorial Atlantic, Uk37 temperature estimates were compared to those obtained from δ18O of the planktonic foraminifer Globigerinoides sacculifer, and planktonic foraminiferal assemblages for the last glacial cycle. The alkenone method showed ~1.56°C cooling at the last glacial maximum. This is about half the decrease shown by both the isotopic method ( ~3.40°C) and foraminiferal assemblages (~3.75°C), implying that, if Uk37 estimates are correct, SST in the equatorial Atlantic was only reduced slightly in the last glaciation. In the Northeast Atlantic, Uk37 temperature estimates show a profile downcore which is similar to the estimates from foram assemblages but with a constant offset toward warmer values throughout the core. Uk37 SST estimates are substantially warmer than foraminiferal estimates at all times, which may indicate inaccuracy in Uk37 temperatures at this site. Uk37 indicates a SST of 12°C for the late glacial and 18°C for the Recent, whereas assemblages give estimates of 9°C and 13°C, respectively. At 12,700 yrs BP, the Uk37 and foram assemblage methods indicate a 2°C warming. A temperature change of 2°C can account for only 0.44°/oo of the observed 1.2°/oo δ18O signal, indicating that the additional 0.8°/oo change in δ18O must result from changes in surface salinity most likely due to a meltwater lid. Uk37 estimates show the major temperature shift from glacial to interglacial temperatures occured at about 9,000 yrs BP disagreeing with assemblage data which shows the shift to Holocene values at about 12,700 yrs BP. If Uk37 temperature estimates are accurate, this disagreement may reflect differing habitats of flora and fauna under the unusual sea surface conditions in this area during the deglaciation.

Description: Primary financial support for this research came from the Ocean Ventures Fund (grant 25/ 85.08), without which this project would not have been possible. Funding supporting the labs of John Farrington (OCE 88-11409) and Lloyd Keigwin (OCE 83-08893 and ATM 84-14335) in which I worked also provided funding for part for this research.

Description: Author Posting. © American Geophysical Union, 2017. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Paleoceanography 32 (2017): 512–530, doi:10.1002/2016PA003072.

Description: The carbon isotope composition (δ13C) of seawater provides valuable insight on ocean circulation, air-sea exchange, the biological pump, and the global carbon cycle and is reflected by the δ13C of foraminifera tests. Here more than 1700 δ13C observations of the benthic foraminifera genus Cibicides from late Holocene sediments (δ13CCibnat) are compiled and compared with newly updated estimates of the natural (preindustrial) water column δ13C of dissolved inorganic carbon (δ13CDICnat) as part of the international Ocean Circulation and Carbon Cycling (OC3) project. Using selection criteria based on the spatial distance between samples, we find high correlation between δ13CCibnat and δ13CDICnat, confirming earlier work. Regression analyses indicate significant carbonate ion (−2.6 ± 0.4) × 10−3‰/(μmol kg−1) [CO32−] and pressure (−4.9 ± 1.7) × 10−5‰ m−1 (depth) effects, which we use to propose a new global calibration for predicting δ13CDICnat from δ13CCibnat. This calibration is shown to remove some systematic regional biases and decrease errors compared with the one-to-one relationship (δ13CDICnat = δ13CCibnat). However, these effects and the error reductions are relatively small, which suggests that most conclusions from previous studies using a one-to-one relationship remain robust. The remaining standard error of the regression is generally σ ≅ 0.25‰, with larger values found in the southeast Atlantic and Antarctic (σ ≅ 0.4‰) and for species other than Cibicides wuellerstorfi. Discussion of species effects and possible sources of the remaining errors may aid future attempts to improve the use of the benthic δ13C record.

Description: U.S. National Science Foundation Grant Numbers: 1634719, 0926735, 1125181; Swiss National Science Foundation Grant Numbers: PP00P2_144811, 200021_163003; Canadian Institute for Advanced Research (CIFAR); Canadian Foundation for Innovation (CFI); Natural Sciences and Engineering Research Council (NSERC)

Description: 2017-12-03

Description: © The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Newman, L., Heil, P., Trebilco, R., Katsumata, K., Constable, A., van Wijk, E., Assmann, K., Beja, J., Bricher, P., Colemans, R., Costa, D., Diggs, S., Farneti, R., Fawcett, S., Gille, S. T., Hendry, K. R., Henley, S., Hofmann, E., Maksym, T., MazIoff, M., Meijers, A., Meredith, M. M., Moreau, S., Ozsor, B., Robertson, R., Schloss, I., Schofield, O., Shi, J., Sikes, E., Smith, I. J., Swart, S., Wahlin, A., Williams, G., Williams, M. J. M., Herraiz-Borreguero, L., Kern, S., Liesers, J., Massom, R. A., Melbourne-Thomas, J., Miloslavich, P., & Spreen, G. Delivering sustained, coordinated, and integrated observations of the Southern Ocean for global impact. Frontiers in Marine Science, 6, (2019): 433, doi:10.3389/fmars.2019.00433.

