1. Ocean Heat and Salt Content and its Impact on the Earth’s Climate System Tim Boyer Ocean Climate Lab/National Oceanographic Data Center Sep. 23, 2014

2. OUTLINE Climate Change Definition – Ocean’s Role in Climate Change Earth’s Heat Balance – Calculating Ocean Heat Content Time Series Gathering Data for Ocean Variability Studies – Ocean Observing Systems Ocean Heat Content Calculations – Upper and Lower Ocean Add the Salt – the Earth’s Freshwater Cycle Heat and Salt together – Sea level change Regional Study – Bay of Bengal Sea level Global warming hiatus – the Oceans role

3. Climate change definition Climate change refers to a statistically significant variation in either the mean state of the climate or in its variability, persisting for an extended period (typically decades or longer). Climate change may be due to natural internal processes or external forcings, or to persistent anthropogenic changes in the composition of the atmosphere or in land use. International Panel on Climate Change (IPCC) http://www.ipcc.ch/ipccreports/tar/ wg1/518.htm Figure from http://www.ipcc.ch/report/ar5/

4. Climate change and the collapse of the Akkadian empire: Evidence from the deep sea. Cullen et al., 2000. 6,000 years ago, increased aridity in Mesopotamia helped cause large social change Figure from http://www.ldeo.columbia.edu/res/div/ocp/arch/examples.shtml

5. (Feely, 2008, in BAMS) The Oceans Role: CO 2 sink

6. 6 Gulf of Mexico Hypoxia Watch (from 2006) The Oceans Role Low Oxygen Zones

7. 7 The Oceans Role Rossby, C. (1959), Current problems in meteorology, in The Atmosphere and Sea in Motion, pp. 9-50, Rockefeller Institute Press, New York. Based on the physical properties of water and the mass of the world ocean suggested the world ocean may play a dominant role in the earth’s heat balance on time-scales > interannual. Figure from http://content.time.com/time/covers/0,16641,19561217,00.html

8. 8 Rossby (1959) (1) “The role of the sea as a secular heat reservoir assumes quite a different character at the moment that one takes up the question of secular changes of the total heat balance, taking into account the circulation of the deeper layers. An elementary calculation gives the result that even as much as 1 % of the total incoming heat radiation could be stored in a layer of 1000 m thickness in the interior of the sea, without producing a temperature increase greater than 0.015°C per year. ”

9. 9 Rossby (1959) (2) “The assumption that our planet as a whole stands in firm radiation balance with outer space cannot be accepted without reservations, even if periods of several decades are taken into account.” “Anomalies in heat probably can be stored and temporarily isolated in the sea and after periods of the order of a few decades to a few centuries again influence the heat and water vapour exchange with the atmosphere.”

10. 10 Rossby Summary Cannot assume the Earth is in radiation balance with outer space The ocean has a huge potential as a heat reservoir The ocean may moderate the effects of a radiation imbalance, storing excess heat for decades or centuries

11. Hartmann, D.L., A.M.G. Klein Tank, M. Rusticucci, L.V. Alexander, S. Brönnimann, Y. Charabi, F.J. Dentener, E.J. Dlugokencky, D.R. Easterling, A. Kaplan, B.J. Soden, P.W. Thorne, M. Wild and P.M. Zhai, 2013: Observations: Atmosphere and Surface. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, pp. 159–254, doi:10.1017/CBO9781107415324.008 Figure 2.11: | Global mean energy budget under present-day climate conditions. Numbers state magnitudes of the individual energy fluxes in W m–2, adjusted within their uncertainty ranges to close the energy budgets. Numbers in parentheses attached to the energy fluxes cover the range of values in line with observational constraints. (Adapted from Wild et al., 2013.)

12. Hartmann, D.L., A.M.G. Klein Tank, M. Rusticucci, L.V. Alexander, S. Brönnimann, Y. Charabi, F.J. Dentener, E.J. Dlugokencky, D.R. Easterling, A. Kaplan, B.J. Soden, P.W. Thorne, M. Wild and P.M. Zhai, 2013: Observations: Atmosphere and Surface. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, pp. 159–254, doi:10.1017/CBO9781107415324.008 Figure 2.11: | Global mean energy budget under present-day climate conditions. Numbers state magnitudes of the individual energy fluxes in W m–2, adjusted within their uncertainty ranges to close the energy budgets. Numbers in parentheses attached to the energy fluxes cover the range of values in line with observational constraints. (Adapted from Wild et al., 2013.)

