Estimating Oceanic Heat Content Change Using Isotherms

Matthew D. Palmer Met Office Hadley Centre, Exeter, United Kingdom

Search for other papers by Matthew D. Palmer in
Current site
Google Scholar
PubMed
Close
and
Keith Haines Environmental Systems Science Centre, University of Reading, Reading, United Kingdom

Search for other papers by Keith Haines in
Current site
Google Scholar
PubMed
Close
Restricted access

Abstract

This paper presents a new analysis of ocean heat content changes over the last 50 yr using isotherms by calculating the mean temperature above the 14°C isotherm and the depth of the 14°C isotherm as separate variables. A new quantity called the “relative heat content” (“RHC”) is introduced, which represents the minimum local heat content change over time, relative to a fixed isotherm. It is shown how mean temperature and isotherm depth changes make separable and additive contributions to changes in RHC.

Maps of RHC change between 1970 and 2000 show similar spatial patterns to a traditional fixed-depth ocean heat content change to 220 m. However, the separate contributions to RHC suggest a more spatially uniform contribution from warming above the isotherm, while isotherm depth changes show wind-driven signals, of which some are identifiable as being related to the North Atlantic Oscillation. The time series show that the warming contribution to RHC dominates the global trend, while the depth contribution only dominates on the basin scale in the North Atlantic. The RHC shows minima associated with the major volcanic eruptions (particularly in the Indian Ocean), and these are entirely contributed by mean temperature changes rather than isotherm depth changes. The depth change contributions to RHC are strongly affected by the recently reported XBT fall-rate bias, whereas the mean temperature contributions are not. Therefore, only the isotherm depth change contributions to RHC will need to be reassessed as fall-rate-corrected data become available.

Corresponding author address: Dr. Matt Palmer, Met Office Hadley Centre, FitzRoy Road, Exeter, EX1 3PB, United Kingdom. Email: matthew.palmer@metoffice.gov.uk

Abstract

This paper presents a new analysis of ocean heat content changes over the last 50 yr using isotherms by calculating the mean temperature above the 14°C isotherm and the depth of the 14°C isotherm as separate variables. A new quantity called the “relative heat content” (“RHC”) is introduced, which represents the minimum local heat content change over time, relative to a fixed isotherm. It is shown how mean temperature and isotherm depth changes make separable and additive contributions to changes in RHC.

Maps of RHC change between 1970 and 2000 show similar spatial patterns to a traditional fixed-depth ocean heat content change to 220 m. However, the separate contributions to RHC suggest a more spatially uniform contribution from warming above the isotherm, while isotherm depth changes show wind-driven signals, of which some are identifiable as being related to the North Atlantic Oscillation. The time series show that the warming contribution to RHC dominates the global trend, while the depth contribution only dominates on the basin scale in the North Atlantic. The RHC shows minima associated with the major volcanic eruptions (particularly in the Indian Ocean), and these are entirely contributed by mean temperature changes rather than isotherm depth changes. The depth change contributions to RHC are strongly affected by the recently reported XBT fall-rate bias, whereas the mean temperature contributions are not. Therefore, only the isotherm depth change contributions to RHC will need to be reassessed as fall-rate-corrected data become available.

Corresponding author address: Dr. Matt Palmer, Met Office Hadley Centre, FitzRoy Road, Exeter, EX1 3PB, United Kingdom. Email: matthew.palmer@metoffice.gov.uk

Save
  • AchutaRao, K. M., B. D. Santer, P. J. Gleckler, K. E. Taylor, D. W. Pierce, T. P. Barnett, and T. M. L. Wigley, 2006: Variability of ocean heat uptake: Reconciling observations and models. J. Geophys. Res., 111 , C05019. doi:10.1029/2005JC003136.

    • Search Google Scholar
    • Export Citation
  • Bindoff, N. L., and T. J. McDougall, 1994: Diagnosing climate change and ocean ventilation using hydrographic data. J. Phys. Oceanogr., 24 , 11371152.

    • Search Google Scholar
    • Export Citation
  • Bindoff, N. L., and Coauthors, 2007: Observations: Oceanic climate change and sea level. Climate Change 2007: The Physical Science Basis, S. Solomon et al., Eds., Cambridge University Press, 385–432.

    • Search Google Scholar
    • Export Citation
  • Bond, N. A., J. E. Overland, M. Spillane, and P. Stabeno, 2003: Recent shifts in the state of the North Pacific. Geophys. Res. Lett., 30 , 2183. doi:10.1029/2003GL018597.

