While Earth's position relative to the sun, the concentration of various greenhouse gases in the atmosphere, and the location of Earth's continents upon the globe change througout geologic time, the physical laws which dictate how the climate reacts to these phenomenon remain constant. Because of this continuity, Global Circulation Models are excellent tools by which to investigate both future climate change, and the climates of deep time.
Plio-Pleistocene Climate Evolution
The occurrence of large ice sheets on Earth is more of an exception than a rule: the geologic record indicates that ice ages amount to less than 10% of Earth's history. Our lab explores the peculiarity of these ice ages, from times of full-scale global glaciation (Snowball Earth - see below), to the late Cenozoic Ice Age we currently occupy. Although the Antarctic Ice Sheet developed early on (~35 Ma), the great Northern Hemisphere Ice Sheets first appeared on the scene in the latest Pliocene (~3 Ma). These ice masses severely altered the global climate, for instance, by changing planetary albedo as well as the general circulation of our atmosphere and oceans. The geologic record indicates that Earth’s environment has repeatedly endured abrupt disintegrations of the Ice Sheets since their inception, triggered by only gradual changes in Earth’s orbit around the Sun. We aim to understand how and why Earth’s environment evolved to become so precarious since the latest Pliocene and what mechanisms govern its chaotic behavior.
Cretaceous Greenhouse Climate
The Cretaceous (65-144 Ma) is one of the warmest time periods in the Earth's history. Sedimentary records show that Polar Regions could be as warm as 20°C and low latitudes were warmer than 35°C. The warming is mostly attributed to high concentrations of greenhouse gases. Hence, the Cretaceous could provide clues about how the Earth system could respond to future global warming. However, greenhouse gases cannot explain the low equator-to-pole temperature gradient. What mechanisms cause the low temperature gradient is still on debate.
By 100 Myr ago, plate tectonic processes had broken the giant Pangaean continent into separate smaller continents, and flooding of these continents by shallow seas further reduced the extent of dry land. (From: D. Marrits et al., Environmental Geology, 1997)
Late Paleozoic Ice Age Cyclicity
The coalescence of Earth’s continents into Pangea was accompanied by disparate and dynamic climate change. Both the Carboniferous and early Permian were dominated by the cyclic advance and retreat of massive Southern Hemisphere ice sheets, while the late Permian saw a transition into one of Earth’s longest-lived Greenhouse climates. Our research group explores the late Paleozoic climate on multiple temporal scales. Over the long-term, we seek to understand the gradual transition of a Carboniferous ice house climate, to a late Permian greenhouse. On shorter temporal scales we investigate the climate dynamics behind cyclic (~100 ka) glacioeustatic changes recorded in stable isotopes and Northern Hemisphere sedimentary sequences