Radiocarbon measurements of hermatypic corals from 4 sites in the Gulf of Mexico (GOM) and Caribbean Sea were made to estimate the marine 14C reservoir age (R) and the marine regional correction (ΔR) for this region. Coral skeletal material from the Flower Garden Banks (northern GOM continental shelf), Veracruz, Mexico, and 2 reefs from the Cariaco Basin, Venezuela, were analyzed. Annual and subannual samples from 1945–1955 were milled and 14C composition was determined. In the Gulf of Mexico, average coral Δ14C is −52.6 ± 0.7‰ and average Δ14C for the Cariaco Basin corals is −53.4 ± 0.8‰. Average values for the marine reservoir age and ΔR are computed with this data and compared with results derived from previous measurements made in the same regions. These values are important in calibrating the 14C ages of carbonate samples from the area.

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[1] The thermometer-based global surface temperature time series (GST) commands a prominent role in the evidence for global warming, yet this record has considerable uncertainty. An independent record with better geographic coverage would be valuable in understanding recent change in the context of natural variability. We compiled the Paleo Index (PI) from 173 temperature-sensitive proxy time series (corals, ice cores, speleothems, lake and ocean sediments, historical documents). Each series was normalized to produce index values of change relative to a 1901-2000 base period; the index values were then averaged. From 1880 to 1995, the index trends significantly upward, similar to the GST. Smaller-scale aspects of the GST including two warming trends and a warm interval during the 1940s are also observed in the PI. The PI extends to 1730 with 67 records. The upward trend appears to begin in the early 19th century but the year-to-year variability is large and the 1730-1929 trend is small. Citation:

The 8.2 ka event is a key test case for simulating the coupled climate response to changes in the Atlantic Meridional Overturning Circulation (AMOC). Recent advances in quantifying freshwater fluxes at 8.2 ka from the proxy record have improved the realism of the forcing magnitude in model simulations, yet this forcing is still generally applied in an unrealistic geographic manner, across most of the Labrador Sea rather than just along the Labrador coast. Previous simulations with eddy-resolving ocean models have come to conflicting conclusions regarding the ability of such a coastally confined flow to impact the AMOC. These simulations have also not incorporated full atmosphere models nor have they used the new meltwater forcing values for 8.2 ka. We use the Community Climate System Model, version 3, with an ocean model resolution only slightly coarser than that used in previous eddy-resolving simulations, to test the sensitivity to freshwater forcing location. When revised freshwater forcing is applied across the Labrador Sea, the AMOC is reduced bỹ 40% and climate anomalies compare well with proxy records of the 8.2 ka event in terms of magnitude and duration. When the forcing is added just along the Labrador coast, however, most meltwater joins the subtropical gyre and travels to the subtropics with minor impact to the AMOC (~10% decrease). It is likely that model biases in the placement of the North Atlantic Current remain an important limitation for correctly simulating the 8.2 ka event.

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Continental shelf environments are uniquely situated to capture some of the most dynamic processes on Earth including climatic variability and anthropogenic modifications to coastal systems. Understanding how these processes have affected sediment delivery and accumulation on the shelf in the past may provide insight into potential changes in the future. To address this, we investigated shelf sedimentation within Monterey Bay, California. Sediment cores were collected from four locations throughout the bay to capture both the modern and late Holocene sedimentological record using grain size analysis, and sediment chronologies determined from 210 Pb, 137 Cs, and 14 C. From the grain size results we focused on the total percent sand,