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Sept 20, 2013 Monica Arienzo

Global connections between aeolian dust, climate and ocean biogeochemistry at the present day and at the last glacial maximum Maher et al., 2010, Earth-Science Reviews. Sept 20, 2013 Monica Arienzo.

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Sept 20, 2013 Monica Arienzo

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  1. Global connections between aeolian dust, climate and ocean biogeochemistry at thepresent day and at the last glacial maximumMaher et al., 2010, Earth-Science Reviews Sept 20, 2013 Monica Arienzo

  2. REALLY COMPLEX: Global connections between aeolian dust, climate and ocean biogeochemistry at thepresent day and at the last glacial maximumMaher et al., 2010, Earth-Science Reviews Sept 20, 2013 Monica Arienzo

  3. Positive Feedback Negative Feedback

  4. Iron and the Biological Pump Why is this important?

  5. Iron and the Biological Pump • Hypothesis: Oceans are (for the most part) iron limited, therefore addition of iron leads to increased primary productivity • Requirements: • Iron limited to begin with • Iron must be bioavailable (depends on mineralogy) • The source of the iron (size distribution) • Duration of the iron source to ocean • Threshold concentration of iron in the ocean

  6. Iron and the Biological Pump • Hypothesis: Oceans are (for the most part) iron limited, therefore addition of iron leads to increased primary productivity • Requirements: • Iron limited to begin with • Iron must be bioavailable (depends on mineralogy) • The source of the iron (size distribution) • Duration of the iron source to ocean • Threshold concentration of iron in the ocean • Iron solubility is highly variable and should be considered in models • How do these requirements vary with changes to ocean chemistry (ie OA conditions)

  7. Dust and climate • Size: • Regional scale dust size invariance • Radiative: scattering vs absorption • Impacts of where on the earth (desert) • Cloud nuclei All are impacted by one or more: source, mineralogy, size, shape Scale up?

  8. Present

  9. LGM Scale is different

  10. LGM Dust • Equatorial Pacific: • Decreased dust W  E and South • Lack of Modern S. Hemisphere data = hard to interpret paleo record • Antarctica: Dusty, Patagonia major source ?

  11. LGM Dust • Expansion of dust sources • Equatorial Pacific: • Decreased dust W  E and South • Lack of Modern S. Hemisphere data = hard to interpret paleo record • Antarctica: Dusty, Patagonia major source ? • South Atlantic: S. American dust source • Paleoproductivity: increased during glacial with dust increase? Contradicting evidence? Is iron the only limiting nutrient? • Feedback on climate? • Millennial scale climate: dust peaks associate with H events and before D/O events, do these events feedback to the glacial climate?

  12. U-Th disequilibrium – 230Th/232Th U and Th chemically separate in aqueous solutions under oxidizing conditions: U+6 remains dissolved (UO22+) Oceanic residence time of ~ 400,000 y Th+4 is removed by scavenging Oceanic residence time of ~ 20 y Unsupported (excess) Th Deposition of Th = to supply rate

  13. U-Th disequilibrium – 230Th/232Th Total Th = Unsupported (excess) Th + Supported Th (from U decay) 0 • 230 - λt Step 1: Calculate the slope (m) Step 2: Calculate the accumulation rate (a) Step 3: Calculate deposition age at a given depth (h) Step 4: Use ThAxat (h) and initial ThAxto calculate age

  14. U-Th disequilibrium – 230Th/232Th: Example x 130 = -0.335

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