Tracing the upper ocean’s“missing heat”A pause in the rise inupper ocean heat content:how unusual is it, and where did the...
A warming climateincreasing greenhouse gas concentrations affectthe Earth’s energy budget                                 ...
Observed ocean heat uptake           Levitus et al 2009                                Argo float program                 ...
International Argo float networkFebruary 2012 - 3500 active floats   NL = 37
Observed ocean heat uptake           Levitus et al 20090-700 m, global meanocean heat content                             ...
observations – surface       year=2000© National Oceanographic Data Center (NODC), USA
observations – 1000 m depth       year=2000© National Oceanographic Data Center (NODC), USA
observations – 1000 m depth       year=1980© National Oceanographic Data Center (NODC), USA
observations – 1000 m depth       year=1960© National Oceanographic Data Center (NODC), USA
Upper ocean heat uptake                      upper ocean has not                      gained heat since 20030-700 m global...
Upper ocean heat uptake                               “missing heat”                               ~ 0.3 · 1022 J/yr1. How...
Upper ocean heat uptake                                  “missing heat”                                  ~ 0.3 · 1022 J/yr...
the ESSENCE ensemble 17 coupled climate   model simulations   for 1950-2100 A1B emission scenario started from slightly   ...
the ESSENCE ensemble17 coupled climate  model simulations  for 1950-2100analysis of Ocean Heat ContentOHC =  ρ cp Tocea...
Upper OHC in ESSENCE                     forced trendOHC anomaly 0-700m
Upper OHC in ESSENCE                       forced trend                     measure for rangeOHC anomaly 0-700m   of natur...
Upper OHC in ESSENCEobservations                          forced trend                        measure for range   OHC anom...
Upper OHC in ESSENCE                                      mean trend 1969-2000   long-term ESSENCE trends are in agreemen...
Upper OHC in ESSENCE   OHC anomaly 0-700mcalculate 8-yr trends
Upper OHC in ESSENCE                        for each simulation                        for a 31-year period               ...
distribution of 8-yr trends in UOHC        model: 31 yrs x 17 = 527 events
distribution of 8-yr trends in UOHC               3% of               distribution25-30% chance of one or more (overlappin...
Where did the heat go?      space                   missing heat                              8 yr x 0.3 1022 J/yr =2.4·10...
Where did the heat go?               missing heat = 2.4·1022 J               atmosphere                takes much less en...
Where did the heat go?                           missing heat = 2.4·1022 J                           continents           ...
Where did the heat go?                missing heat = 2.4·1022 J                cryosphere [warming]                  take...
Where did the heat go?                missing heat = 2.4·1022 J                cryosphere                  melt 7.3 ·1016...
Where did the heat go?   space       missing heat               8 yr x 0.3 1022 J/yr =2.4·1022 J                  radiati...
Where did the heat go?   space       missing heat               8 yr x 0.3 1022 J/yr =2.4·1022 J                  radiati...
Top of the Atmosphere (TOA) Radiation 45% of the variation in upper OHC is associated with     a variation in the net outg...
Top of the Atmosphere (TOA) RadiationCAUSE: changes in cloud cover and heat uptake associated  with El Nino / La Nina even...
Deep Ocean Heat Content     35% of the decrease in upper OHC (0-700 m)is associated with an increase in deep OHC (700-3000...
Deep Ocean Heat Content              UOHC trend as function of depth
Deep Ocean Heat Content                        UOHC trend as function of depthdeep ocean convectionmixing of surface andsu...
Summary   A pause in the rise in upper Ocean Heat Content as    recently observed is not unusual in the late 20th /    ea...
Summary   A pause in the rise in upper Ocean Heat Content as    recently observed is not unusual in the late 20th /    ea...
Latest ocean heat content observations                Katsman and van Oldenborgh (2011)
Latest ocean heat content observations     ocean expansion is projected to result in     10-30 cm global mean sea level ri...
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Tracing the upper ocean’s “missing heat”

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Presentation given by Caroline Katsman at the symposium on Sea Level Rise by TU Delft Climate Institute http://bit.ly/Y5dPvY

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Tracing the upper ocean’s “missing heat”

