Williams University of North Texas Montri Choowong Chulalongkorn University Thailand Sumet Phantuwongraj Chulalongkorn University Thailand Peerasit Surakietchai ID: 531911
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Harry Williams - University of North TexasMontri Choowong - Chulalongkorn University, Thailand.Sumet Phantuwongraj - Chulalongkorn University, Thailand.Peerasit Surakietchai - Chulalongkorn University, Thailand.Thanakrit Thongkhao - Chulalongkorn University, Thailand.Stapana Kongsen - Chulalongkorn University, Thailand.Eric Simon - University of North Texas
Geologic records of Holocene typhoon strikes in the Gulf of Thailand;
a preliminary
link between extreme storms and climate
change
?Slide2
Typhoon strikes on the Gulf of Thailand coast are rare, but devastating. Typhoon Gay (1989)Category 3 typhoon at landfallover 800 fatalities in Thailand11-m-high swells US$497 million in lossesHow frequent are typhoons?Don’t know – there’s no long-term record.Thai Meteorological records start in 1951.Is typhoon variability tied to climate change?A millennial-scale record of typhoon strikes is required to explore linkages to climatic changes.
BACKGROUNDSlide3
Tropical Cyclone Storm SurgeSlide4
PALEOTEMPESTOLOGY - OBJECTIVEFind prehistoric typhoon-deposited sand layers in low-energy sedimentary environments.Sand layers are offshore/beach/dune sands that have been transported inland – “anomalous”Primary diagnostic for recognizing washover sand layers are sharp contacts between coarser sand layers and finer in-situ sediments.Slide5
Cha’am coastal marsh (site HW1)STUDY AREASSlide6Slide7
Kui Buri swales (site SRY)Slide8
CORING SITESSlide9Slide10
METHODSSlide11Slide12
RESULTS – EXAMPLES OF SAND LAYERSExamples of suspected storm-surge-deposited sand beds. a. Coarse sand bed (CS), with gravel-sized clasts at site V5, Cha’am. b. Multiple mud rip-up clasts (MRC) in a sand bed at site SRY 3,
Kui
Buri
. Both sand layers are enclosed by, and have sharp contacts with,
fine-grained marsh
or swale deposits.Slide13
STRATIGRAPHY – CHA’AMSlide14
KUI BURISlide15
At each site, radiocarbon dates were used to construct age-depth models , which were used to estimate the age of each sand layer.DATING THE SAND LAYERSSlide16
Estimated ages of typhoon strikes at Cha’am and Kui Buri. Horizontal line through data points represents period of record at each site. Yellow boxes represent potentially coeval typhoon strikes recorded at both sites.Fifteen typhoon strikes (including coeval strikes) in 8800 years.Typhoon strikes over three times as frequent in 3500-7000 cal. yr BP than in 0-3500 cal. yr BP.Slide17
WHAT COULD HAVE CAUSED TYPHOONS TO BE MORE FREQUENT IN THE MID-HOLOCENE?Increased Northern Hemisphere solar forcing in the mid-Holocene resulted in the Mid Holocene Warm Period. In the North Pacific, ENSO activity was reduced during this period. There is evidence that suppressed ENSO activity causes an westward shift in tropical cyclone genesis location. As a result, tropical cyclones are more likely to follow more southerly storm trajectories, striking South East Asia (including Thailand); under enhanced ENSO conditions, an eastward shift in tropical cyclone genesis location results in more northward recurving trajectories, leading to greater likelihood of tropical cyclone strikes on Japan and Korea.Slide18Slide19
Study results from Thailand appear to support this model of an oscillating pattern in tropical cyclone activity between the northern and southern western North Pacific.Slide20
PRELIMINARY CONCLUSIONS/QUESTIONS 1. Sand layers most likely record typhoon strikes. Evidence: rarity, sharp contacts, gravel-sized clasts, mud rip-up clasts, plant fragments, offshore foraminifera (in some layers).2. Preliminary evidence of more frequent typhoons in the mid-Holocene (3500-7000 cal. yr BP). Could this be a result of an ENSO-driven oscillating pattern of typhoon activity between the southern and northern western North Pacific? 3. Could another climatic “warm period” (ongoing global warming) cause an increase in typhoon strikes in Thailand? 4. More work is required to improve age control and confirm a mid-Holocene tropical cyclone hyper-active period in SE Asia.Acknowledgments: This material is based upon work supported by the National Science Foundation under Grant No 1305787. Thailand Research Fund (TRF:BRG5780008) and Chulalongkorn University (CU57-058-CC), a UNT Charn Uswachoke International Development Fund award and a grant from the UNT Small Grants Program.