Bottom water warming in the North Pacific Ocean


Observations of changes in the properties of ocean waters have been restricted to surface1 or intermediate-depth waters2,3, because the detection of change in bottom water is extremely difficult owing to the small magnitude of the expected signals. Nevertheless, temporal changes in the properties of such deep waters across an ocean basin are of particular interest, as they can be used to constrain the transport of water at the bottom of the ocean and to detect changes in the global thermohaline circulation. Here we present a comparison of a trans-Pacific survey completed in 1985 (refs 4, 5) and its repetition in 1999 (ref. 6). We find that the deepest waters of the North Pacific Ocean have warmed significantly across the entire width of the ocean basin. Our observations imply that changes in water properties are now detectable in water masses that have long been insulated from heat exchange with the atmosphere.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Figure 1: The location of stations occupied for WHP Line P1 revisit in 1999.
Figure 2: The difference in potential temperature (a) and salinity (b) between the two surveys of line P1 in 1999 and 1985, plotted against depth.
Figure 3: The difference in salinity between 1999 and 1985 for line P1, as in Fig. 2b, but plotted with the density parameter σ4 as the vertical axis.
Figure 4: The difference in area between the 1999 and 1985 surveys in the areas along WHP Line P1 occupied by different potential temperatures.


  1. 1

    Levitus, S., Antonov, J. I., Boyer, T. P. & Stephens, C. Warming of the world ocean. Science 287, 2225–2229 (2000)

    ADS  CAS  Article  Google Scholar 

  2. 2

    Wong, A. P., Bindoff, N. L. & Church, J. A. Large–scale freshening of intermediate waters in the Pacific and Indian Oceans. Nature 400, 440–443 (1999)

    ADS  CAS  Article  Google Scholar 

  3. 3

    Roemmich, D. & Wunsch, C. Apparent changes in the climatic state of the deep North Atlantic Ocean. Nature 307, 447–450 (1984)

    ADS  Article  Google Scholar 

  4. 4

    Talley, L. D., Martin, M., Salameh, P. & the Oceanographic Data Facility. Transpacific Section in the Subpolar Gyre (TPS47): Physical, Chemical, and CTD Data, R/V Thomas Thompson TT190, 4 August 1985–7 September 1985 1–246 (Ref. 88–9, Scripps Inst. Of Oceanography, La Jolla, CA, 1988)

    Google Scholar 

  5. 5

    Talley, L. D., Joyce, T. & deSzoeke, R. A. Trans-Pacific sections at 47°N and 152°W: distribution of properties. Deep-Sea Res. (Suppl.) 38, S63–S82 (1991)

    ADS  Article  Google Scholar 

  6. 6

    Uchida, H., Fukasawa, M. & Freeland, H. J. WHP P01 Revisit Data Book 1–73 (Jamstec, Yokosuka, 2002)

    Google Scholar 

  7. 7

    Johnson, G. C., Rudnick, D. L. & Taft, B. A. Bottom water variability in the Samoa Passage. J. Mar. Res. 52, 177–195 (1994)

    Article  Google Scholar 

  8. 8

    Sclater, J. G. & Parsons, B. Oceans and continents: similarities and differences in the mechanisms of heat loss. J. Geophys. Res. 85, 11535–11552 (1981)

    ADS  Article  Google Scholar 

  9. 9

    Joyce, T. M., Warren, B. A. & Talley, L. D. The geothermal heating of the abyssal subarctic Pacific Ocean. Deep-Sea Res. 33, 1003–1005 (1986)

    ADS  CAS  Article  Google Scholar 

  10. 10

    Mantyla, A. & Reid, J. L. Abyssal characteristics of the world ocean waters. Deep-Sea Res. 30, 805–833 (1983)

    ADS  CAS  Article  Google Scholar 

  11. 11

    Johnson, G. C. & Orsi, A. H. Southwest Pacific water-mass exchanges between 1968/69 and 1990/91. J. Clim. 10, 306–316 (1997)

    ADS  Article  Google Scholar 

  12. 12

    Gille, S. H. Warming of the southern ocean since the 1950s. Science 295, 1275–1277 (2002)

    ADS  CAS  Article  Google Scholar 

  13. 13

    Preston-Thomas, H. The international temperature scale of 1990. Metrologia 27, 3–10 (1990)

    ADS  Article  Google Scholar 

  14. 14

    Mantyla, A. W. Standard seawater comparison updated. J. Phys. Oceanogr. 17, 543–548 (1987)

    ADS  Article  Google Scholar 

  15. 15

    Aoyama, M., Joyce, T., Kawano, T. & Takatsuki, Y. Standard seawater comparison up to P129. Deep-Sea Res. 49, 1103–1114 (2002)

    Article  Google Scholar 

  16. 16

    Kawano, T., Takatsuki, Y., Imai, J. & Aoyama, M. Seawater and quality evaluation of the standard seawater supplied in a bottle. [In Japanese with English abstract]. J. Jpn Soc. Mar. Surv. Tech. 13, 11–18 (2001)

    Google Scholar 

  17. 17

    Reid, J. L. On the total geostrophic circulation of the Pacific Ocean: flow patterns, tracers and transports. Prog. Oceanogr. 39, 263–352 (1997)

    ADS  Article  Google Scholar 

Download references


We thank the officers and crew of the three research vessels (RV Kaiyo-maru of JFA, RV Mirai of JAMSTEC, and CCGS John P. Tully) and all technical assistants. The Canadian contribution was funded by the Strategic Science Fund of the Department of Fisheries and Oceans, and the Japanese contributions were funded by the Promotional Foundation for Science and Technology of the Science and Technology Agency of Japan (now known as the Ministry of Education, Culture, Sports, Science and Technology).

Author information



Corresponding authors

Correspondence to Masao Fukasawa or Howard Freeland.

Ethics declarations

Competing interests

The authors declare that they have no competing financial interests.

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Fukasawa, M., Freeland, H., Perkin, R. et al. Bottom water warming in the North Pacific Ocean. Nature 427, 825–827 (2004).

Download citation

Further reading


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.