Average of annual maximum thermal stress (DHW) values during 1985–2006. Significant coral bleaching was reported during periods with average thermal stress above 0.5°C-weeks, and was especially widespread in 1995, 1998, and 2005. Eakin, et al., 2010 

Average of annual maximum thermal stress, measured in Degree Heating Weeks (DHW), during 1985–2006. Significant coral bleaching was reported during periods with average thermal stress above 0.5°C-weeks, and was especially widespread in 1995, 1998, and 2005.

Thermal stress during the 2005 event exceeded any observed from the Caribbean in the prior 20 years, and regionally-averaged temperatures were the warmest in over 150 years. Comparison of satellite data against field surveys demonstrated a significant predictive relationship between accumulated heat stress (measured using NOAA Coral Reef Watch's Degree Heating Weeks) and bleaching intensity. This severe, widespread bleaching and mortality will undoubtedly have long-term consequences for reef ecosystems and suggests a troubled future for tropical marine ecosystems under a warming climate.

Eakin CM, Morgan JA, Heron SF, Smith TB, Liu G, et al. (2010) Caribbean Corals in Crisis: Record Thermal Stress, Bleaching, and Mortality in 2005. PLoS ONE 5(11): e13969. doi:10.1371/journal.pone.0013969

2 comments :

  1. RalphWiggum said...

    Is there any data, like with all the "little ice age" and concomitant warming periods, for the reef systems? Do they periodically die and come back? Or is this demonstrably a unique event in the historical record?

    (I am not being a GW skeptic. I'm just trying to anticipate their objections.)  

  2. Jim said...

    A fair question, and the simple answer is that while there's a lot of variability in coral growth, the simultaneous decline of coral colonies globally is something new, or at least rare.

    It can be shown that ocean chemistry is changing much faster than at any time in Earth's history; it's hard to argue that corals won't be affected adversely by this and all of the other stresses that humans are imposing (acidification, overfishing, etc.)

    Here's a recent paper that examines the question more closely: Climate records from corals.  

 

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