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North Atlantic Ocean Multi-Decadal Variability & its Impact on Hurricanes and Landfalls

This presentation explores the potential driver of Atlantic thermohaline circulation and its effects on hurricane activity in the Atlantic basin and United States landfalls. It concludes that multi-decadal variability in sea surface temperatures and sea level pressures is likely driven by changes in the strength of the Atlantic Thermohaline Circulation (THC).

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North Atlantic Ocean Multi-Decadal Variability & its Impact on Hurricanes and Landfalls

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  1. North Atlantic Ocean Multi-Decadal Variability Phil Klotzbach Department of Atmospheric Science Colorado State University Climate Diagnostics and Prediction Workshop October 23, 2007

  2. Outline • Potential driver – Atlantic thermohaline circulation • Effects on Atlantic basin hurricanes • Effects on United States hurricane landfalls • Conclusions

  3. 160oW 20oE

  4. SURFACE 500 METERS

  5. Salt Water Density Fresh Water Density

  6. H H 3 1 2 Courtesy of John Marshall (MIT)

  7. NADW Tropics THC - Strong THC - Strong 20 Sr 20 Sr Negative buoyancy Positive buoyancy NADW THC - Weak THC - Weak 10 Sr 10 Sr Positive buoyancy Negative buoyancy

  8. STRONG THC WARM

  9. SSTA + SSTA - + – – SLPA – + SLPA + gyre - gyre + + – STRONG THC WEAK THC

  10. THC Index (SST – SLP)

  11. Top 20 THC Years – Bottom 20 THC Years (1878-2006) - SST

  12. Top 20 THC Years – Bottom 20 THC Years (1878-2006) - SLP

  13. FAST SLOW FAST SLOW Thermohaline Circulation Rate of Salt Buildup from (E-P) - River = 0 Salt Anomaly (S1) (S1) (S1) YEARS 30 60 90 120

  14. Top 20 – Bottom 20 THC Ratios

  15. THC STRONG CAT 3-4-5 TRACKS THC WEAK CAT 3-4-5 TRACKS

  16. 1950-1964 1997-2006 25 YEARS13 Major Hurricanes 1970-1994 25 YEARS3 Major Hurricanes 54 55 THC STRONG THC WEAK 85 54 55 54 60 89 59 04 50 92 05 04 50 60

  17. FLORIDA LANDFALLING MAJOR HURRICANES 1 3 11

  18. Conclusions • Multi-decadal variability in Atlantic basin sea surface temperatures and sea level pressures exists and is likely driven by changes in strength of the Atlantic thermohaline circulation • Atlantic basin tropical cyclone activity (and especially major hurricane activity) is much more frequent during strong THC years • Florida peninsula and East Coast landfalls are dramatically altered by THC phase changes

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