Evolution of Texas climate

Richard CasteelJackson School of Geosciences

11-24-09

Outline

• Modern day Texas climate• Climate change - varying resolutions

– Geologic indicators– Soil indicators– Fossils and isotopes– Tree ring data

• Current research

Modern Texas climate

• Hot, dry summers• Mild, dry winters• Wet springs/falls• High rate of PET• Hot spot for

climate change?

Geologic map of Texas

Ü0 320 640160 Kilometers

Geologic Map of Texas

Soil map of Texas

• Dominated by:– Thin, rocky soils

• Thicker in past– Upland soils– Cave deposits

Soil degradation - Sr isotopes

• Carbon dated soil deposits Hall’s Cave

• Gopher/voletooth enamel– Diet

• Hackberry seed fossils– Root position (Cooke et al, 2003)

Paleoclimate inferred from fossils and isotopes

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-5

-4

-3

-2

-1

0

1

2

Time before present (ka)

<----

cool

er---

--war

mer

---->

Last glacial maximum

24-14 ka.• Cooler and wetter

– Faunal evidence

– Pollen data

– Alluvium δ 13C valuesof -21‰

• C3 plant abundance

62 - 7273 - 7879 - 8283 - 8687 - 94

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0

1

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INFERRED TRENDS IN PALEOCLIMATE

Time before present (ka)

<----

cool

er---

--war

mer

---->

6-2 ka.

Warm/dry

period

6-2 ka.• δ 13C values

– Snail shells (Goodfriend and Ellis, 2000)

– Alluvium and soil (Nordt et al, 1994)

– More positive values =higher abundance C4 plants

1698-1980• Post oak chronology

• Annual resolution

• Calibrated with modern record

(Stahle and Cleaveland, 1998)

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June PDSI derived from tree rings

1690 1710 1730 1750 1770 1790 1810 1830 1850 1870 1890 1910 1930 1950 1970-8

-6

-4

-2

0

2

4

6

8

Central Texas

June PDSI

Date

June

PDS

I

(Data from Stahle and Cleaveland , 1988)

Drought of the 1950s

http://www.ncdc.noaa.gov/paleo/pdsidata.html

Drought of the late 1850s-1860s

http://www.ncdc.noaa.gov/paleo/pdsidata.html

Drought of the 1770s

http://www.ncdc.noaa.gov/paleo/pdsidata.html

Current research

• Extend the high resolution climate record– Past drought for water

planning

– Bald cypress trees

– Preliminary results

http://www.news8austin.com/content/your_news/default.asp?ArID=255153

QUESTIONS?