Post on 07-Jan-2016
description
transcript
Projected changes to the tropical Pacific Ocean
Based on.....
Outline
• Projected temperatures and currents: surface and vertical structure
• Implications for oceanic nutrients
• Ocean acidification
• Sea-level rise
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
The ocean is a heat sink!
Thermocline depth
Vertical structure and stratification
Warm, mixed-layer
Cold, deep ocean
}}
}
Thermocline depth
Vertical structure and stratification
Warm, mixed-layer
Cold, deep ocean
}}
}
• Most warming occurs at surface
• Leads to increase in stratification
Vertical structure and stratification
Projected changes in vertical currents
Less downwelling
Less UPWELLING
Less downwelling
Less downwelling
Implications for nutrients
• Thermocline acts as a barrier
• Limits the supply of nutrients
Warm, mixed-layer
Cold, deep ocean
Low nutrient
High nutrient
Implications for nutrients
•Increased stratification makes it harder to bring nutrients upwards
Warm, mixed-layer
Cold, deep ocean
Low nutrient
High nutrient
Why is this important?
• Nutrients support the food web for tuna
Projected changes in major currents
Eddies
Nutrient supply by eddies
• Eddies can temporarily lift nutrient-rich waters
• Eddy activity is related to current strength
Eddies and nutrients
Convergence zone
Importance of ENSO for fisheries
Skipjack tuna catch
Source: Lehodey et al. (1997)
Ocean acidification
Projected acidification
Saturation >4 = healthy conditions
Saturation falls below 3.3, causing problems for corals
Saturation decreases to 2.4
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
Summary
• Increases in sea surface temperature
• Stronger stratification
• Nutrient reduced due to increase in stratification
• Slowdown of equatorial currents and upwelling
• Aragonite drops below critical levels
• Sea level rise, > 1 m cannot be ruled out