Isotopes and Tree Rings

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.

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.

Hurricane Convection and Precipitation

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

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

 18 O (SMOW) ‰ P (mb) H. Olivia TX hurricanes “normal” precipitation Lawrence and Gedzelman 2002  18 O (SMOW) ‰ /14/177/29/1512/1 DATE CHANTAL ALLISON GROUND WATER Lawrence and Gedzelman 2001 Unusual  18 O in hurricanes Unusual  18 O in soil water

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

Hurricanes do not happen here Hurricanes happen here

Methods 1. Measure/crossdate tree rings using skeleton plots and COFECHA. 2. Seasonally-resolved sampling (earlywood, latewood for each year) using razor or microtome Methods 1. Measure/crossdate tree rings using skeleton plots and COFECHA. 2. Seasonally-resolved sampling (earlywood, latewood for each year) using razor or microtome Grissino-Mayer,2004 Lake Louise, Georgia 18 living trees 43 remnants, stumps, snags 61 total trees/94 measured radii Interseries correlation: 0.58 Average mean sensitivity: 0.35 Lake Louise, Georgia 18 living trees 43 remnants, stumps, snags 61 total trees/94 measured radii Interseries correlation: 0.58 Average mean sensitivity: 0.35

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

LW EW

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

Hurricane # August Hurricane # August Hurricane #7 30 Sep-7 Oct Hurricanes of 1871

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  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. 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  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.

del 18 O = 4.99 ( o / oo ) 1953 : Hurricane Florence results of sub- sampling