| 1. |
- Tian, Ye, et al.
(författare)
-
Holocene climate change in southern Oman deciphered by speleothem records and climate model simulations
- 2023
-
Ingår i: Nature Communications. - 2041-1723. ; 14:1
-
Tidskriftsartikel (refereegranskat)abstract
- Qunf Cave oxygen isotope (& delta;O-18(c)) record from southern Oman is one of the most significant of few Holocene Indian summer monsoon cave records. However, the interpretation of the Qunf & delta;O-18(c) remains in dispute. Here we provide a multi-proxy record from Qunf Cave and climate model simulations to reconstruct the Holocene local and regional hydroclimate changes. The results indicate that besides the Indian summer monsoon, the North African summer monsoon also contributes water vapor to southern Oman during the early to middle Holocene. In principle, Qunf & delta;O-18(c) values reflect integrated oxygen-isotope fractionations over a broad moisture transport swath from moisture sources to the cave site, rather than local precipitation amount alone, and thus the Qunf & delta;O-18(c) record characterizes primary changes in the Afro-Asian monsoon regime across the Holocene. In contrast, local climate proxies appear to suggest an overall slightly increased or unchanged wetness over the Holocene at the cave site. Southern Oman speleothem oxygen isotope and multi-proxy data reveal diverse changes in the Afro-Indian summer monsoon circulations and local hydroclimate conditions during the Holocene, confirming climate model simulations.
|
|
| 2. |
- Gdaniec, Sandra, et al.
(författare)
-
A comparison of dissolved and particulate 231Pa, 230Th and 232Th concentrations measured at the GEOTRACES Arctic crossover station in 2015
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The global mapping of the GEOTRACES program requires consistent and precise measurements of 232Th (pg/kg), 230Th and 231Pa (fg/kg) in seawater and suspended particulate matter. Concentrations of particulate and dissolved 231Pa, 230Th and 232Th were measured by four labs in samples collected at the Arctic crossover station in 2015. These samples were collected during two separate expeditions (HLY1502 GN01, Station 30 and PS94 GN04 ARK-XXIX/3, Station 101). Detailed descriptions of chemical procedures used by the participating labs are followed by a discussion focused on dissolved surface samples and particulate samples. Results demonstrated that participating labs can determine concentrations of dissolved 230Th and 231Pa in deep water (<500 m depth) that are internally consistent within 4 % of the mean values. However, the analysis of radionuclide concentrations in suspended particles still needs improvement. The pre-concentration of particulate material used at LSCE was proven to be unsuccessful. Aliquots of particulate samples at St. 101 were re-measured and it was concluded that the absence of HF in the leaching solution was the cause for the previously underestimated particulate concentrations. Large blank contributions are still a problem, especially for measurements of particulate 231Pa.
|
|