Description: The Southern Ocean is disproportionately important in its effect on the Earth system, impacting climatic, biogeochemical, and ecological systems, which makes recent observed changes to this system cause for global concern. The enhanced understanding and improvements in predictive skill needed for understanding and projecting future states of the Southern Ocean require sustained observations. Over the last decade, the Southern Ocean Observing System (SOOS) has established networks for enhancing regional coordination and research community groups to advance development of observing system capabilities. These networks support delivery of the SOOS 20-year vision, which is to develop a circumpolar system that ensures time series of key variables, and delivers the greatest impact from data to all key end-users. Although the Southern Ocean remains one of the least-observed ocean regions, enhanced international coordination and advances in autonomous platforms have resulted in progress toward sustained observations of this region. Since 2009, the Southern Ocean community has deployed over 5700 observational platforms south of 40°S. Large-scale, multi-year or sustained, multidisciplinary efforts have been supported and are now delivering observations of essential variables at space and time scales that enable assessment of changes being observed in Southern Ocean systems. The improved observational coverage, however, is predominantly for the open ocean, encompasses the summer, consists of primarily physical oceanographic variables, and covers surface to 2000 m. Significant gaps remain in observations of the ice-impacted ocean, the sea ice, depths 〉2000 m, the air-ocean-ice interface, biogeochemical and biological variables, and for seasons other than summer. Addressing these data gaps in a sustained way requires parallel advances in coordination networks, cyberinfrastructure and data management tools, observational platform and sensor technology, two-way platform interrogation and data-transmission technologies, modeling frameworks, intercalibration experiments, and development of internationally agreed sampling standards and requirements of key variables. This paper presents a community statement on the major scientific and observational progress of the last decade, and importantly, an assessment of key priorities for the coming decade, toward achieving the SOOS vision and delivering essential data to all end-users.

Description: PH was supported by the Australian Government’s Cooperative Research Centers Program through the Antarctica Climate and Ecosystems Cooperative Research Centre, and the International Space Science Institute’s team grant #406. This work contributes to the Australian Antarctica Science projects 4301 and 4390.

Description: Author Posting. © American Geophysical Union, 2014. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Paleoceanography 29 (2014): 595–611, doi:10.1002/2013PA002584.

Description: This study examined sources of mixed layer and shallow subsurface waters in the subtropical Bay of Plenty, New Zealand, across the last deglaciation (~30–5 ka). δ18O and δ13C from planktonic foraminifera Globgerinoides bulloides and Globorotalia inflata in four sediment cores were used to reconstruct surface mixed layer thickness, δ18O of seawater (δ18OSW) and differentiate between high- and low-latitude water provenance. During the last glaciation, depleted planktonic δ18OSW and enriched δ13C (−0.4–0.1‰) indicate surface waters had Southern Ocean sources. A rapid δ13C depletion of ~1‰ in G. bulloides between 20 and 19 ka indicates an early, permanent shift in source to a more distal tropical component, likely with an equatorial Pacific contribution that persisted into the Holocene. At 18 ka, a smaller but similar shift in G. inflata δ13C depletion of ~0.3‰ suggests that deeper subsurface waters had a delayed reaction to changing conditions during the deglaciation. This contrasts with the isotopic records from nearby Hawke Bay, to the east of the North Island of New Zealand, which exhibited several changes in thermocline depth indicating switches between distal subtropical and proximal subantarctic influences during the early deglaciation ending only after the Antarctic Cold Reversal. Our results identify the midlatitude subtropics, such as the area around the North Island of New Zealand, as a key region to decipher high- versus low-latitude influences in Southern Hemisphere shallow water masses.

Description: Funding for this project came from NSF OCE-0823487 and 0823549-03.

Description: 2014-12-17

Description: 〈jats:p〉Abstract. We present a global atlas of downcore foraminiferal oxygen and carbon isotope ratios available at https://doi.org/10.1594/PANGAEA.936747 (Mulitza et al., 2021a). The database contains 2106 published and previously unpublished stable isotope downcore records with 361 949 stable isotope values of various planktic and benthic species of Foraminifera from 1265 sediment cores. Age constraints are provided by 6153 uncalibrated radiocarbon ages from 598 (47 %) of the cores. Each stable isotope and radiocarbon series is provided in a separate netCDF file containing fundamental metadata as attributes. The data set can be managed and explored with the free software tool PaleoDataView. The atlas will provide important data for paleoceanographic analyses and compilations, site surveys, or for teaching marine stratigraphy. The database can be updated with new records as they are generated, providing a live ongoing resource into the future. 〈/jats:p〉