Thursday, October 13, 2011, 4:30AM - 5:30AM
Full title of talk: "A lake sediment record of Arctic Holocene climate using a multi-proxy study of aquatic primary productivity." Lake sediment core records are useful in the reconstruction of long-term regional climate. In arctic environments, lacustrine primary productivity is largely controlled by climate through alteration of the duration of ice-free conditions. In warmer times with longer ice-free seasons, total aquatic productivity is increased and species such as green algae and higher plants are more abundant. In colder times, diatoms predominate because their ability to bloom in early summer leaves them less impacted by the shortened growing season. Through the measurement of multiple productivity proxies such as carbon and nitrogen concentrations as well as stable isotopes, algal pigments and diatom species assemblages, a detailed understanding can be gained of the species shifts and changes in the total magnitude of primary productivity throughout the record. This can then be applied to reconstructing the regional climate history. In Qivitu Highlands Lake, located on eastern central Baffin Island in the Canadian Arctic, these proxies are used to develop a record of the last 10,500 years. The early part of the record shows strong early Holocene warmth with neoglacial cooling beginning approximately 6000 years BP. The strongest climate event influencing the record in this region appears to be the Little Ice Age, where all proxies show major changes. Anthropogenic warming is seen in the most recent sediments. This site is particularly sensitive to changes in temperature due to its small size and shallow depth and should therefore accurately record rapid shifts in climate. As of now, the most promising part of this study is the ratio of the pigments lutein (green algae and higher plants) to diatoxanthin (diatoms and chrysophytes), which show that modern conditions have returned to a similar state as during the Holocene Thermal Maximum.