Recent decades of climate and cryospheric change on

Recent decades of climate and cryospheric change on the Antarctic Peninsula David G. Vaughan British Antarctic Survey

Climate Warming - Antarctica Source: Vaughan et al. Climatic Change, 2002

Antarctic Peninsula melt - Mean annual air temp

Part 1 - More melt… Vaughan, D. G. , 2006: Recent trends in melting conditions on the Antarctic Peninsula and their implications for ice-sheet mass balance. Arctic, Antarctic and Alpine Research, 38(1), pp. 147 -152.

Faraday/Vernadsky mean annual temperature Source: BAS

Faraday/Vernadsky – seasonal trends Source: BAS

Antarctic Peninsula Fossil Bluff 1985/86 Fossil Bluff 1996/97 Source: DGV

…quantitative – Rothera ramp Source: Andy Smith

Antarctica Peninsula - orientation

Annual PDDs

Antarctic Peninsula melt - Station trends

Parameterisation of ann. temp vs. PDDs Figure 3. Correlation of mean annual air temperature to positive degree-days for all Antarctic Peninsula station data. East coast sites are represented by open circles and have a best fit regression line (solid) of, Φ = 1089 e (0. 261 T / ˚C) (r 2 = 0. 84). West coast sites are represented by black triangles and have a best-fit regression line (dashed) of, Φ = 358 e (0. 251 T / ˚C) (r 2 = 0. 79).

Melt-day distribution 2000 1950 2050 Figure 4. Distribution of annual positive degree-days calculated for a. 1950 (i. e. 2000 – 2. 5˚C), b. 2000 and c. 2050 (i. e. 2000 – 2. 5˚C).

Antarctic Peninsula melt - Mass balance and runoff

Conclusions • Parameterization of the number of PDDs as a function of mean annual temperature allows mapping of change • Increasing surface ablation was estimated and shown to be likely to have doubled between 1950 and 2000, and given continued summer warming could double or treble by 2050. • Runoff was calculated. At present it is (0. 008 - 0. 055) mm a-1 of sea level rise with the likelihood that with continued warming it will perhaps treble within 50 years. Increasing uncertainty • Long-term meteorological station data show increased duration of melt conditions across the Antarctic Peninsula over the past 50 years

Part 2 - Shortening glaciers… Cook, A. J. Fox, D. G. Vaughan, and J. G. Ferrigno, 2005: Retreating glacier-fronts on the Antarctic Peninsula over the last 50 years. Science, 22, pp. 541 -544.

Sheldon Glacier 1957 1986 1969 1998 2001

Analysis of glacier-front changes 1970 - 1975 -1980 - 1985 -1990 - 19951974 1979 1984 1989 1994 1999 Extract from table showing mean change per year observed in 5 -year intervals

Change in glacier length

Complete population

Latitude Sectors

Part 3 - Faster glaciers… H. Pritchard and D. G. Vaughan, in prep.

Tracking features in radar (SAR) images SAR 1 +35 days measurement = (glacier flow) & (orbit offset) random error systematic error SAR 2

Tracking error: the case for azimuth-direction data 2) range azimuth Range direction Azimuth direction 1) 1 5

Tracking features in radar (SAR) images • 150 scenes • 70 000 km 2 • 337 glaciers • 9 summers 0 0 md-1 15 4 30

Change in flow speed 1993 to 2003 Change in flow speed % that accelerated +7. 8 % 60% +14. 2 % 65% +14. 4 % 65% +12. 7 % 67% +13. 4 % 75% (± 0. 5 to 0. 7%) (by > 5%)

Retreat rate +8% 64 °S +14% 10 % +14% +13% 68 °S Cook et al. (2005) 0

Conclusions • Significant, widespread speed-up • Appears driven by retreat • Response to strong regional warming

Conclusions Antarctic Peninsula contribution to sea level: AP runoff: Shelf collapse (Rignot et al. 2004): up to AP flow imbalance (12%, 1993 -2003): at least 0. 06 mm /yr Total: Alaska melt (Arendt et al. 2002): 0. 06 mm /yr 0. 07 mm /yr 0. 19 mm /yr 0. 14 mm/yr

Conclusions