Coral starving, survival & MWP

Mark Eakin Mark.Eakin at
Mon Mar 25 11:56:29 EST 2002


You have raised some good points regarding the Medieval Warm Period (MWP).
As Mike pointed out in his response, the largest problem there is a lack of
data.  Esper et al. paper from last week's Science indicates that MWP
temperatures may have been higher than estimated in earlier temperature
reconstructions like Mann et al. 1999.  However, the Esper et al.
reconstruction does not show a dramatic and singular rise going into the
MWP, unlike the nearly linear increase it shows for 1800-date.

We need to keep in mind that these are temperate, Northern  Hemisphere,
terrestrial reconstructions.  Even the Mann et al. reconstruction used a
very small amount of marine data (mostly 1500-date) and reconstructed ocean
surface data from functions primarily based on temperate, terrestrial data.
You can compare a wide array of reconstruction data by looking at

All of this points to the need for data on reef temperatures during the
MWP.  The climate system does not change in ways that are spatially
consistent with temperate, Northern Hemisphere indices.  Without real
information on reef temperatures, I think comparisons with the MWP are a bit
premature, but useful thoughts for building hypotheses.


Debbie MacKenzie wrote:

> Hi Pedro,
> you wrote:
> >I decided to add a little more firewood to discussion on Debbie
> >McKenzie's interesting coral starving-survival hypohesis.
> >...//...
> >Probably well fed Acropora palmata crests survived the massive
> >mortality event(s) (cause unknown: coral bleaching, white band,
> >patchy necrosis?) that killed the crests exposed to less nutrified
> >and less productive oceanic waters.
> >If so, McKenzie's hypothesis, far from be discarded prematurely,
> >has to be tested because it could explain differences in the fate of
> >some coral reefs at small scale, and also explain some
> >mismatches at larger scale when correlating coral bleaching with
> >sea surface temperature.
> Thanks very much Pedro!
> It is well beyond my means to do anything about testing the hypothesis,
> but
> I really hope that someone will investigate it.
> Regarding the role of high temperatures in causing mass bleaching and
> death
> of corals, what do you make of the "Medieval Warm Period?" From what I've
> read, have not Acroporas a history of dominating Caribbean reefs for many
> thousands of years before the onset of their recent decline due to
> diseases
> and bleaching? If the "mass bleaching" cause of death were strictly the
> result of the recent temperature increase, should not the records from the
> "Medieval warm period" (about 1000 years ago) also show a period of
> decline
> in Acropora? Apparently today's higher temperatures are similar to what
> occurred at that time (although the existence of the Medieval warm period
> has been debated in some circles, there seems to be lots of evidence for
> it, from diverse areas of the globe). If temperatures as high as today's
> occurred a thousand years ago without causing mass mortality in corals,
> the
> corals must have had a greater resistance to heat stress in those days...a
> greater resilience attributable to what? Well, one main difference in
> their
> environment that comes to mind is the fact that the bulk of other forms of
> marine life involved in nutrient cycling was far greater 1000 years ago
> than it is today. (Here's a news clip that I noticed today about the
> Medieval warm period:
> )
> cheers,
> Debbie MacKenzie
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C. Mark Eakin, Ph.D.
Chief of NOAA Paleoclimatology Program and
Director of the World Data Center for Paleoclimatology

NOAA/National Geophysical Data Center
325 Broadway E/GC
Boulder, CO 80305-3328
Voice: 303-497-6172                  Fax: 303-497-6513
Internet: mark.eakin at

  C. Mark Eakin <mark.eakin at>
  Chief and Director of World Data Center for Paleoclimatology
  Paleoclimatology Program

  C. Mark Eakin
  Chief and Director of World Data Center for  <mark.eakin at>
  Paleoclimatology Program
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