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Projected changes to the tropical Pacific Ocean

Projected changes to the tropical Pacific Ocean. Based on Chapters 3 & 4. Outline. Projected temperatures and currents: surface and vertical structure Implications for oceanic nutrients Acidification Food web for tuna Influence of temperature on tuna. Sea surface temperature.

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Projected changes to the tropical Pacific Ocean

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  1. Projected changes to the tropical Pacific Ocean

  2. Based on Chapters 3 & 4

  3. Outline • Projected temperatures and currents: surface and vertical structure • Implications for oceanic nutrients • Acidification • Food web for tuna • Influence of temperature on tuna

  4. Sea surface temperature Change in SST °C (2000-2100) • 2000: 27.4°C • 2035: 28.1°C (+0.7°C) • 2100: 29.9°C (+2.5°C) Ocean is heat sink!

  5. Vertical structure and stratification } Warm, mixed-layer } Thermocline depth } Cold, deepocean

  6. Vertical structure and stratification } } }

  7. Vertical structure and stratification • Most warmingoccurs at surface • Leads to increase in stratification

  8. Projected changes in vertical currents Less downwelling Less downwelling Less UPWELLING Less downwelling

  9. Implications for nutrients Warm, mixed-layer • Thermocline acts as a barrier • Limits the supply of nutrients Cold, deepocean Lownutrient High nutrient

  10. Implications for nutrients Warm, mixed-layer Cold, deepocean Lownutrient Increased stratification makes it harder to bring nutrients upwards High nutrient

  11. Why is this important? Nutrients support the food web for tuna

  12. Image: Marc Taquet, FADIO, IRD/IFREMER

  13. Projected changes in major currents

  14. Eddies

  15. Nutrient supply by eddies • Eddies temporarily lift the nutrient-rich waters • Eddy activity is related to current strengths

  16. Eddies and nutrients

  17. Convergence zone

  18. Similarities with ENSO • Skipjack tuna catch Source: Lehodey et al. (1997)

  19. Ocean acidification

  20. Projected acidification • Saturation >4 healthy conditions • Saturation falls below 3.3 causing problems for some corals • Saturation decreases to 2.4

  21. Sea level rise

  22. Summary • Increases in sea surface temperature • Stronger stratification • Nutrient supply reduced due to increase in stratification, with effects on tuna food web • Slowdown of equatorial currents and upwelling • Aragonite drops below critical levels • Sea level rise, > 1 m cannot be ruled out

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