Isotopes and Tree Rings

1. Isotopes and Tree Rings

2. Isotopes in Tree Rings • Environmental processes captured in tree rings can be embodied either physically or chemically. • Chemical properties involve (1) individual elements, (2) chemical compounds, and (3) stable isotopes. • Individual elements and chemical compounds often indicate pollution events, i.e. exogenous disturbance pulses and trends. • Examples • lead from gasoline • nickel contamination in groundwater • titanium from natural sources • Isotopes indicate past changes in environmental processes that cause differences in the relative proportions of an element’s isotopes. • Isotopes: Atoms with the same number of protons, but differing numbers of neutrons. Isotopes are different forms of a single element.

3. Isotopes: Atoms with the same number of protons, but differing numbers of neutrons. Isotopes are different forms of a single element. • Isotopes indicate past changes in environmental processes that cause differences in the relative proportions of an element’s isotopes. • Example: Carbon 12 and Carbon 13 are both isotopes of carbon, one with 6 neutrons and one with 7 neutrons (both with 6 protons). • Example: Oxygen 16, Oxygen 17, and Oxygen 18 are both isotopes of oxygen, one with 8 neutrons, one with 9 neutrons (rare), and one with 10 neutrons (both with 8 protons). • Reference = Vienna Standard Mean Ocean water (VSMOW) for oxygen and Vienna PeeDee (River) Belemnite (VPDB) for carbon.

6. Hurricane Convection and Precipitation

7. Lawrence, J.R. 1998: Isotopic spikes from tropical cyclones in surface waters: Opportunities in hydrology and palaeoclimatology. Chemical Geology 144: 153-160.

8. Hypothesis: Hurricane precipitation results in 18 O-depleted latewood cellulose. Therefore, hurricane events can be identified by values of D18O (earlywood – latewood) >> 0.

9. 200 Lawrence and Gedzelman 2002 “normal” precipitation Unusual d18O in hurricanes 400 P (mb) H. Olivia 600 800 Lawrence and Gedzelman 2001 5 TX hurricanes GROUND WATER -10 -30 -20 -15 -5 -25 0 d18O (SMOW) ‰ d18O (SMOW) ‰ -5 ALLISON -10 Unusual d18O in soil water CHANTAL -15 2/1 4/17 7/2 9/15 12/1 DATE

11. Sandy Isle Pinus palustris Francis Marion NF Valdosta Big Thicket Eglin AFB

14. Hurricanes happen here Hurricanes do not happen here

15. Methods 1. Measure/crossdate tree rings using skeleton plots and COFECHA. 2. Seasonally-resolved sampling (earlywood, latewood for each year) using razor or microtome Lake Louise, Georgia 18 living trees43 remnants, stumps, snags 61 total trees/94 measured radii Interseries correlation: 0.58 Average mean sensitivity: 0.35 Lake Louise, Georgia 18 living trees43 remnants, stumps, snags 61 total trees/94 measured radii Interseries correlation: 0.58 Average mean sensitivity: 0.35 Grissino-Mayer,2004

16. 3.Remove pine resins and other extractives (Loader et al., 1997; sonification) to yield α-cellulose. 4. Run ~80 ug through mass spec α-cellulose

18. EW LW

19. To remove trends that might mask the hurricane signal, perform AR-1 modeling Residuals < –1 are associated with hurricane activity Many residuals> –1 and < –0.5 are also associated with hurricane activity Most residuals > +1 are associated with known droughts

21. Hurricanes of 1871 Hurricane #417-30 August Hurricane #314-23 August Hurricane #730 Sep-7 Oct

22. PROXY RECORD OF HURRICANES • Between 1770 and 1997, we found no hurricane event where residual is > –0.5. • 1950s was the busiest decade since 1870s. • Little activity between 1881 and 1930. • Significant activity from 1840 until 1880 (especially 1870s). • Unrecognized events in 1847, 1857, and elsewhere. New historical evidence since found for 1857 event. • Only two decades with no hurricane activity, 1830s and 1890s. • First U.S. record of “Great Hurricanes of 1780” that affected Caribbean region.

23. 1953 : Hurricane Florence results of sub-sampling del18O = 4.99 (o/oo)