  1. 1. Tracing the upper ocean’s“missing heat”A pause in the rise inupper ocean heat content:how unusual is it, and where did the heat go?Caroline KatsmanGeert Jan van Oldenborgh Royal Netherlands Meteorological Institute KNMI - Global Climate Division Caroline.Katsman@knmi.nl
  2. 2. A warming climateincreasing greenhouse gas concentrations affectthe Earth’s energy budget ocean expansion is responsible for ±50% of the observed global mean sea level rise [3 mm/yr over 1993-2003]% energy content change[1993-2003, data source: IPCC (2007)]
  3. 3. Observed ocean heat uptake Levitus et al 2009 Argo float program (2000-present)0-700 m, global meanocean heat content
  4. 4. International Argo float networkFebruary 2012 - 3500 active floats NL = 37
  5. 5. Observed ocean heat uptake Levitus et al 20090-700 m, global meanocean heat content eXpendable BathyThermographs (XBTs) – from moving ships
  6. 6. observations – surface year=2000© National Oceanographic Data Center (NODC), USA
  7. 7. observations – 1000 m depth year=2000© National Oceanographic Data Center (NODC), USA
  8. 8. observations – 1000 m depth year=1980© National Oceanographic Data Center (NODC), USA
  9. 9. observations – 1000 m depth year=1960© National Oceanographic Data Center (NODC), USA
  10. 10. Upper ocean heat uptake upper ocean has not gained heat since 20030-700 m global mean
  11. 11. Upper ocean heat uptake “missing heat” ~ 0.3 · 1022 J/yr1. How unusual is this, in light of the ongoing greenhouse gas forcing?2. Where did the energy go?
  12. 12. Upper ocean heat uptake “missing heat” ~ 0.3 · 1022 J/yr energy budget change of ~ 0.2 W / m2– the imbalance in the Earth’s energy budget due to greenhousegas forcing is ~0.85 ±0.15 W/m2 [Hansen et al 2005]–satellites measure incoming shortwave radiation and outgoinglongwave radiation at ~0.5 to 1.0 W/m2 precision [Trenberth et al 2010]
  13. 13. the ESSENCE ensemble 17 coupled climate model simulations for 1950-2100 A1B emission scenario started from slightly different initial conditions→ natural variabilityversus forced trends
  14. 14. the ESSENCE ensemble17 coupled climate model simulations for 1950-2100analysis of Ocean Heat ContentOHC =  ρ cp Tocean dAocean dzthe large amount of data allows for a statistically robust analysis of events and processes involved
  15. 15. Upper OHC in ESSENCE forced trendOHC anomaly 0-700m
  16. 16. Upper OHC in ESSENCE forced trend measure for rangeOHC anomaly 0-700m of natural variability
  17. 17. Upper OHC in ESSENCEobservations forced trend measure for range OHC anomaly 0-700m of natural variability
  18. 18. Upper OHC in ESSENCE mean trend 1969-2000 long-term ESSENCE trends are in agreement with observation-based estimates variability model simulations encompasses observations
  19. 19. Upper OHC in ESSENCE OHC anomaly 0-700mcalculate 8-yr trends
  20. 20. Upper OHC in ESSENCE for each simulation for a 31-year period → distribution OHC anomaly 0-700mcalculate 8-yr trends
  21. 21. distribution of 8-yr trends in UOHC model: 31 yrs x 17 = 527 events
  22. 22. distribution of 8-yr trends in UOHC 3% of distribution25-30% chance of one or more (overlapping) 8-yr periods with a negative trend in upper ocean heat content
  23. 23. Where did the heat go? space missing heat 8 yr x 0.3 1022 J/yr =2.4·1022 J atmosphere if absorbed in the ocean then ΔTocean ≈ +0.02 K cryosphere  atmosphereupper ocean continents continents   cryosphere  radiation to space deep ocean  deep ocean
  24. 24. Where did the heat go? missing heat = 2.4·1022 J atmosphere  takes much less energy toatmosphere warm one m3 of air (vol. heat capacity x 3000)  larger volume (x 20)upper ocean  ΔTatm ≈ +4.8 K
  25. 25. Where did the heat go? missing heat = 2.4·1022 J continents  takes 40% less energy to warm one m3 of rock (vol. heat capacity x 0.6)  heat penetrates only over ~50m in a few yearsupper ocean continents  ΔTland ≈ +1.2 K (upper 50m)
  26. 26. Where did the heat go? missing heat = 2.4·1022 J cryosphere [warming]  takes half the energy to cryosphere warm one m3 of ice (vol. heat capacity x 0.5)  volume of the ice sheets over which heat can beupper ocean absorbed is much smaller  ΔTice ≈ +7.5 K (upper 100m)
  27. 27. Where did the heat go? missing heat = 2.4·1022 J cryosphere  melt 7.3 ·1016 kg ice cryosphere  global mean SLR ≈ +0.2m (x 8 observed)upper ocean  3 x current sea ice extent Arctic Ocean
  28. 28. Where did the heat go? space missing heat 8 yr x 0.3 1022 J/yr =2.4·1022 J  radiation to space  deep ocean plateau in upper OHC: ⇔ downward trend superposed on longterm upward trendupper ocean ⇔ 8-yr trends with respect to the longterm trenddeep ocean
  29. 29. Where did the heat go? space missing heat 8 yr x 0.3 1022 J/yr =2.4·1022 J  radiation to space  deep ocean plateau in upper OHC ⇔ downward trend superposed on longterm upward trendupper ocean ⇔ 8-yr trends with respect to the longterm trenddeep ocean period 1990-2020
  30. 30. Top of the Atmosphere (TOA) Radiation 45% of the variation in upper OHC is associated with a variation in the net outgoing TOA radiation upper ocean cooling ⇔ more radiation out
  31. 31. Top of the Atmosphere (TOA) RadiationCAUSE: changes in cloud cover and heat uptake associated with El Nino / La Nina events (Pacific Ocean)
  32. 32. Deep Ocean Heat Content 35% of the decrease in upper OHC (0-700 m)is associated with an increase in deep OHC (700-3000 m)
  33. 33. Deep Ocean Heat Content UOHC trend as function of depth
  34. 34. Deep Ocean Heat Content UOHC trend as function of depthdeep ocean convectionmixing of surface andsubsurface watersdown to 1000-2000 m[variable process]
  35. 35. Summary A pause in the rise in upper Ocean Heat Content as recently observed is not unusual in the late 20th / early 21st century, despite greenhouse gas forcing Such a pause is associated with increased radiation to space (~45%) and an increase in the deep ocean heat content (~35%) The causes for these energy exchanges are two modes of natural variability (ENSO conditions and deep convection in the North Atlantic Ocean)
  36. 36. Summary A pause in the rise in upper Ocean Heat Content as recently observed is not unusual in the late 20th / early 21st century, despite greenhouse gas forcing Such a pause is associated with increased radiation to space (~45%) and an increase in the deep ocean heat content (~35%) The causes for these energy exchanges are two modes of natural variability (ENSO conditions and deep convection in the North Atlantic Ocean) Katsman and van Oldenborgh (2011)
  37. 37. Latest ocean heat content observations Katsman and van Oldenborgh (2011)
  38. 38. Latest ocean heat content observations ocean expansion is projected to result in 10-30 cm global mean sea level rise by the end of the century
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