Archives de catégorie : climate and geology

Constraining climate sensitivity and continental versus seafloor weathering using an inverse geological carbon cycle model

by J. Krissansen-Totton and D.C. Catling, May 22,  2017, in Nature


The relative influences of tectonics, continental weathering and seafloor weathering in controlling the geological carbon cycle are unknown. Here we develop a new carbon cycle model that explicitly captures the kinetics of seafloor weathering to investigate carbon fluxes and the evolution of atmospheric CO2 and ocean pH since 100 Myr ago.

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Porewater salinity reveals past lake-level changes in Lake Van, the Earth’s largest soda lake

by Yama Tomonaga et al., March 22, 2017, Nature


In closed-basin lakes, sediment porewater salinity can potentially be used as a conservative tracer to reconstruct past fluctuations in lake level. However, until now, porewater salinity profiles did not allow quantitative estimates of past lake-level changes because, in contrast to the oceans, significant salinity changes (e.g., local concentration minima and maxima) had never been observed in lacustrine sediments. Here we show that the salinity measured in the sediment pore water of Lake Van (Turkey) allows straightforward reconstruction of two major transgressions and a major regression that occurred during the last 250 ka.

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A paleo-perspective on ocean heat content: Lessons from the Holocene and Common Era

by Yair Rosenthal et al., January 1, 2017


 

Here we review proxy records of intermediate water temperatures from sediment cores in the equatorial Pacific and northeastern Atlantic Oceans, spanning 10,000 years beyond the instrumental record.

These records suggests that intermediate waters were 1.5–2 °C warmer during the Holocene Thermal Maximum than in the last century.

Intermediate water masses cooled by 0.9 °C from the Medieval Climate Anomaly to the Little Ice Age.

 

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Shelf sediments reveal climate shifts through the eons

by University of Queensland, May 10, 2017, in DailyScience


Ms Korpanty said global climate underwent significant change about 14 million years ago when the Antarctic ice sheet expanded.

« The new study presents shallow-marine sediment records from the Australian continental shelf, providing the first empirical evidence linking high-altitude cooling around Antarctica to climate change in the subtropics during the Miocene era, » she said.

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