Changes in Sea Ice Alison Liou Meghan Goodwin

Arctic Oscillation (Northern Annular Mode) Antarctic Oscillation (Southern Annular Mode) Zonal = movement along the lines of latitude Meridional = movement along the meridian Antarctic oscillation is a similar pattern, characterized by the counterclockwise circulation of westerly winds Similar positive and negative phases

Empirical Orthogonal Function (EOF) Analysis – Used by Overland et al to analyze atmospheric circulation patterns such as the Arctic Oscillation – Used to study spatial patterns of variability and their changes through time – Takes spatial patterns over time and finds orthogonal patterns to explain the maximum amount of variability *Demonstration!*

Geopotential Height Approximation of a pressure surface above mean sea level Lower in cold air masses (because cold air more dense) Higher in warm air masses (because warm air less dense) Geopotential height anomalies refer to deviations from average values – Positive values = higher than average = warmer than average – Negative values = lower than average = colder than usual 850 hPa Geopotential Height Anomalies Meters

Pacific North American Pattern Fluctuations in East Asian Jet Stream – Positive Phase Western US: higher geopotential heights, warmer temperature Southeastern US: lower geopotential heights, lower temperatures – Negative phase: Western US: lower geopotential heights, lower temperatures Southeastern US: higher geopotential heights, warmer temperature PNO positive phase by month Geopotential height anomaly

Overview of the Readings Overland et al 2008: Analyze the different patterns in arctic and Antarctic sea ice changes. Do these changes make sense? Overland et al 2010: Claim that recent Arctic sea ice loss is due to shifting climatic patterns. Introduce idea of Arctic Dipole. Loss of sea ice leads to feedback patterns that shift broader atmospheric circulation. Screen and Simmonds 2010: Discuss Artic amplification and how loss of sea ice is causing more loss of sea ice. Maksym et al. 2012: Discuss Antarctic sea ice trends and the properties of Antarctic sea ice.

Questions to Consider Is Arctic sea ice melting caused by anthropogenic affects? How do the patterns of increasing Antarctic sea ice and decreasing Arctic sea ice compare? What does this mean for future climate models?