IPCC AR4 Chapter 5

1. Ocean temperature, salinity and oxygen changes in the Pacific and subtropical southern hemisphere Lynne Talley (ltalley@ucsd.edu) Scripps Institution of Oceanography, University of California San Diego 0.04 0.06 0.08 0.1 0.2 0 0.06 0.5 0.9 0.04 0.06 0.08 0.03 0.3 0.03 0.1 0.2 0 0.06 0.5 0.2 0.9 Temperature Salinity IPCC AR4 Chapter 5 Upper ocean (0-700 m), 50 year temperature trend Levitus et al. (2005) IPCC AR4 Chapter 5 Upper ocean (0-500 m), 50 year salinity Water column hydrography Boyer et al. (2005) Curry et al. (2003) & Wong et al. (2001) Pacific Atlantic Figure 5.2. Linear trends (1955–2003) of change in ocean heat content per unit surface area (W m–2) for the 0 to 700 m layer, based on the work of Levitus et al. (2005a). The linear trend is computed at each grid point using a least squares fit to the time series at each grid point. The contour interval is 0.25 W m–2. Red shading indicates values equal to or greater than 0.25 W m–2 and blue shading indicates values equal to or less than –0.25 W m–2. Figure 5.3. Linear trend (1955–2003) of zonally averaged temperature in the upper 1,500 m of the water column of the Atlantic, Pacific, Indian and World Oceans. The contour interval is 0.05°C per decade, and the dark solid line is the zero contour. Red shading indicates values equal to or greater than 0.025°C per decade and blue shading indicates values equal to or less than –0.025°C per decade. Based on the work of Levitus et al. (2005a). Figure 5.5: Linear trends (1955–1998) of zonally averaged salinity (psu) in the upper 500 m of the Atlantic, Pacific, Indian and World Oceans. The contour interval is 0.01 psu per decade and dashed contours are ±0.005 psu per decade. The dark solid line is the zero contour. Red shading indicates values equal to or greater than 0.005 psu per decade and blue shading indicates values equal to or less than –0.005 psu per decade. Based on the work of Boyer et al. (2005). Deep ocean warming based on repeat hydrography Johnson et al. (2009) Kawano et al. (2008) Salinity trend map (unpublished) (Boyer et al., personal communication) Figure 5.6. Meridional sections of differences in salinity (psu) of the a) Atlantic Ocean for the period 1985 to 1999 minus 1955 to 1969 and b) Pacific Ocean for the World Ocean Circulation Experiment (WOCE) 150°W section (1991–1992) and historical data from 1968 plus or minus 7.5 years.Contours are the mean salinity fields along each section and show the key features. The salinity differences are differences along isopycnals that have been mapped to pressure surfaces. The Atlantic section is along the western side of the Atlantic Ocean and the Pacific section is along 150°W. The two figures are redrafted from Curry et al. (2003) and Wong et al (2001).Water masses shown include Antarctic Intermediate Water (AAIW), Circumpolar Deep Water (CDW), North Atlantic Deep Water (NADW), Mediterranean Water (MW), Labrador Sea Water (LSW), Denmark Strait Overflow Water (DSOW) and North Pacific Intermediate Water NPIW). The areas shaded in grey represent the seafloor and oceanic crust. NADW AABW Upper ocean salinity changes into the 2000s Salinity changes Atlantic 25°W 2003 minus 1989 Nearly opposite in sign to previous decade (Curry, Wong), more confined to thermocline, not in AAIW or NPIW Note increased salinity in N. Atlantic Pacific 150°W 2006 minus 1991 Fraction of bottom water that is NADW and that is AABW (Johnson, 2008) Decadal heat content change in the Pacific Ocean (Kawano et al., 2008) Surface salinity 2005 (Argo) minus WOA01 climatology Surface salinity Hosoda et al.(2008) Heat content change (W/m2) (Johnson et al., 2009) • Warming of 0.1C over 13 years in SE Indian Ocean • Like local heat gain of 0.9 W m-2 below 3000 m • 4 cm sea level rise (with freshening) below 3000 • 0.04C over 16 years in SW Atlantic Ocean • 0.03C over 14 years in SE Pacific Ocean The deep ocean warming is GLOBAL Much (most ) for the bottom layer warming is from the Antarctic and not the North Atlantic Pacific warming is due to Antarctic changes, propagated as Kelvin/Rossby waves rather than advection (Kawano et al., 2008) Global 30°S subtropical gyre changes Salinity change: increased subduction (ventilation) North Pacific and tropical oxygen declines Oxygen change Chlorofluorocarbon change IPCC AR4 Chapter 5 Oxygen decline at base of pycnocline throughout subpolar and subtropical N. Pacific: reduced ventilation Deutsch et al. (2005) Oxygen change: increased ST thermocline ventilation Pacific Indian Atlantic Atlantic 2003 minus 1992 Indian: 2002 minus 1987 Pacific: 2003 minus 1991 Additional documentation of O2 decline (Mecking et al., 2008) Subtropical gyre intensification associated with increased Southern Annular Mode index (15-20% increase in circulation) Pacific: Roemmich et al. (JPO 2007) Indian: McDonagh et al. (J Clim 2005) Southern Annular Mode sea level pressure pattern Dyn. Ht. changes Argo minus WOCE Change in SLP and Ekman pumping SAM index 200/1800 1000/1800 Roemmich et al. (2007) Tropical oxygen minimum expanding Stramma et al. (Science, 2008)