Exploring Solar Influence on Indian and North
Atlantic Ocean Sea Surface Temperatures Across
the Last Millennium
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May 5, 2024
Introduction
▶ Paleoceanography and Paleoclimatology
▶ Study of long-term environmental changes in oceans and
climate
▶ Reconstruction using proxy data (ice cores, marine fossils,
sediment layers, etc.)
▶ Reconstruction of Sea Surface Temperature (SST)
▶ UK37 Saturation Index (alkenones from marine algae)
▶ Mg/Ca ratio of foraminiferal test
▶ TEX86 (membrane lipids from archaea)
Climatic Events
▶ Medieval Climate Anomaly (MCA): 900 AD - 1250 AD
▶ Warmer conditions in North Atlantic region
▶ Potential causes: increased solar activity, reduced volcanic
activity, ocean circulation changes
▶ Little Ice Age (LIA): 1450 AD - 1850 AD
▶ Cooler temperatures, glacial advances
▶ Regional variations in timing and extent
▶ Current Warm Period (CWP): Global warming since
industrialization
Solar Link to Climate during the Last Millennium
▶ Solar activity and radiative climate forcing
▶ Sunspot cycles, grand solar minima (e.g., Maunder Minimum)
▶ Cosmic ray intensity and cosmogenic isotopes (14C, 10Be)
▶ Total solar irradiance (TSI) reconstructions
▶ Empirical Sun-Climate connections
▶ Periodicities in climate data matching solar cycles
▶ Correlations between solar activity and climate parameters
Objectives
▶ Compare reconstructed SST of Indian and North Atlantic
Ocean during the last millennium
▶ Ascertain the impact of climatic events on SST
▶ Characterize the solar influence on SST
Data and Locations - North Atlantic Ocean
▶ 10 proxy records from Norway, Iceland, Scotland, and Rockall
Trough
▶ Proxies: alkenones, foraminifera, diatoms
▶ Validated against instrumental SST data
Data and Locations - Indian Ocean
▶ 6 proxy records from Indian Ocean and Indo-Pacific warm pool
▶ Proxies: alkenones, foraminifera
▶ Validated against instrumental SST data
Results and Discussion - North Atlantic Ocean
▶ Warmer SSTs during 20th century and MCA, cooler during
LIA
▶ Correlations with Atlantic Multidecadal Oscillation (AMO)
▶ Comparisons with air temperature reconstructions
Results and Discussion - Indian Ocean
▶ Warming trend during MCA and CWP, cooling during LIA
▶ Freshening trends in LIA, role of ITCZ migration
▶ Magnitude of LIA cooling compared to last glacial maximum
Results and Discussion - Solar Forcing
▶ Coincidence of solar minima (e.g., Maunder Minimum) with
cooling events
▶ Potential mechanisms: TSI changes, cosmic ray flux,
atmospheric coupling
▶ Role of solar forcing vs. other drivers (e.g., greenhouse gases)
Conclusion
▶ Elucidated SST variability in Indian and North Atlantic Oceans
▶ Identified impacts of climatic events like MCA, LIA, and CWP
▶ Highlighted the role of solar forcing in shaping SST patterns
▶ Insights into natural drivers of climate variability and oceanic
behavior
References