    • Search Google Scholar
    • Export Citation
  • Conkright, M. E., and Coauthors, 2002: Introduction. Vol. 1, World Ocean Database 2001, NOAA Atlas NESDID 42, 159 pp.

  • Davis, R. E., J. T. Sherman, and J. Dufour, 2001: Profiling ALACEs and other advances in autonomous subsurface floats. J. Atmos. Oceanic Technol., 18 , 982993.

    • Search Google Scholar
    • Export Citation
  • Dickson, R. R., 1999: All change in the Arctic. Nature, 397 , 389391.

  • Domingues, C. M., J. A. Church, N. J. White, P. J. Gleckler, S. E. Wijffels, P. M. Barker, and J. R. Dunn, 2008: Improved estimates of upper-ocean warming and multi-decadal sea-level rise. Nature, 453 , 10901094.

    • Search Google Scholar
    • Export Citation
  • Gille, S. T., 2008: Decadal-scale temperature trends in the Southern Hemisphere ocean. J. Climate, 21 , 47494765.

  • Gouretski, V., and K. P. Koltermann, 2007: How much is the ocean really warming? Geophys. Res. Lett., 34 , L01610. doi:10.1029/2006GL027834.

    • Search Google Scholar
    • Export Citation
  • Gregory, J. M., H. T. Banks, P. A. Stott, J. A. Lowe, and M. D. Palmer, 2004: Simulated and observed decadal variability in ocean heat content. Geophys. Res. Lett., 31 , L15312. doi:10.1029/2004/GL020258.

    • Search Google Scholar
    • Export Citation
  • Ingleby, B., and M. Huddleston, 2007: Quality control of ocean temperature and salinity profiles – Historical and real time data. J. Mar. Syst., 65 , 158175.

    • Search Google Scholar
    • Export Citation
  • Ishi, Y., and K. Hanawa, 2005: Large-scale variabilities of wintertime wind stress curl field in the North Pacific and their relation to atmospheric teleconnection patterns. Geophys. Res. Lett., 32 , L10607. doi:10.1029/2004GL022330.

    • Search Google Scholar
    • Export Citation
  • Ishii, M., and M. Kimoto, 2009: Reevaluation of historical ocean heat content variations with time-varying XBT and MBT depth bias corrections. J. Oceanogr., 65 , 287299.

    • Search Google Scholar
    • Export Citation
  • Ishii, M., M. Kimoto, and M. Kachi, 2003: Historical ocean subsurface temperature analysis with error estimates. Mon. Wea. Rev., 131 , 5173.

    • Search Google Scholar
    • Export Citation
  • Kiktev, D., D. M. H. Sexton, L. Alexander, and C. K. Folland, 2003: Comparison of modeled and observed trends in indices of daily climate extremes. J. Climate, 16 , 35603571.

    • Search Google Scholar
    • Export Citation
  • Knight, J. R., R. J. Allan, C. K. Folland, M. Vellinga, and M. E. Mann, 2005: A signature of persistent natural thermohaline circulation cycles in observed climate. Geophys. Res. Lett., 32 , L20708. doi:10.1029/2005GL024233.

    • Search Google Scholar
    • Export Citation
  • Knutti, R., and L. Tomassini, 2008: Constraints on the transient climate response from observed global temperature and ocean heat uptake. Geophys. Res. Lett., 35 , L09701. doi:10.1029/2007GL032904.

    • Search Google Scholar
    • Export Citation
  • Leadbetter, S. J., R. G. Williams, E. L. McDonagh, and B. A. King, 2007: A twenty year reversal in water mass trends in the subtropical North Atlantic. Geophys. Res. Lett., 34 , L12608. doi:10.1029/2007GL029957.

    • Search Google Scholar
    • Export Citation
  • Levitus, S., J. I. Antonov, T. P. Boyer, and C. Stephens, 2000: Warming of the World Ocean. Science, 287 , 22252229.

  • Levitus, S., J. I. Antonov, and T. P. Boyer, 2005: Warming of the world ocean, 1955-2003. Geophys. Res. Lett., 32 , L02604. doi:10.1029/2004GL021592.

    • Search Google Scholar
    • Export Citation
  • Levitus, S., J. I. Antonov, T. P. Boyer, R. A. Locarnini, H. E. Garcia, and A. V. Mishonov, 2009: Global ocean heat content 1955-2007 in light of recently revealed instrumentation problems. Geophys. Res. Lett., 36 , L07608. doi:10.1029/2008GL037155.

