Daniel A. DixonDaniel A. Dixon 20th Century Forcing of the Antarctic AtmosphereClimate Change InstituteDepartment of Earth SciencesUniversity of Maine

•US ITASE traversed over >10,000 km•Drilled >40 ice cores

ITASE Traverse RoutesITASE Traverse Routes

Daniel A. Dixon US ITASE Traverse Routes and Ice Core Sites

ITASE Traverse RoutesITASE Traverse Routes

US ITASE SO4 time series (2005-1800 A.D.)

Pinatubo Agung

Daniel A. Dixon Ice Core Dating Accuracy

Cosiguina?Krakatau

Tambora

Daniel A. Dixon Ice Core Proxy for SH Westerlies

Warming causing intensification of the Southern Hemisphere westerlies and contraction of the Antarctic

circumpolar vortex

Seasonal mean pattern of 850mb zonal winds around Antarctica

Correlation field (nssCa and 850mb zonal winds 1948-2000)

Antarctic Oscillation (AAO)

AAO is the dominant pattern of Southern Hemisphere atmospheric variability south of 20ºS

nssCa Long Term Trend (1500-2000 A.D.)

01234567

150016001700180019002000

YEAR (A.D.)

ns

sC

a (

pp

b)

nss

Ca

(pp

b)

(From Yan et al., 2005)

Daniel A. Dixon Multiple Ice Core Non-Sea-Salt-Calcium Records

nssCa Records Positively Correlated with NCEP Zonal Winds

00-1 00-3 00-4 01-1

01-2 CWA-D SDM-94 UP-C

nssCa Records Positively Correlated with NCEP Zonal Winds

Jan-Dec 850mb Zonal Wind Correlation with Annual Ice Core nssCa

Correlation between~1950-1995 AAO (Thompson & Wallace, 2000) & normalized 2.5yr nssCa stack yields: r = 0.862 (>99.9% sig.)

US ITASE Normalized nssCa Stack Plot

Daniel A. Dixon RAMP DEM vs. Ice Core Site Elevation Grid Contours

Daniel A. Dixon RAMP DEM vs. Ice Core Site Elevation Grid Contours

Daniel A. Dixon nssCa Concentration Contours (1800-1995)

Daniel A. Dixon nssCa Spatio-Temporal Concentration Trends

1800 1850

1905 1945

1995

Daniel A. Dixon Conclusions

• nssCa concentration increases at multiple sites since ~1850 A.D.• Biggest increases occur in West Antarctica• Rate of nssCa increase increases ~1950! • nssCa spatial concentration maps… • Goal to create major-ion and trace-element concentration maps for entire continent

Daniel A. Dixon Questions…