Global change in continental climate during the Paleocene-Eocene Thermal Maximum: a view through the window of terrestrial palynology

Abstract:

We compiled data on terrestrial palynomorphs across the Paleocene-Eocene Thermal Maximum (PETM) from 38 sites spanning high southern to high northern latitudes. These records provide evidence for latitudinally differentiated floral responses to continental climate change during the PETM. In high-paleolatitudes of the northern hemisphere, Cupressaceae (dawn redwood, bald cypress and allied genera) increased in relative abundance, while in the high-latitudes of the southern hemisphere, Araucariaceae (Wollemi pine) pollen increased. These increases are consistent with a shift to wetter and warmer climates at high-paleolatitudes during the PETM compared to the latest Paleocene. In contrast, mid-paleolatitudes in the northern hemisphere experienced increases in the relative abundance of Arecaceae (palm), Bombacoideae (silk cotton tree and relatives) and Fabaceae (legume) pollen at the expense of Pinaceae (pine family) and Cupressaceae. This is consistent with warmer and drier or more seasonally dry climates. Greater seasonal water stress in mid-paleolatitudes, perhaps associated with more frequent fires, may also have led to opening of forest canopies and the increased abundance of sun-demanding taxa such as Anemiaceae (flowering fern). At low-paleolatitudes the increased relative abundance of Arecaceae (palm), Bombacoideae (silk cotton tree and relatives) and Fabaceae (legume) pollen also suggests warmer and possibly more seasonally dry climates. We infer Köppen climate types from latest Paleocene and PETM palynological assemblages using the nearest living relative approach and compare these with changes in Köppen climate type across the same interval deduced from Community Earth System Model (version CESM1.2) simulations for the same sites to see if the two sources of information are congruent. Inferences from palynological assemblages are mostly consistent with modelled climate changes.