13. 13 Changes in Earth’s Heat Balance Components (10 22 J) During 1955-2003 (from Levitus, Antonov and Boyer, 2005, GRL) 83% or 0.5 W/m 2

14. How is Ocean Heat Content Changing? How do we reliably estimate the change? Levitus, S., et al. (2012), World ocean heat content and thermosteric sea level change (0–2000 m), 1955–2010, Geophys. Res. Lett., 39, L10603, doi:10.1029/2012GL0511010.1029/2012GL05110

15. 15 Global zonal average surface temperature anomaly (°K), 1890-1997 (Delworth and Knutson, 2000)

16. Gouretski, V., J. Kennedy, T. Boyer, and A. Köhl (2012), Consistent near-surface ocean warming since 1900 in two largely independent observing networks, Geophys. Res. Lett., 39, L19606, doi:10.1029/2012GL05297510.1029/2012GL052975 Difficult to Assess Historical Ocean Subsurface Warming

17. 17 Heat content equation for a water column A = area of ODSQ ρ = density of seawater C p = specific heat of seawater ΔT = temperature anomaly dz = thickness of the vertical layer of integration For each standard depth level temperature value in a T profile, we subtract the climatological mean to create an anomaly profile. We then compute anomalies by one-degree squares at each standard depth level and perform an objective analysis of each level. A

18. 18 World Ocean Database (WOD) A quality controlled collection of ocean profiles, plankton tow, and ship-based surface measurements from 1772-present.

19. World Ocean Database by Instrument Type 19

20. (1a) OSD: 2,530,868 profiles (1b) MBT: 2,427,277 profiles (1c) XBT: 2,109,400 profiles (1d) CTD: 634,976 profiles (1e) UOR: 88,184 profiles (1f) PFL: 520,816 profiles (1g) MRB: 566,540 profiles (1h) DRB: 122,226 profiles (1i) APB: 89,558 profiles (1j) GLD: 5,857 profiles (1k) SUR: 9,178 profiles (1l) Plankton: 230,944 profiles World Ocean Database: World’s largest publicly available oceanographic profile database

21. 21 Data from international projects Left: GEOSECS bottle and CTD data (1972-1979) Right: WOCE CTD data (1990-1998)

22. 22 Data from universities, fisheries Left: Bottle data from Hokkaido University (Japan) (1962-1994) Right: Temperature Data from US National Marine Fisheries (1964-1997)

23. 23 Data Archeology and Rescue Cruise Reports found: Red/Yellow: Library of University of Tromso, Norway Blue: Public Library, St. Petersburg, Russia Green: Public Library, New York City, USA (in part)

24. 24 Gulf of Mexico Estuarine Inventory (1967- 68)

25. 1934 : Nansen Cast Temperature Data During Peek of Different Observing Systems Red=Nansen Cast /CTD[1890s/1964] Light Blue=MBT [1939] Dark Blue=XBT [1967] Green=Argo float [2001] Orange=Tropical buoy [1984] 25 Abraham, J. P., M. Baringer, N. L. Bindoff, T. Boyer, L. J. Cheng, J. A. Church, J. L. Conroy, C. M. Domingues, J. T. Fasullo, J. Gilson, G. Goni, S. A. Good, J. M. Gorman, V. Gouretski, M. Ishii, G. C. Johnson, S. Kizu, J. M. Lyman, A. M. Macdonald, W. J. Minkowycz, S. E. Moffitt, M. Palmer, A. Piola, F. Reseghetti, K. E. Trenberth, I. Velicogna, S. E. Wijffels, J. K. Willis: Monitoring systems of global ocean heat content and the implications for climate change, a review. - Review of Geophysics, Vol. 51, pp 450-483

26. 1934 : Nansen Cast 1960 : MBT Temperature Data During Peak of Different Observing Systems Red=Nansen Cast /CTD[1890s/1964] Light Blue=MBT [1939] Dark Blue=XBT [1967] Green=Argo float [2001] Orange=Tropical buoy [1984] 26 Abraham, J. P., M. Baringer, N. L. Bindoff, T. Boyer, L. J. Cheng, J. A. Church, J. L. Conroy, C. M. Domingues, J. T. Fasullo, J. Gilson, G. Goni, S. A. Good, J. M. Gorman, V. Gouretski, M. Ishii, G. C. Johnson, S. Kizu, J. M. Lyman, A. M. Macdonald, W. J. Minkowycz, S. E. Moffitt, M. Palmer, A. Piola, F. Reseghetti, K. E. Trenberth, I. Velicogna, S. E. Wijffels, J. K. Willis: Monitoring systems of global ocean heat content and the implications for climate change, a review. - Review of Geophysics, Vol. 51, pp 450-483

