projected changes to the tropical pacific ocean
DESCRIPTION
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. - PowerPoint PPT PresentationTRANSCRIPT
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Projected changes to the tropical Pacific Ocean
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Based on Chapters 3 & 4
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Outline
• Projected temperatures and currents: surface and vertical structure
• Implications for oceanic nutrients
• Acidification
• Food web for tuna
• Influence of temperature on tuna
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Change in SST °C (2000-2100)
• 2000: 27.4°C• 2035: 28.1°C (+0.7°C)• 2100: 29.9°C (+2.5°C)
Sea surface temperature
Ocean is heat sink!
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Thermocline depth
Vertical structure and stratification
Warm, mixed-layer
Cold, deep ocean
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Vertical structure and stratification
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• Most warming occurs at surface
• Leads to increase in stratification
Vertical structure and stratification
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Projected changes in vertical currents
Less downwelling
Less UPWELLINGLess downwelling
Less downwelling
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Implications for nutrients
• Thermocline acts as a barrier
• Limits the supply of nutrients
Warm, mixed-layer
Cold, deep ocean
Low nutrient
High nutrient
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Implications for nutrients
Increased stratification makes it harder to bring nutrients upwards
Warm, mixed-layer
Cold, deep ocean
Low nutrient
High nutrient
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Why is this important?
Nutrients support the food web for tuna
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Image: Marc Taquet, FADIO, IRD/IFREMER
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Projected changes in major currents
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Eddies
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Nutrient supply by eddies
•Eddies temporarily lift the nutrient-rich waters
•Eddy activity is related to current strengths
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Eddies and nutrients
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Convergence zone
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Similarities with ENSO
Skipjack tuna catch
Source: Lehodey et al. (1997)
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Ocean acidification
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Projected acidification
Saturation >4 healthy conditions
Saturation falls below 3.3 causing problems for some corals
Saturation decreases to 2.4
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Sea level rise
Projection 2035 2050 2100
IPCC 8 cm 18-38 cm 23-51 cm
Semi-empirical 20-30 cm 70-110 cm 90-140 cm
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Summary•I
ncreases 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