Identifying processes within the Earth System that have modulated atmospheric pCO2 during each glacial cycle of the late Pleistocene stands as one of the grand challenges in climate science. The growing array of surface ocean pH estimates from the boron isotope proxy across the last glacial termination may reveal regions of the ocean that influenced the timing and magnitude of pCO2 rise. Here we present two new boron isotope records from the subtropical‐subpolar transition zone of the Southwest Pacific that span the last 20 kyr, as well as new radiocarbon data from the same cores. The new data suggest this region was a source of carbon to the atmosphere rather than a moderate sink as it is today. Significantly higher outgassing is observed between ~16.5 and 14 kyr BP, associated with increasing δ13C and [CO3]2− at depth, suggesting loss of carbon from the intermediate ocean to the atmosphere. We use these new boron isotope records together with existing records to build a composite pH/pCO2 curve for the surface oceans. The pH disequilibrium/CO2 outgassing was widespread throughout the last deglaciation, likely explained by upwelling of CO2 from the deep/intermediate ocean. During the Holocene, a smaller outgassing peak is observed at a time of relatively stable atmospheric CO2, which may be explained by regrowth of the terrestrial biosphere countering ocean CO2 release. Our stack is likely biased toward upwelling/CO2 source regions. Nevertheless, the composite pCO2 curve provides robust evidence that various parts of the ocean were releasing CO2 to the atmosphere over the last 25 kyr.

Pockmarks overlie subsurface deformation features indicative of over-pressurized vertical fluid flow  Negative Δ 14 C anomalies occur in sediments deposited near pockmarks at the glacial termination indicate 14 C-dead carbon was released from subducted carbonates.

a b s t r a c tA total of 220 surface sediments and eight sediment cores were analyzed to study the distribution and transport of Hg in Chinese marginal seas. Spatial distribution showed a general offshore decreasing trend towards the outer continental shelf. Vertical profiles of sediment cores displayed a general increasing trend from bottom to surface layers. Coastal land-based discharges and river-derived inputs are probably the main sources of Hg in coastal sediments of China seas, while TOC, pH, ocean currents and sediment characteristics could play important roles in the transport and spatial distribution of Hg in sediment. The influence of TOC on Hg concentration is more significant than that of pH. The mud deposits on the coastal shelves are main sinks of Hg in the region. The results showed that sedimentary Hg was affected by regional anthropogenic activities and riverine runoffs, and was also influenced by long-range atmospheric transport and ocean current circulations.