Exploring the spatial patterns of changing surface ocean conditions in the Tropical Atlantic and Pacific Kilbourne, K.H., D. E. Black, J. Nyberg, T. M. Quinn, R. S. Webb, A. Winter

Main Points Don’t forget the rest of the tropics. Interactions between the ocean basins can be important Atlantic Perspective on the LIA

Questions What is the state of knowledge of Caribbean climate history? How do the spatial patterns tie into the Pacific climate history Are the patterns consistent with known inter-basin connection mechanisms?

Earlier work in Tropical Atlantic SST –Centennial resolution –Short records –Indicated cooler conditions during the Maunder Minimum –Some hint of changes in seasonal range Examples: –Keigwin et al., 1996 (Bermuda) –Winter et al., 2000 (Puerto Rico) –Watanabe et al., 2001 (Puerto Rico) –Nyberg et al., 2002 (Puerto Rico)

World Ocean Atlas 2001 Annual SST x x

Example of Resolution Nyberg et al., Artificial Neural Network

Hasse-Schramm et al., 2003 Black et al., 2007 Kilbourne et al in process 2007 TemperatureTemperature Higher Lower New SST data: High resolution

Centennial-scale Puerto Rico Coral  18 O driven by SST SST proxy SST and SSS proxy

Hasse-Schramm et al., 2003 Black et al., 2007 Kilbourne et al in process 2007 TemperatureTemperature Higher Lower Pacific MCA New SST data: High resolution Galapagos P>E All agree 2˚C cooler

Local and Regional Surface Temperature Anomalies Track Hemispheric Anomalies

World Ocean Atlas 2001 Annual SST x x x x

Hasse-Schramm et al., 2003 Black et al., 2007 Kilbourne et al in process 2007 TemperatureTemperature Higher Lower Pacific MCA Seasonal Perspective

LPTA E1P ~ Monthly Coral Data

Seasonal Range in  18 O No large changes in seasonality evident from the  18 O Coral  18 O = f( SST and  18 Ow) so a seasonally resolved independent temperature proxy is needed to confirm.

Atlantic -Pacific Linkages

Atmospheric Link Zhang and Delworth (2005) –Modeled a shut down of THC –Resulted in Anomalous Hadley Circulation –Cooling in tropical Atlantic => SLP –Across the Isthmus, SLP too

Atmospheric Link Chunzai Wang (2006) “An overlooked feature of tropical climate: Inter-Pacific-Atlantic variability” –Examined the effects of SST gradient between Pacific and Atlantic equatorial regions –Resulted in anomalous Walker Circulation –Positive feedback –Far field effects in Pacific South America ColdWarm Wind Anomalies Colder Convergence Amplification of Pacific Walker Anomalies

Coral Data from NCDC

Difference ~ from ~ Coral data available from NCDC

Summary of Tropical LIA Spatial Pattern Cooler Caribbean and Gulf of Mexico Warmer and Drier in Southwestern Pacific Potentially warmer/wetter in cold Tongue Enhanced SST Gradient between Atlantic and Pacific

Could This Mechanism Be Working During the LIA? What other processes could be at work? South America ColdWarm Wind Anomalies Colder Convergence Amplification of Pacific Walker Anomalies

Suggestion The way to really get at processes and mechanisms is data assimilation Despite best efforts, data are often chosen because they fit a story Need an objective way to handle the errors in proxies and dating - cost functions

Selected Previous work in the Caribbean Keigwin et al., 1996 (Bermuda) – ~1˚C cooler during the Little Ice Age Winter et al., 2000 (Puerto Rico) –Coral  18 O in 5-year segments –2-3˚C cooler during Maunder Minimum –The  18 O is a combined signal of SST and  18 Ow Watanabe et al., 2001 (Puerto Rico) –Paired Mg/Ca and  18 O –Found 2-3˚cooler during (really ~ ) –Hiatus visible in core x-ray - dating off by ~200 years Nyberg et al., 2002 (Puerto Rico) –Foraminiferal abundances - artificial neural network –Increased seasonal SST range ~