[1] Carbon (C) and nitrogen (N) concentrations and isotopic compositions were determined for sediments from Ocean Drilling Program legs 170 and 205 offshore of Costa Rica, in an attempt to characterize C-N flux into the Central America (CA) convergent margin and identify signatures of diagenesis and changing productivity in this sediment section. Samples from sites 1039 and 1253 (outboard of the trench) contain 62 to 2382 ppm total nitrogen (TN) with d 15 N Air values of +2.4 to +8.5%, 0.04-2.65 wt% total organic carbon (TOC) with d 13 C VPDB values of À25.4 to À20.8%, and 1.1-87.3 wt% carbonate with d 13 C values of +0.1 to +3.2% and d 18 O VSMOW values of +21.3 to +34.2%. Total organic C and TN concentrations strongly depend on lithology, with carbonate-rich samples containing smaller amounts of both. Total organic C and TN concentrations and isotopic compositions also vary systematically within single units, perhaps reflecting small degrees of diagenetic alteration but mostly significant increase in productivity since the early Pliocene. Sediment subduction feeds 1.3 Â 10 10 g yr À1 N (mean d 15 N = +5.7%), 1.4 Â 10 11 g yr À1 TOC (mean d 13 C = À22.0%) and 1.5 Â 10 12 g yr À1 oxidized C (mean d 13 C = +1.9%) into the 1100 km CA convergent margin. Incorporating possible inputs in altered oceanic crust (AOC) and by tectonic erosion, the C-N inputs appear to be far larger than the arc outputs. A small part of this excess C and N is probably returning toward the surface by devolatilization, along structural heterogeneities in the forearc, and the remaining inventory is likely recycling into the deeper mantle.Citation: Li, L., and G. E. Bebout (2005), Carbon and nitrogen geochemistry of sediments in the Central American convergent margin: Insights regarding subduction input fluxes, diagenesis, and paleoproductivity,

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The paucity of high‐resolution paleoclimate records limits our ability to extend instrumental data into a longer time‐frame and to better understand multidecadal climate variations in the Mid‐Atlantic region. Here we present an ∼2 year‐resolution endogenic calcite δ18O record for the last ∼240 years from a freeze core at White Lake in northern New Jersey. The δ18O data, consistent with the paleosalinity reconstructions from Chesapeake Bay, suggest regional‐scale multidecadal moisture variations, including dry conditions at 1780–1840, wet conditions at 1840–1920, and ∼20 year moisture oscillations after 1920. We attribute these moisture changes to shifts in the extent and location of the jet stream and resultant change in storm track trajectories, with eastward and seaward displacement of storm tracks corresponding to dry climate. The increase in moisture variability since 1920, shortly after the steady increase in global air temperature, suggests that change in mean climate state can induce large changes in moisture variability.