Radiocarbon dating of alkenones from marine sediments free real adult chat
Surface hydrographic changes in the OT have been reconstructed based on various proxies.
Past sea surface temperatures (SSTs) in the OT have been reconstructed from various proxies, including alkenone, planktonic foraminiferal Mg/Ca, planktonic foraminiferal assemblages, and glycerol dibiphytanyl glycerol tetraether (GDGT) (Jian et al. These suggest that changes in the main axis and volume transport of the KC and the intensity of the East Asian summer monsoon affected the surface changes in the OT.
As the reconstruction of past SSTs from alkenone, Mg/Ca, and GDGT is based on the information recorded in marine organisms such as coccolithophores, foraminifera, and , knowledge on the habitat depth and seasonal abundance of these organisms is relevant.
It is essential to accurately determine what depth and season are represented by the temperatures estimated using these proxies.
In core A7, however, a reservoir age of 700 y was used because the converted calendar ages were in good agreement with the K-Ah tephra age (Sun et al. Temperatures for the alkenone proxy are the annual mean temperatures at depths of 0–30 m; those for the Mg/Ca proxy are June–November mean temperatures at depths of 0–50 m; and those for the summer and winter assemblage-based temperatures are August and February temperatures at 0 m, respectively ).
In Section 5, we review glacial–interglacial changes in the surface hydrography of the OT and their paleoclimatological implications.).
Ash layers, including the Kikai-Akahoya (K-Ah) and the Aira-Tanzawa (AT), were found in cores DGKS9603 and MD98-2195.
In addition, the proxy temperature estimates from core-top sediments are compared with observed SSTs to confirm that proxy temperatures reconstructed from marine sediments can represent the current SST in the OT.
In Section 4, we compare SST proxy data for the late Holocene (0–3 cal ky BP) and the last glacial maximum (LGM, 18–21 cal ky BP).