Arctic Environmental Change across the Pliocene-Pleistocene Transition

• Main Author: Keisling, Benjamin Andrew
• Format: Thesis
• Language: unknown
• Published: University of Massachusetts Amherst 2015
• Subjects: Arctic; Sea ice
• Online Access: https://dx.doi.org/10.7275/6955394; https://scholarworks.umass.edu/masters_theses_2/228

Environmental change in the Arctic proceeds at an unprecedented rate. The Pliocene epoch (5-2.65 million years ago) represents an analog for future climate conditions, with p CO 2 and continental configurations similar to present. Yet conditions in the Pliocene Arctic are poorly characterized because of sparse sampling. The records that do exist indicate periods of extreme warmth, as well as the first expansion of large ice-sheets in the Northern Hemisphere, took place from the end of the Pliocene into the early Pleistocene. Understanding these deposits and their implications for our future requires developing a sense of climatic evolution across the Plio-Pleistocene transition and especially during the intensification of Northern Hemisphere Glaciation (iNHG) ~2.7 million years ago. Here we reconstruct environmental change in the Arctic using a suite of organic geochemical proxies in a sedimentary archive recovered from Lake El'gygytgyn, Arctic Northeast Russia. We use the distribution of branched glycerol dialkyl glycerol tetraethers (brGDGTs) and the hydrogen isotopic composition (δD) of plant leaf-waxes ( n -alkanes) to reconstruct relative temperature change across the interval spanning 2.8 to 2.4 million years ago. Our work demonstrates that, following the first major glaciation of the Northern Hemisphere, it took multiple glacial cycles for the Arctic to become synchronized with the climatic changes recorded in the deep ocean. This work has implications for understanding the role of sea-level, sea-ice, vegetation and carbon-cycle feedbacks in a changing Arctic.