Limited freshwater cap in the Eocene Arctic Ocean
| Autor: | Stephen E. Grasby, David H. McNeil, Lisa A. Neville |
|---|---|
| Rok vydání: | 2019 |
| Předmět: |
0301 basic medicine
geography Multidisciplinary geography.geographical_feature_category biology lcsh:R Ocean current lcsh:Medicine Azolla event Structural basin Azolla biology.organism_classification Article Continental fragment 03 medical and health sciences 030104 developmental biology 0302 clinical medicine Oceanography Arctic Ridge lcsh:Q Water cycle lcsh:Science 030217 neurology & neurosurgery Geology |
| Zdroj: | Scientific Reports, Vol 9, Iss 1, Pp 1-6 (2019) Scientific Reports |
| ISSN: | 2045-2322 |
| DOI: | 10.1038/s41598-019-40591-w |
| Popis: | Remains of the freshwater fern Azolla, found in Eocene (~50 Ma ago) sediments in the modern central Arctic Ocean, have been used to suggest that seasonal freshwater caps covered the entire Arctic Ocean during that time, with significant impact on global ocean circulation and climate. However, these records are located on the Lomonosov Ridge, which during the Eocene was a continental fragment barely rifted from Eurasia, separating the smaller Eurasian Basin from the much larger Amerasian Basin to the west. As such, the Lomonosov Ridge does not necessarily record environmental conditions of the broader Arctic Ocean. We tested the hypothesis of freshwater caps by examining sediment records from the western Amerasian Basin. Here we show that in the larger Amerasian Basin the Azolla event is associated with marine microfauna along with allochthonous (terrestrially sourced) organic matter. We propose that Azolla events are related to an increased hydrologic cycle washing terrestrially sourced Azolla, and other organics, into the Arctic Ocean. If freshwater caps did occur, then they were at best restricted to the small Eurasian Basin and would have had a limited impact on Eocene global climate, contrary to current models. |
| Databáze: | OpenAIRE |
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