    • Search Google Scholar
    • Export Citation
  • Lozier, M. S., S. Leadbetter, R. G. Williams, V. Roussenov, M. S. Reed, and N. J. Moore, 2008: The spatial pattern and mechanisms of heat content change in the North Atlantic. Science, 319 , 800803.

    • Search Google Scholar
    • Export Citation
  • Lyman, J. M., and G. C. Johnson, 2008: Estimating annual global upper-ocean heat content anomalies despite irregular in situ ocean sampling. J. Climate, 21 , 56295641.

    • Search Google Scholar
    • Export Citation
  • Palmer, M. D., H. L. Bryden, J. Hirschi, and J. Marotzke, 2004: Observed changes in the South Indian Ocean gyre circulation, 1987-2002. Geophys. Res. Lett., 31 , L15303. doi:10.1029/2004GL020506.

    • Search Google Scholar
    • Export Citation
  • Palmer, M. D., K. Haines, S. F. B. Tett, and T. J. Ansell, 2007: Isolating the signal of ocean global warming. Geophys. Res. Lett., 34 , L23610. doi:10.1029/2007GL031712.

    • Search Google Scholar
    • Export Citation
  • Parker, D., C. Folland, A. Scaife, J. Knight, A. Colman, P. Baines, and B. Dong, 2007: Decadal to multidecadal variability and the climate change background. J. Geophys. Res., 112 , D18115. doi:10.1029/2007JD008411.

    • Search Google Scholar
    • Export Citation
  • Polyakov, I. V., U. S. Bhatt, H. L. Simmons, D. Walsh, J. E. Walsh, and X. Zhang, 2005: Multidecadal variability of North Atlantic temperature and salinity during the twentieth century. J. Climate, 18 , 45624581.

    • Search Google Scholar
    • Export Citation
  • Rayner, N. A., D. E. Parker, E. B. Horton, C. K. Folland, L. V. Alexander, D. P. Rowell, E. C. Kent, and A. Kaplan, 2003: Global analyses of sea surface temperature, sea ice, and night marine air temperature since the late nineteenth century. J. Geophys. Res., 108 , 4407. doi:10.1029/2002JD002670.

    • Search Google Scholar
    • Export Citation
  • Reseghetti, F., M. Borghini, and G. M. R. Manzella, 2006: Improved quality check procedures of XBT profiles in MFS-VOS. Ocean Sci. Discuss., 3 , 14411480.

    • Search Google Scholar
    • Export Citation
  • Roemmich, D., J. Gilson, R. Davis, P. Sutton, S. Wijffels, and S. Riser, 2007: Decadal spinup of the South Pacific subtropical gyre. J. Phys. Oceanogr., 37 , 162173.

    • Search Google Scholar
    • Export Citation
  • Stott, P. A., and C. E. Forest, 2007: Ensemble climate predictions using climate models and observational constraints. Philos. Trans. Roy. Soc. London, 365A , 20292052.

    • Search Google Scholar
    • Export Citation
  • Thorne, P. W., D. E. Parker, J. R. Christy, and C. A. Mears, 2005: Uncertainties in climate trends – Lessons from upper-air temperature records. Bull. Amer. Meteor. Soc., 86 , 14371442.

    • Search Google Scholar
    • Export Citation
  • Visbeck, M., E. Chassignet, R. Curry, T. Delworth, B. Dickson, and G. Krahmann, 2003: The ocean’s response to North Atlantic Oscillation variability. The North Atlantic Oscillation: Climatic Significance and Environmental Impact, Geophys. Monogr., Vol. 134, Amer. Geophys. Union, 113–146.

    • Search Google Scholar
    • Export Citation
  • Wijffels, S. E., J. Willis, C. M. Domingues, P. Baker, N. J. White, A. Gronell, K. Ridgway, and J. A. Church, 2008: Changing expendable bathythermograph fall rates and their impact on estimates of thermosteric sea level rise. J. Climate, 21 , 56575672.

    • Search Google Scholar
    • Export Citation
  • Wilks, D. S., 1997: Resampling hypothesis tests for autocorrelated fields. J. Climate, 10 , 6582.

  • Willis, J. K., D. Roemmich, and B. Cornuelle, 2004: Interannual variability in upper-ocean heat content, temperature and thermosteric expansion on global scales. J. Geophys. Res., 109 , C12036. doi:10.1029/2003JC002260.

    • Search Google Scholar
    • Export Citation
All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 506 111 9
PDF Downloads 291 83 6