Brewer-Wilson Seminar Series Past Events 2016 / 11
18
Nov
2016
12:10 p.m.
- 1 p.m.
MP606
Guido Vettoretti
Thermohaline Instability and the Formation of North Atlantic Super Polynyas during the Glacial
Climate variability recorded in Greenland ice cores over the past 100,000 years is interspersed by a number of rapid warming events. Each warming event is approximately 10 to 15 degrees C in annual average temperature at summit Greenland. Each of these events in the climate record is also estimated to have occurred in less than a couple of decades. A modelling simulation of the glacial climate with a fully coupled climate model reveals that the initial warming event is triggered by thermohaline instability under a North Atlantic covered by sea ice. The initial instability is characterized by the formation of a wintertime glacial super polynya at the beginning of each warming event. Afterwards, the resumption of the Atlantic Meridional Overturning Circulation (AMOC) from a reduced state occurs within a couple of decades. I will describe some of the interesting physics underlying the instability.
04
Nov
2016
12:10 p.m.
- 1 p.m.
MP606
Whitney Bader
40 years of atmospheric methane FTIR observations from a remote European site
Observation of solar radiation in the infrared have been performed since the mid-fifties at the International Scientific Station of the Jungfraujoch (ISSJ, Swiss Alps, 46.5°N, 8.0°E, 3580 m a.s.l.), in the framework of the Network for Detection of Atmospheric Change (NDACC, www.ndacc.org<http://www.ndacc.org>). Systematic monitoring of the chemical composition of the Earth's atmosphere started in 1984 by using two state-of-the‐art Fourier Transform InfraRed (FTIR) instruments, while grating spectrometers were used previously in the early 1950s, and from the mid-1970s onwards, covering 40 years of quasi-continuous solar observations. In this framework, I will discuss optimization of retrieval strategies from infrared solar observations and methane trend analysis.