Influence of temporally varying weatherability on CO<sub>2</sub>-climate coupling and ecosystem change in the late Paleozoic

Abstract

Abstract. Earth's penultimate icehouse period, the late Paleozoic ice age (LPIA), was a time of dynamic glaciation and repeated ecosystem perturbation, which was under conditions of substantial variability in atmospheric pCO2 and O2. Improved constraints on the evolution of atmospheric pCO2 and O2∕CO2 ratios during the LPIA and its subsequent demise to permanent greenhouse conditions are crucial for better understanding the nature of linkages between atmospheric composition, climate, and ecosystem perturbation during this time. We present a new and age-recalibrated pCO2 reconstruction for a 40 Myr interval (∼313 to 273 Ma) of the late Paleozoic that (1) confirms a previously hypothesized strong CO2–glaciation linkage, (2) documents synchroneity between major pCO2 and O2∕CO2 changes and compositional turnovers in terrestrial and marine ecosystems, (3) lends support for a modeled progressive decrease in the CO2 threshold for initiation of continental ice sheets during the LPIA, and (4) indicates a likely role of CO2 and O2∕CO2 thresholds in floral ecologic turnovers. Modeling of the relative role of CO2 sinks and sources active during the LPIA and its demise on steady-state pCO2 using an intermediate-complexity climate–carbon cycle model (GEOCLIM) and comparison to the new multi-proxy CO2 record provides new insight into the relative influences of the uplift of the Central Pangean Mountains, intensifying aridification, and increasing mafic rock to granite rock ratio of outcropping rocks on the global efficiency of CO2 consumption and secular change in steady-state pCO2 through the late Paleozoic.

High-precision U-Pb age constraints on the Permian floral turnovers, paleoclimate change, and tectonics of the North China block

“…A notable change to a more arid condition occurs across the major unconformity, which separates the upper Upper Shihhotse Formation subhumid paleosols containing abundant flora from overlying Sunjiagou Formation aeolian sandstone, carbonate breccias, and gypsum with few plant fossils. Aridification trends and analogous fossil-poor red beds have also been recorded in middle to low paleolatitudes during the Cisuralian to Guadalupian, concomitant with deglaciation of the late Paleozoic ice age (LPIA) and surge of atmospheric CO 2 (Tabor and Poulsen, 2008;Boucot et al, 2013;Schneider et al, 2019;Soreghan et al, 2019;Richey et al, 2020), except for Tethyan archipelagos where the ocean may have modulated climate (Figs. 2 and 3).…”

High-latitude ice and climate control on sediment supply across SW Gondwana during the late Carboniferous and early Permian

“…time scale, that were separated by discrete intervals of ice expansion reflects the sensitivity of the paleoglaciers to climate forcing. Moreover, the previously reconstructed U-Pb-calibrated glacial record is tightly coupled with long-term paleo-CO 2 estimates (Griffis et al, 2019a(Griffis et al, , 2019bRichey et al, 2020). These findings do not support a protracted deglaciation model driven by the tectonic drift of Gondwana away from the equator or one driven by orogenic collapse (Isbell et al, 2012;Limarino et al, 2014), as these processes, which operate on longer time scales (106-108 yr), are incompatible with the occurrence of the inferred deglaciations across SW Gondwana, which occurred on the <106 yr time scale (Griffis et al, 2019a).…”

“…The late Paleozoic ice age is Earth's penultimate glaciation and the only deep-time record of an icehouse-to-greenhouse transition in a world colonized by metazoan life and widespread tropical forests (Gastaldo et al, 1996). The demise of the late Paleozoic ice age was accompanied by major faunal and floral reorganization and changes in atmospheric chemistry, climate, and the hydrologic cycle (Montañez and Poulsen 2013;DiMichele, 2014;Richey et al, 2020). The sedimentary deposits of the Karoo, Kalahari, and Paraná Basins are among the highest-fidelity archives of the glaciation across southwestern Gondwana (Fig.…”

Trends and Rhythms in Climate Change During the Early Permian Icehouse

“…The ∼1.2 Myr cycles (green dashed curves) was Gaussian filtered using cutoff frequency of 0.00075 and 0.0009 cycles/kyr for MS series and 0.0007 and 0.001 cycles/kyr for GR series, respectively. Reconstructed atmospheric pCO 2 indicates a stepwise rise from a minimum across the Carboniferous-Permian boundary to maximum concentrations toward the end of the Sakmarian (Montañez et al, 2007;Richey et al, 2020). A rise in pCO 2 would not only promote the demise of the DSIII in the Karoo Basin on Gondwana but also enhance surface evaporation to desiccate the low latitudes (Figures 9d-9f).…”

“…Accumulation of the ice sheets year by year thus induced glacio-eustatic sea-level lowerings on the Pangaea continent (Figure 10f). Changes in subsidence rate and differential subsidence due to regional tectonic movements also can contribute to sea-level variations, but these abrupt and episodic movements cannot explain the periodicity in the (Montañez et al, 2007;Richey et al, 2020). (c) Record on Gondwana.…”