@article {2751, title = {Large-Scale Intrusion of Circumpolar Deep Water on Antarctic Margin Recorded by Stylasterid Corals}, journal = {Paleoceanography and Paleoclimatology}, volume = {33}, year = {2018}, month = {May-11-2018}, pages = {1306 - 1321}, abstract = {We present centennial-scale radiocarbon (14C) records archived by deep sea stylasterid corals from the outer shelf and upper slope of the Antarctic margin. These novel stylasterids (Errina spp.) were collected from the western Ross Sea shelf (500 m) and slope (1,700 m), as well as the eastern Wilkes Land shelf (670 m). We provide two corals from each region and document an abrupt reversal of 14C ages in the upper (younger) part of each coral. We test the statistical robustness of each record and demonstrate the significance of the age reversals, as well as the ability of these corals to record environmental change. We discuss a variety of possible drivers for this 14C reversal and conclude that it is most likely an encroachment of 14C-depeleted Circumpolar Deep Water (CDW). This water mass has regionally intruded onto the Antarctic margin in recent decades, facilitating loss of grounded Antarctic ice; which has implications for global sea level, deep-water formation, and carbon sequestration in the Southern Ocean. Thus, understanding the past variability of CDW on the margin is vital to better constrain climate change trajectories in the near future. We estimate large-scale encroachment of CDW onto the shelf likely commencing after 1830 CE ({\textpm}120 year). We present possible drivers for the intrusion, but highlight the need for additional chronologic constraint. This study not only demonstrates the utility of a novel coral taxon but also presents the paleoceanographic community with a testable hypothesis concerning a recent, widespread CDW intrusion.}, issn = {2572-4517}, doi = {10.1029/2018PA003439}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1029/2018PA003439}, author = {King, Theresa M. and Rosenheim, Brad E. and Post, Alexandra L. and Gabris, Theresa and Burt, Taylor and Domack, Eugene W.} } @article {2752, title = {Mangrove sediment carbon stocks along an elevation gradient: Influence of the late Holocene marine regression (New Caledonia)}, journal = {Marine Geology}, volume = {404}, year = {2018}, month = {Jan-10-2018}, pages = {60 - 70}, abstract = {Among blue carbon ecosystems, mangroves are very efficient in storing carbon in their sediments over decadal to millennial time scales. However, this ability varies with numerous parameters, including climate and sea-level variations. In New Caledonia, mangrove ecosystems develop in semi-arid conditions with a typical zonation: Rhizophora spp. colonize the seaward side of the intertidal area, while Avicennia marina develops at higher elevations, just below the salt-flat. Within this context, we determined both the quantity (organic carbon content and carbon stocks) and the characteristics (carbon over nitrogen ratios (C/N), stable carbon and nitrogen isotopes, radiocarbon age) of the organic matter stored beneath each mangrove stands. Carbon stocks were determined down to different limits with depth: approximate extension of the root systems, one-meter depth, and the hard substrate. Within the extension of the root systems, the sediment carbon stock was lower than 100 MgC ha-1 regardless of the mangrove species. This low value resulted directly from the dry climate that limits mangrove productivity. At depth beneath every zone, a buried layer enriched in mangrove-derived organic matter, with C/N values around 40 and δ13C values around -26{\textperthousand} was observed. This layer likely resulted from a sea-level high stand during the late Holocene that allowed a long period of stability of the mangrove, slowly accumulating organic matter within the sediment. In this buried layer, the carbon stock was higher than in the upper sediment and reached up to 665, 255 and 300 MgC ha-1 in the salt-flat zone, the A. marina stand and the R. spp. stand, respectively. The highest stock, determined beneath the salt-flat, was suggested to be related to a period of sea-level stability that lasted ~3000 years, whereas beneath the other zones, which are at lower elevations, mangrove colonization was more recent and the sea-level was continuously decreasing till recently. Sea-level variations, and, specifically current sea-level rise, may strongly influence mangrove development due to their migration along the tidal elevation gradient to maintain the biotic conditions needed for their development.}, keywords = {Blue carbon, carbon isotopes, carbon sequestration, Coastal wetlands, Sea-level change, Semi-arid mangrove forest}, issn = {00253227}, doi = {10.1016/j.margeo.2018.07.005}, url = {https://linkinghub.elsevier.com/retrieve/pii/S0025322717306072}, author = {Jacotot, Adrien and Marchand, Cyril and Rosenheim, Brad E. and Domack, Eugene W. and Allenbach, Michel} } @article { ISI:000352212200018, title = {Late Holocene glacial advance and ice shelf growth in Barilari Bay, Graham Land, west Antarctic Peninsula}, journal = {GEOLOGICAL SOCIETY OF AMERICA BULLETIN}, volume = {127}, number = {{1-2}}, year = {2015}, month = {JAN-FEB}, pages = {297-315}, type = {Article}, abstract = {Three marine sediment cores were collected along the length of the fjord axis of Barilari Bay, Graham Land, west Antarctic Peninsula (65 degrees 55{\textquoteright}S, 64 degrees 43{\textquoteright}W). Multi-proxy analytical results constrained by high-resolution geochronological methods (Pb-210, radiocarbon, Cs-137) in concert with historical observations capture a record of Holocene paleoenvironmental variability. Our results suggest early and middle Holocene (>7022-2815 cal. {[}calibrated] yr B.P.) retreated glacial positions and seasonally open marine conditions with increased primary productivity. Climatic cooling increased sea ice coverage and decreased primary productivity during the Neoglacial (2815 to cal. 730 cal. yr B.P.). This climatic cooling culminated with glacial advance to maximum Holocene positions and expansion of a fjord-wide ice shelf during the Little Ice Age (LIA) (ca. 730-82 cal. yr B.P.). Seasonally open marine conditions were achieved and remnant ice shelves decayed within the context of recent rapid regional warming (82 cal. yr B.P. to present). Our findings agree with previously observed late Holocene cooling and glacial advance across the Antarctic Peninsula, suggesting that the LIA was a regionally significant event with few disparities in timing and magnitude. Comparison of the LIA Antarctic Peninsula record to the rest of the Southern Hemisphere demonstrates close synchronicity in the southeast Pacific and southern most Atlantic region but less coherence for the southwest Pacific and Indian Oceans. Comparisons with the Northern Hemisphere demonstrate that the LIA Antarctic Peninsula record was contemporaneous with pre-LIA cooling and sea ice expansion in the North Atlantic-Arctic, suggesting a global reach for these events.}, issn = {0016-7606}, doi = {10.1130/B31035.1}, author = {Christ, Andrew J. and Talaia-Murray, Manique and Elking, Natalie and Domack, Eugene W. and Leventer, Amy and Lavoie, Caroline and Brachfeld, Stefanie and Yoo, Kyu-Cheul and Gilbert, Robert and Jeong, Sun-Mi and Petrushak, Stephen and Wellner, Julia and LARISSA Grp} }