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Abstract Peak Neogene warmth and minimal polar ice volumes occurred during the Miocene Climatic Optimum (MCO, ca. 16.95–13.95 Ma) followed by cooling and ice sheet expansion during the Middle Miocene Climate Transition (MMCT, ca. 13.95–12.8 Ma). Previous records of northern high-latitude sea surface temperatures (SSTs) during these global climatic transitions are limited to Atlantic sites, and none resolve orbital-scale variability. Here, we present an orbital-resolution alkenone SST proxy record from the subpolar North Pacific that establishes a local maximum of SSTs during the MCO as much as 16 °C warmer than modern with rapid warming initiating the MCO, cooling synchronous with Antarctic ice sheet expansion during the MMCT, and high variability on orbital time scales. Persistently cooler North Pacific SST anomalies than in the Atlantic at equivalent latitudes throughout the Miocene suggest enhanced Atlantic northward heat transport under a globally warm climate. We conclude that a global forcing mechanism, likely elevated greenhouse gas concentrations, is the most parsimonious explanation for synchronous global high-latitude warmth during the Miocene.
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Increased moisture availability in the Central Andes during the Miocene Climatic Optimum
The Miocene Climatic Optimum (MCO; ~17–14 Ma) is one of Earth’s most recent protracted warming events and serves as an analog to anthropogenic climate change. Constraining the land surface response to the MCO is critical for paleoclimate model validation and for predictions of future climatic response. However, nonmarine records across the MCO interval are limited. The hinterland and foreland basins of the southern Central Andes in Argentina preserve stratigraphic records across the MCO. These continental deposits record the onset of dune fields at >30 Ma to ~19 Ma, with widespread eolian deposition at ~22–17 Ma. We document a regional change from eolian dune fields to fluvial and lacustrine conditions at ~18–15 Ma, broadly coincident with the MCO, over ~1000 km along-strike, in localities that would have occupied both high and low elevation positions and from different tectono-morphic settings. These paleoenvironmental changes are corroborated by new climate model simulations which show increased seasonality and precipitation along the eastern flank of the southern Central Andes during the MCO. Our results support a shift from arid to more humid and seasonal conditions during the MCO in the southern Central Andes, likely driven by intensification of the South American monsoon
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- PAR ID:
- 10584594
- Publisher / Repository:
- Elsevier
- Date Published:
- Journal Name:
- Palaeogeography, Palaeoclimatology, Palaeoecology
- Volume:
- 663
- Issue:
- C
- ISSN:
- 0031-0182
- Page Range / eLocation ID:
- 112732
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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