28 Sep 2023
 | 28 Sep 2023
Status: this preprint is open for discussion and under review for Climate of the Past (CP).

Stable isotope evidence for long-term stability of large-scale hydroclimate in the Neogene North American Great Plains

Livia Manser, Tyler Kukla, and Jeremy K. C. Rugenstein

Abstract. The Great Plains of North America host a stark climatic gradient, separating the humid and well-watered eastern US from the semi-arid and arid western US. First studied in detail by John Wesley Powell, this gradient shapes the region’s ecosystems, economies, and the availability of water across the landscape. This gradient is largely set by the influence of two competing atmospheric circulation systems that meet over the Great Plains – the wintertime westerlies bring dominantly dry air that gives way to moist, southerly air transported by the Great Plains Low-Level Jet in the warmer months. Climate model simulations suggest that, as CO2 rises, this low-level jet will strengthen, leading to greater precipitation in the spring, but less in the summer and, thus, no change in mean annual precipitation. Combined with rising temperatures that will increase potential evapotranspiration, semi-arid conditions will shift eastward, with potentially large consequences for the ecosystems and inhabitants of the Great Plains. We examine how hydroclimate in the Great Plains varied in the past in response to warmer global climate by studying the paleoclimate record within the Ogallala Formation, which underlies nearly the entire Great Plains and provides a spatially resolved record of hydroclimate during the globally warmer late Miocene. We use the stable isotopes of oxygen (δ18O) as preserved in authigenic carbonates hosted within the abundant paleosol and fluvial successions that comprise the Ogallala Formation as a record of past hydroclimate. Today, and coincident with the modern aridity gradient, there is a sharp meteoric water δ18O gradient with high (−6 to 0 ‰) δ18O in the southern Great Plains and low (−12 to −18 ‰) δ18O in the northern Plains. We find that the spatial pattern of reconstructed late Miocene precipitation δ18O is indistinguishable from the spatial pattern of modern meteoric water δ18O. We use a recently developed vapor transport model to demonstrate that this δ18O spatial pattern requires air mass mixing over the Great Plains between dry westerly and moist southerly air masses in the late Miocene – consistent with today. Our results suggest that the spatial extent of these two atmospheric circulation systems have been largely unchanged since the late Miocene and any strengthening of the Great Plains Low-Level Jet in response to warming has been isotopically masked by proportional increases in westerly moisture delivery. Our results hold implications for the sensitivity of Great Plains climate to changes in global temperature and CO2 and also for our understanding of the processes that drove Ogallala Formation deposition in the late Miocene.

Livia Manser et al.

Status: open (extended)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-2075', Anonymous Referee #1, 01 Nov 2023 reply

Livia Manser et al.

Livia Manser et al.


Total article views: 227 (including HTML, PDF, and XML)
HTML PDF XML Total BibTeX EndNote
155 63 9 227 4 5
  • HTML: 155
  • PDF: 63
  • XML: 9
  • Total: 227
  • BibTeX: 4
  • EndNote: 5
Views and downloads (calculated since 28 Sep 2023)
Cumulative views and downloads (calculated since 28 Sep 2023)

Viewed (geographical distribution)

Total article views: 225 (including HTML, PDF, and XML) Thereof 225 with geography defined and 0 with unknown origin.
Country # Views %
  • 1
Latest update: 29 Nov 2023
Short summary
The Great Plains host the single most important climatic boundary in North America, separating the humid east from the semi-arid west. How this boundary will move as the world warms holds implications for the societies and ecosystems of the Plains. We study how this boundary changed in the past during a period of globally warmer temperatures. We find that this climatic boundary appears to be in the same location as today, suggesting that Great Plains climate is resilient to global changes.