On March 01 at 16:00 UTC , Dr. Juan Muglia will be giving our first OC3 webinar: The OC3 deglacial stable isotope database: Features and tools
Abstract: The Ocean Carbon and Cycling Project (OC3) is an initiative to create a global database of deglacial benthic foraminifera stable isotope data from seafloor sediment cores. High resolution age models are included in the data base, with the aim to release a data product where stable isotope fields through the deglaciation could be analyzed in a “four dimensional” framework. In this talk we describe the current state of the data base, show some analyzing tools for users, and discuss future applications and goals.
Dr. Janne Repschläger will be giving our 2nd OC3 webinar at 15:00 UTC, Apr 05. The title of her talk is: Insights into deglacial AMOC changes - a summary of the PAGES OC3 stable isotope compilation data from the North Atlantic
Abstract:
The Atlantic Meridional Overturning Circulation (AMOC) during the last glacial interval was considerably different from modern ocean circulation, including changes in deepwater formation, position of convection sites, depth of overturning, deepwater flow strength and stratification. Deepwater circulation significantly changed during the last deglaciation from a shallow to a deep-reaching overturning cell. This change went along with a drawdown of isotopically light waters into the abyss and a deep ocean warming that changed deep ocean stratification from a salinity- to a temperature-controlled mode. Yet, the exact mechanisms causing these changes are still unknown. Furthermore, the long-standing ideas of a northward extension of Southern Ocean water during the Last Glacial Maximum (LGM) and a complete shutdown of North Atlantic deepwater formation during Heinrich Stadial 1 (HS1) (17.5-14.6 kyr BP) remains prevalent.
For a better understanding of the glacial and deglacial deepwater circulation changes, a compilation of published and unpublished benthic δ13C and δ18O data is established within the framework of the PAGES OC3 working group. Here, we present the extensive compilation data from the North Atlantic Ocean with 105 sediment cores. The combined benthic δ13C and δ18O indicate the existence of a 13C-depleted and 18O-enriched North Atlantic deepwater mass traceable at depths between 4000 and 3000 m and between 50 and 20°N during the Last Glacial Maximum and into Heinrich Stadial 1 (HS1). Benthic 14C ages in the deep North Atlantic younger than the Southern Ocean and a barrier of 13C-enriched and 18O-depleted water in the deep equatorial Atlantic exclude a southern origin of this water mass. Instead, transects across the subpolar and polar North Atlantic point toward an active deepwater formation in the Irminger Sea and/or Labrador Sea region. During HS1 a δ18O-depleted, δ13C-enriched, young water mass is apparent at latitudes between 40 and 50°N in the western North Atlantic Basin that reached a depth of 4000 m. The abrupt occurrence of the δ18O depleted signature in the western Atlantic Basin indicate either two different deepwater sources during HS1 or an alteration of the deepwater on its southward pathway. Based on these results, we discuss concepts of deepwater formation in the North Atlantic that help to explain the deglacial change from a salinity-driven to a temperature-driven circulation mode from the LGM to the Late Holocene.
Dr. Stefan Mulitza from MARUM, Germany will be giving our 3rd OC3 webinar at 15:00 UTC, May 10. The title of his talk is: Harmonizing foraminiferal proxy data: implications for deglacial changes in global mean sea surface temperature and ocean circulation.
Abstract:
As paleoclimate data are the only means to evaluate climate models beyond the instrumental phase and on longer (i.e., centennial and millennial) timescales, the comparison of climate model output and paleoclimatic data will remain a central task for current and future generations of climate scientists. Although foraminiferal proxy data are available in vast quantities and often with global coverage, only very few quality-controlled proxy data compilations have been published so far, mainly due to inconsistencies in the applied stratigraphic methods, inhomogeneous data structures and often highly fragmented data sets. To improve the efficiency and sustainability of the compilation process, we have created the desktop applications PaleoDataView and PaleoDataMap. I will show how these software-toolboxes can be applied to data collections of foraminiferal d18O, d13C and Mg/Ca produced within the PAGES OC3 and PalMod projects and discuss the implications for the evolution of global mean sea surface temperature and ocean circulation over the last deglaciation.
Prof. Lorraine Lisiecki from University of California, Santa Barbara will be the speaker for our next OC3 webinar (15:00 UTC, July 19). The title of her talk is A Bayesian Multiproxy Approach to Regional Age Models.
Abstract:
Previously developed software packages that generate probabilistic age models for sediment cores are designed to use either age proxies (e.g., radiocarbon or tephra layers) or stratigraphic alignment (e.g., of benthic δ18O) and cannot combine age inferences from both techniques. Furthermore, many radiocarbon dating packages are not specifically designed for marine sediment cores and default settings may not accurately reflect sedimentation rate variability in the deep ocean, requiring subjective tuning of parameter settings. Here we present a new technique for generating Bayesian age models and stacks of ocean sediment core data, implemented in a software package named BIGMACS (Bayesian Inference Gaussian Process regression and Multiproxy Alignment of Continuous Signals). BIGMACS constructs multiproxy age models by combining age inferences from both radiocarbon ages and δ18O stratigraphic alignment and constrains sedimentation rates using an empirically derived prior model based on 37 14C-dated ocean sediment cores (Lin et al., 2014). BIGMACS also constructs continuous benthic δ18O stacks via a Gaussian process regression, which requires a smaller number of cores than previous stacking methods. This feature allows users to construct stacks for a small hydrographic region that shares a homogeneous deep water δ18O signal, while leveraging radiocarbon dates across multiple cores. Thus, BIGMACS efficiently generates local or regional stacks with smaller uncertainties in both age and δ18O than previously available techniques.