The events put forth in the Pentagon Report are a plausible scenario, although many scientists contest the events as something which is not likely to happen in the near future. There is every possibility though that if climate change continues due to global warming then at some point in the near future ocean currents may become affected in such a way as to stop. References

Bryden, H.L., Longworth, H.R. And Cunningham, S.A. (2005) Slowing of the Atlantic meridional overturning circulation at 25°N. Nature, 438, 655-665.

Danovaro, R., Dell'Anno, a., Fabiano, M., Pusceddu, a. And Tselepides, a. (2001) Deep-sea ecosystem response to climate changes: the eastern Mediterranean case study. Trends in Ecology and Evolution, 16(9), 505-510.

And Rhines, P.B. (2004) Decline of subpolar North Atlantic circulation during the 1990s. Science, 304(5670), 555-559.
Loder, J., Yashayaev, I. And Geshelin, Y. (2006) Water masses and currents in Orphan Basin of the North Atlantic. EOS Trans. AGU, 87(52) Suppl., AGU Fall Meeting.

Lutjeharms, J.R.E. And Ruijter, W.P.M. (1996) the influence of the Agulhas Current on the adjacent coastal ocean: possible impacts of climate change. Journal of Marine Systems, 7, 321-336.

McManus, J. (2006) the Once and Future Circulation of the Ocean. Retrieved on October 26, 2007, at http://www.whoi.edu/page.do?pid=12455&tid=282&cid=17906.

Schwartz, P. And Randall, D. (2004) an Abrupt Climate Change Scenario and Its Implications for United States National Security. Retrieved on October 26, 2007, at http://www.grist.org/pdf/AbruptClimateChange2003.pdf

WGBU (2006) the Future Oceans - Warming Up, Rising High, Turning Sour. Berlin: WGBU.

The Effects of Climate Change on Ocean Currents