New Mexico Geological Society Annual Spring Meeting — Abstracts

The climatic evolution of New Mexico and the SW United States from the Late Permian to recent is simulated using the GENESIS climate model. The purpose is to evaluate predictions of climatic change through geologic time by comparing a series of climate model predictions with paleoclimates reconstructed from the sedimentary record of this region.

New Mexico has experienced substantial changes in paleogeography over the Late Permian to recent timespan including changes in both paleolatitude and relative position to other landmasses, as well as in its topographic evolution. Carbon-cycle geochemical models, supported by limited geochemical proxy data, indicate that atmospheric carbon dioxide levels have varied through time from present/glacial levels to as much as 6 to 8 times present values in the mid-Cretaceous.

Climate model simulations were carried out for 12 time slices spaced at roughly 20 million year intervals between the Late Permian and recent which address these changes in geography and atmospheric carbon dioxide levels. The model results predict large and well-defined changes in climate which can be compared to the geologic record.

In the Late Permian, New Mexico was located in the interior of the supercontinent Pangea and experienced very hot and dry conditions with some summer monsoonal rainfall. Average winter temperatures are predicted to have been above 20°C and average summer temperatures above 30°c. As Pangea separated into smaller landmasses in the late Jurassic, temperatures became less extreme and a more humid climate developed. By the mid-Cretaceous, the climate of NM is predicted to have been warm temperature to humid subtropical. Relatively high annual precipitation rates are predicted with an even distribution of rain between summer and winter. In the Tertiary, NM temperatures are predicted to cool relative to the Cretaceous as North America drifts slightly north and atmospheric carbon dioxide levels decrease. Uplift of the Colorado Plateau in the early Neogene contributes to these climate trends. On the timescale of millions of years, changes in paleogeography are predicted to have been more important to the climatic evolution of this region than changes in past carbon dioxide levels.

The climate predictions presented here are a first-order view of climatic change computed from basic physical principles in response to specific forcing factors. The strength of this approach is that the predicted climate is derived from a global perspective and is independent of the regional observations.