[Coral-List] Great Barrier Reef heat stress history

[Thomas De Carlo]

Dear Coral-List,

I would like to draw your attention to our new paper in PeerJ on the
history of heat stress and coral bleaching on the Great Barrier Reef:
https://peerj.com/articles/7473/

There are a few key points:

1) We used long-term temperature logger data to evaluate the precision and
accuracy and various satellite SST products for capturing heat stress along
the GBR. We found that OI-SSTv2 is the best choice for inter-annual
analyses because it is the most accurate product prior to the past few
years, and critically, it does not have large changes in bias over time.
The recent 5-km version of Coral Reef Watch is great for a high-precision
snapshot during the past few years, but appears to have substantial biases
in the early 2000s. Thus, SST products should be chosen carefully based on
the question(s) to be addressed.

2) We really need to consider times when there was intense heat stress but
not bleaching. On the GBR, all the major bleaching events occurred during
bleaching-level heat stress (i.e. using the degree heating weeks
thresholds), but not all bleaching-level heat stress events caused
bleaching. In particular, 2004 stands out as a year of very high
temperatures, but very low levels of bleaching.

3) Ocean currents appear to play an important role in bleaching. For
example, bleaching events on the GBR have occurred under the combination of
heat stress and an unusually strong offshore current (the East Australian
Current, or "EAC"), which drives upwelling along the central and southern
GBR. Conversely, during 2004, temperatures were exceptionally high but the
EAC was exceptionally slow (reduced upwelling), and the corals did not
bleach. This is consistent with some of the recent work highlighting the
important role of nutrients in modulating coral bleaching.

Sincerely,
Tom DeCarlo

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