27. 1934 : Nansen Cast 1960 : MBT 1985 : XBT Temperature Data During Peak of Different Observing Systems Red=Nansen Cast /CTD[1890s/1964] Light Blue=MBT [1939] Dark Blue=XBT [1967] Green=Argo float [2001] Orange=Tropical buoy [1984] 27 Abraham, J. P., M. Baringer, N. L. Bindoff, T. Boyer, L. J. Cheng, J. A. Church, J. L. Conroy, C. M. Domingues, J. T. Fasullo, J. Gilson, G. Goni, S. A. Good, J. M. Gorman, V. Gouretski, M. Ishii, G. C. Johnson, S. Kizu, J. M. Lyman, A. M. Macdonald, W. J. Minkowycz, S. E. Moffitt, M. Palmer, A. Piola, F. Reseghetti, K. E. Trenberth, I. Velicogna, S. E. Wijffels, J. K. Willis: Monitoring systems of global ocean heat content and the implications for climate change, a review. - Review of Geophysics, Vol. 51, pp 450-483

28. 1934 : Nansen Cast 1960 : MBT 1985 : XBT 2009 : Argo Temperature Data During Peak of Different Observing Systems Red=Nansen Cast /CTD[1890s/1964] Light Blue=MBT [1939] Dark Blue=XBT [1967] Green=Argo float [2001] Orange=Tropical buoy [1984] 28 Abraham, J. P., M. Baringer, N. L. Bindoff, T. Boyer, L. J. Cheng, J. A. Church, J. L. Conroy, C. M. Domingues, J. T. Fasullo, J. Gilson, G. Goni, S. A. Good, J. M. Gorman, V. Gouretski, M. Ishii, G. C. Johnson, S. Kizu, J. M. Lyman, A. M. Macdonald, W. J. Minkowycz, S. E. Moffitt, M. Palmer, A. Piola, F. Reseghetti, K. E. Trenberth, I. Velicogna, S. E. Wijffels, J. K. Willis: Monitoring systems of global ocean heat content and the implications for climate change, a review. - Review of Geophysics, Vol. 51, pp 450-483

29. Levitus, S., et al. (2012), World ocean heat content and thermosteric sea level change (0–2000 m), 1955–2010, Geophys. Res. Lett., 39, L10603, doi:10.1029/2012GL0511010.1029/2012GL05110

30. 30 Measurements vs. Depth WOD13 Measurements (X10 5 )Measurements (X10 4 ) Depth (m)

31. Sarah G. Purkey and Gregory C. Johnson, 2010: Warming of Global Abyssal and Deep Southern Ocean Waters between the 1990s and 2000s: Contributions to Global Heat and Sea Level Rise Budgets*. J. Climate, 23, 6336–6351. doi: http://dx.doi.org/10.1175/2010JCLI3682.1http://dx.doi.org/10.1175/2010JCLI3682.1 Mean local heat fluxes (a) and thermosteric sea level (b) through 4000 m implied by abyssal warming below 4000 m from the 1990s to the 2000s

32. Deep Argo deployed in the Pacific June 16, 2014 http://cpo.noaa.gov/Home/AllNews/TabId/315/ArtMID/668/ArticleID/72606/Deep-Argo-floats-deployed-in-Pacific.aspx

33. The Global Water Cycle From The Global Water Cycle – Revising the Historical Representation: R. Schmitt http://www.whoi.edu/sbl/liteSite.do?litesiteid=18912&articleId=28329

34. The Global Water Cycle An Oceanographers View From The Global Water Cycle – Revising the Historical Representation: R. Schmitt http://www.whoi.edu/sbl/liteSite.do?litesiteid=18912&articleId=28329

35. Water Cycle Intensification: The salty getting saltier, the fresh getting fresher

37. 37 Sea level anomaly in the subpolar North Atlantic + GIN Seas (50°N-66°N) from in situ temperature and salinity profiles (0-2000 meters)

