Focus on High Latitudes State of the Antarctic & Southern Ocean Climate System

Focus on High LatitudesState of the Antarctic & Southern Ocean Climate SystemAuthors: P. A. Mayewski, M. P. Meredith, C. P. Summerhayes, J. Turner, A. Worby, P. J. Barrett, G. Casassa, N. A. N. Bertler, T. Bracegirdle, A. C. Naveira Garabato, D. Bromwich, H. Campbell, G. S. Hamilton, W. B. Lyons, K. A. Maasch, S. Aoki, C. Xiao, and Tas van Ommen.

Reviews of Geophysics, 47, RG1003/2009. Paper Number 2007RG000231.

Work in Progress

Annular modes are hemispheric-scale patterns of climate variability. The most popular example of a large scale pattern of climate variability is the El-Nino/Southern Oscillation (ENSO).  

ENSO owes its existence to coupled ocean/atmosphere interactions in the tropical Pacific. ENSO is the most important (in terms of variance explained) pattern of large scale climate variability in the tropicsannular modes owe their existence to internal atmospheric dynamics in the middle latitudes. The annular modes are the most important patterns of climate variability in the Northern and Southern Hemisphere middle and high latitudes.  

There are two annular modes in Earth's atmosphere: a Northern annular mode (NAM) and a Southern annular mode (SAM). These are important because  

Annular modes explain more of the synoptic and annual variability in the extratropical atmospheric flow than any other climate phenomenon.Annular modes impact climate throughout much of their respective hemispheres.  

The NAM is associated with large anomalies in surface temperatures and precipitation across North American and Eurasia, in the distribution of sea-ice throughout the Arctic, in sea-surface temperatures over the North Atlantic, and in the spatial distribution ozone in the lower stratosphere.

The SAM is linked to variations in temperatures over Antarctica, sea-surface temperatures throughout the Southern Ocean, and the distribution of sea-ice around the perimeter of Antarctica

Figure 1. Geographical location

Figure 2. Key elements of the A&SO climate system

• bathymetry • winds (at 10 m) • correlation between

Southern Oscillation Index (remember ENSO) and surface atmospheric pressure field • correlation between

the Southern Annular Mode Index (SAM) and surface atmospheric pressure field

Figure 2. Key elements of A&SO climate system

• rate of accumulation of precipitation • seasonal maximum

and minimum of sea ice field• spatial variability of

Na (a sea-salt aerosol) concentration, from snow samples & firn cores• spatial variability of

sulphate (used to reconstruct biological activity & volcanic eruptions) concentration, from snow samples & firn cores

Figure 3 shows the main climatic events of the last 65 MA focusing on the Antarctic context and Figure 5 shows them for the last 1MA.

Figure 4. Change in average global temperature over the last 80 MA, plus future rise expected from energy use projections.

Figure 3 shows the main climatic events of the last 65 MA focusing on the Antarctic context and Figure 5 shows them for the last 1MA.

Figure 6. Methane synchronization of the ice core records of δ18O as a proxy for temperature

Figure 7. Comparison between Antarctic and Greenland climate change over the Holocene period. The data shown is used to examine (1) potential control on climatic changes and (2) sequence of changes

Figure 7. (continued) Comparison between Antarctic and Greenland climate change over the Holocene period. The data shown is used to examine (1) potential control on climatic changes and (2) sequence of changes

Figure 7. (continued)

Figure 8. Main climatic events of the last 12,000 years: the Antarctic context. NH, Northern Hemisphere; SH, Southern Hemisphere; WA, West Antarctica; EA, East Antarctica; MDV, McMurdo Dry Valleys.

Figure 9.

Top: Figure 10 shows near-surface temperature trends (from long records) and the statistical significance of the trends

Bottom: Figure 11 (reanalysis: observations and analysis) shows warming trend in the lower troposphere (~ 5 km)