Post date: Nov 4, 2015 2:57:25 AM
I'm attending the Graduate Climate Conference (GCC) at MIT, Woods Hole, MA.
Poster Title: Estimating the relative importance of weather and climate modes for Antarctic sea ice variability
Coauthor: Dennis L. Hartmann
Abstract:
The relationship between climate modes and Antarctic sea ice is explored by sorting the variability into intraseasonal, interannual, and decadal time scales. Cross-spectral analysis shows that geopotential height and Antarctic sea ice extent are most coherent at periods between about 20 and 40 days (the intraseasonal time scale). In this period range, where the atmospheric circulation and the sea ice extent are most tightly coupled, the dominant meteorological variabilities are associated with Rossby waves that are excited by weather dynamics, orography, and heat sources. These Rossby waves are not directly related to the El Niño Southern Oscillation (ENSO) nor the Southern Annular Mode (SAM), which have received much attention for explaining Antarctic sea ice variability. Lag regression analysis shows that Rossby waves move slowly eastward following the background flow. The southerly (northerly) wind anomalies push sea ice northward (southward) and provide cold (warm) advection. On the interannual time scale, ENSO and SAM become important, but Rossby modes remain important for sea ice. On the decadal time scale, if we remove the influence of the prominent interannual climate modes from the sea ice extent time series, the positive sea ice trends in Ross Sea and Indian Ocean become insignificant at 95 %. Thus the positive trends in Antarctic sea ice may be explained with known modes of natural interannual variability.
This work is in review:
Kohyama, T., and D. L. Hartmann (2015), Antarctic sea ice response to weather and climate modes of variability, J. Climate, , in minor revision