38. top) Equivalent freshwater content (red) and heat content (blue) in the subpolar North Atlantic and GIN Seas 0–2,000 meters (1955–1959) to (2002–2006). (bottom) Equivalent freshwater content (red) and heat content (blue) for the North Atlantic (0–80°N) 0–2,000 meters (1955–1959) to (2002–2006) with error estimates (2 × standard error). Boyer, T., S. Levitus, J. Antonov, R. Locarnini, A. Mishonov, H. Garcia, and S. A. Josey (2007), Changes in freshwater content in the North Atlantic Ocean 1955–2006, Geophys. Res. Lett., 34, L16603, doi:10.1029/2007GL030126.10.1029/2007GL030126

39. Boening, C., J. K. Willis, F. W. Landerer, R. S. Nerem, and J. Fasullo (2012), The 2011 La Niña: So strong, the oceans fell, Geophys. Res. Lett., 39, L19602, doi:10.1029/2012GL053055.10.1029/2012GL053055 Sea Level measured from altimeter = steric change + mass change Steric Change = Thermosteric + Halosteric components Mass Change = addition/subtraction of fresh water

40. V. V Gopalakrishna, T. Boyer, S. Siva Reddy, TVS Udaya Bhaksar, N. Kurian, J. Antonov, H. Rahman, M. Ravichandran, K. V. Subba Rao, A. Naik Examining Climate Change in the Bay of Bengal using a Combined Ocean Observing System

41. SST 1900-1997 vs. Cyclone frequency in the Bay of Bengal. Data from the India Meteorological Department. Cyclone Heat Source is the Upper Ocean Why isn’t cyclone frequency increasing?

44. SSH anomaly 1993 – 2007 for the Indian Ocean (from altimeter). Despite large increases in the Southern Indian Ocean, the Northern Indian SSH anomaly is close to or less than 0 mm. SSH anomaly in the Bay Of Bengal 1997-2000 showing significant decreasing SSH. SSH anomaly in the Bay of Bengal 2005-2008 showing Increases in SSH except in the west central Bay.

45. “…the rate of warming over the past 15 years (1998–2012; 0.05 [–0.05 to +0.15] °C per decade), which begins with a strong El Niño, is smaller than the rate calculated since 1951 (1951–2012; 0.12 [0.08 to 0.14] °C per decade). Trends for 15-year periods starting in 1995, 1996, and 1997 are 0.13 [0.02 to 0.24], 0.14 [0.03 to 0.24] and 0.07 [–0.02 to 0.18], respectively.” Hartmann, D.L., A.M.G. Klein Tank, M. Rusticucci, L.V. Alexander, S. Brönnimann, Y. Charabi, F.J. Dentener, E.J. Dlugokencky, D.R. Easterling, A. Kaplan, B.J. Soden, P.W. Thorne, M. Wild and P.M. Zhai, 2013: Observations: Atmosphere and Surface. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, pp. 159–254, doi:10.1017/CBO9781107415324.008. Atmospheric Global Warming Hiatus?

46. Chen, X. and Tung, K. (2014), Varying planetary heat sink led to global-warming slowdown and acceleration Science, 345 (6199), 897-903. [DOI:10.1126/science.1254937] Increased depth penetration of heat in ocean related to increased salinity in the subpolar North Atlantic Global Warming Hiatus Cause ?

47. Atlantic Multidecadal Oscillation Principal Component time series Nigam, S., B. Guan, and A. Ruiz-Barradas (2011), Key role of the Atlantic Multidecadal Oscillation in 20th century drought and wet periods over the Great Plains, Geophys. Res. Lett., 38, L16713 Pacific Decadal Oscillation Index Time Series http://www.jisao.washington.edu/pdo/http://www.jisao.washington.edu/pdo/ data from N. Mantua) Coincidental cool phase AMO + PDO Nigam et al. submitted

48. Summary Large majority of excess heat in Earth’s system is sequestered in the ocean The Ocean is the major component of the Earth’s freshwater cycle Historical data for ocean change studies is difficult to aggregate – better coverage at present and into the future Speculation: the lack of correspondence between sea level rise and sea surface temperature rise in the Bay of Bengal is due to subsurface cooling Global warming hiatus – deep ocean sink as main reason or one aspect of a complicated systemic adjustment? Regional Study – Bay of Bengal Sea level Global warming hiatus – the Oceans role