The atmospheric bridge communicated the δ13C decline during the last deglaciation to the global upper ocean

During the early part of the last glacial termination (17.2-15 ka) and coincident with a ∼ 35 ppm rise in atmospheric CO2, a sharp 0.3‰-0.4‰ decline in atmospheric δ13CO2 occurred, potentially constraining the key processes that account for the early deglacial CO2 rise. A comparable δ13C decline has also been documented in numerous marine proxy records from surface and thermocline-dwelling planktic foraminifera. The δ13C decline recorded in planktic foraminifera has previously been attributed to the release of respired carbon from the deep ocean that was subsequently transported within the upper ocean to sites where the signal was recorded (and then ultimately transferred to the atmosphere). Benthic δ13C records from the global upper ocean, including a new record presented here from the tropical Pacific, also document this distinct early deglacial δ13C decline. Here we present modeling evidence to show that rather than respired carbon from the deep ocean propagating directly to the upper ocean prior to reaching the atmosphere, the carbon would have first upwelled to the surface in the Southern Ocean where it would have entered the atmosphere. In this way the transmission of isotopically light carbon to the global upper ocean was analogous to the ongoing ocean invasion of fossil fuel CO2. The model results suggest that thermocline waters throughout the ocean and 500-2000m water depths were affected by this atmospheric bridge during the early deglaciation

Sea surface temperature changes in the southern California borderlands during the last glacial-interglacial cycle

A variety of evidence suggests that average sea surface temperatures (SSTs) during the last glacial maximum in the California Borderlands region were significantly colder than during the Holocene. Planktonic foraminiferal δ18O evidence and average SST estimates derived by the modern analog technique indicate that temperatures were 6°-10°C cooler during the last glacial relative to the present. The glacial plankton assemblage is dominated by the planktonic foraminifer Neogloboquadrina pachyderma (sinistral coiling) and the coccolith Coccolithus pelagicus, both of which are currently restricted to subpolar regions of the North Pacific. The glacial-interglacial average SST change determined in this study is considerably larger than the 2°C change estimated by Climate: Long-Range Investigation, Mapping, and Prediction (CLIMAP) [1981]. We propose that a strengthened California Current flow was associated with the advance of subpolar surface waters into the Borderlands region during the last glacial

Assessing the stratigraphic integrity of planktic and benthic 14 c records in the western pacific for δ 14 c reconstructions at the last glacial termination

There is a growing database of radiocarbon (14C) reconstructions from biogenic carbonate taken from marine sediment cores being used to investigate changing ocean circulation and carbon cycling at the end of the last great ice age. Reported here are 14C results from a marine core taken in the Makassar Straits of the western equatorial Pacific that was intended to test whether there was evidence of geologic carbon release to the ocean during the glacial termination. A thorough investigation of planktic and benthic 14C ages with stable isotopes and CT-scans revealed extensive burrowing in the upper 2 m of the core that displaced younger sediments downward by more than half a meter into the glacial section of the core. The vertical displacement is evident in both planktic and benthic fossils. However, the extent of displacement and the stratigraphic disturbance became evident only after multiple measurements of different species and genera. A CT-scan prior to sampling would be an effective screening tool to avoid sampling problem cores such as this

Antarctic Paleogene planktonic foraminifera

ODP Leg 113 drilled the first nearly continuous pre-Neogene calcareous biogenic sequence from the Antarctic Ocean at Sites 689 and 690. At 65∞S, these are probably the highest latitude calcareous sequences available in the Southern Hemisphere deep oceans. Together these two sites provide a nearly complete planktonic foraminifer history for the Late Cretaceous through late Oligocene. Planktonic foraminifers are abundant and generally well preserved from the Upper Cretaceous to the Eocene. Abundances and the quality of preservation are reduced during the Oligocene as calcareous microfossil groups are progressively replaced by siliceous groups. The Neogene is marked by only rare, isolated occurrences of planktonic foraminifers, the most conspicuous of which are of Quaternary age. The diversity of planktonic foraminifers was low following the mass extinction event at the Cretaceous/Paleogene boundary. The lowermost Paleogene fossil assemblages following the mass extinction event closely resemble those of lower latitudes. During the middle Paleocene, a "high latitude" assemblage developed that lacked species found at lower latitudes, particularly the early morozovellids. The diversity increased during the late Paleocene through evolutionary radiation in conjunction with warm conditions at high latitudes. Diversity remained high in the Antarctic throughout most of the early and early middle Eocene. Subbotinids and acarininids dominated the assemblages along with various Planorotalites species. At no time, however, did any of the large-keeled morozovellids, the hantkeninids, or the globigerapsids characteristic of the low latitudes inhabit the Antarctic Ocean. Beginning in the late middle Eocene, planktonic foraminifer diversity was reduced due to the extinction of the acarininids and several Subbotina and Planorotalites species. In the upper Eocene the fossil assemblages exhibit even lower diversity and are dominated by three to four species. These changes correspond to the beginning of a long-term climatic cooling trend that is also recorded in the stable isotopic records. Further reduction in diversity occurred across the Eocene/Oligocene boundary in response to continued cooling and increased CaCO3 dissolution. At that time siliceous microfossils began to appear in increasing abundance. A new planktonic foraminifer biostratigraphy has been developed for the Weddell Sea area, Antarctica. Fourteen biozones are defined on the basis of distinct biohorizons used to mark the top and bottom of each zone, and are intercalibrated with magnetostratigraphy. This stratigraphy has been correlated with the well-established low-latitude zonations