Environmental Science and Engineering Seminar

Dr. Pavia: Sea ice coverage in the Arctic Ocean has seen a consistent decline over the past 40 years, coincident with anthropogenic warming. Climate models disagree in their projections of when the Arctic Ocean will experience ice-free summers under different warming scenarios. Paleoclimate records offer a potential route towards understanding Arctic ice extent under periods of warmer climate than present, sea ice is particularly difficult to reconstruct from proxy records. In this talk I will show new data suggesting that helium-3 concentrations in marine sediments, derived from the input of interplanetary dust particles, can be used to reconstruct ice coverage and melting in the Arctic Ocean. I will then briefly discuss the possible applications of this proxy to answer outstanding questions regarding Arctic ice coverage during paleoclimate intervals both colder (e.g. LGM, Marine Isotope Stage 4) and warmer (e.g. Marine Isotope Stage 5, Pliocene Warm Period) than present.

Dr. Novak: Many aspects of midlatitude planetary turbulence on Earth can be explained using linear baroclinic theory for a differentially heated rotating fluid. However, the observed seasonal cycle of this turbulence deviates from the baroclinic theory in some winters, with the deviation being most pronounced over the North Pacific. Since its discovery in the 90s, this deviation has received much research attention, yet its causes remain undetermined. With a hierarchy of model complexity, we show that this deviating behavior is a general feature of all rotating planetary motions that are in the vicinity of sufficiently strong and/or equatorward sub-tropical jets. This phenomenon can be explained using the steady-state eddy-kinetic-energy (EKE) budget. We reformulate this budget as a steady-state prediction for the EKE, given the background-flow and externally imposed eddy sources. This behaviour is also likely to occur on other planets with strong enough sub-tropical jets.