Observations: Ocean Climate Change

• Changes in Global-Scale Temperature and Heat Content
• Large increase in ocean heat content over last 50 years
• Estimate for 0-700m layer is 10.9 X 10²² J (0.14 W m^-2
• Accounts for more than 90% of increase in heat content in earth system
• Average temperature increase for whole layer of more than 0.1^o
• Warming is greatest in Atlantic (about half of global total)
• Trends in North Pacific dominated by 1976 switch in PDO
• Strongest trends in the upper oceans
• Global-Scale changes in salinity
• Generally increasing in tropics, decreasing in high-latitudes, especially in Atlantic
• Imply stronger hydrologic cycle and poleward atmospheric moisture transport
• Pacific shows decreasing trend
• Biogeochemical Changes
• Increase in dissolved CO₂ leads to decrease in pH (acidification)
• Most anthropogenic carbon still concentrated in upper layers
• Changes in Sea Level
• Estimates from tide gauges give increase of about 1.7 mm/yr over last century
• Satellite altimetry estimates show increase of 3 mm/yr over last decade
• Spatial patterns of trends result from combination of heating and dynamical effects
• Strong ENSO signal at tropical Pacific island station
• Roughly 1/3-1/2 of sea level rise due to thermal expansion of sea water
• Largest contributor to recent rises
• Budget of global sea level rise not well determined