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Title: El Nino Influence on Holocene Reef Accretion in Hawai'i 
Author: Rooney, John; Fletcher, Charles; Grossman, Eric; Engles, Mary; Field, Michael
Date: 2004-04
Publisher: University of Hawai'i Press
Citation: Rooney J, Fletcher C, Grossman E, Engles M, Field M. 2004. El Nino influence on Holocene reef accretion in Hawai'i. Pac Sci 58(2): 305-324.
Abstract: New observations of reef accretion from several locations show that
in Hawai'i accretion during early to middle Holocene time occurred in areas
where today it is precluded by the wave regime, suggesting an increase in wave
energy. Accretion of coral and coralline algae reefs in the Hawaiian Islands today
is largely controlled by wave energy. Many coastal areas in the main Hawaiian
Islands are periodically exposed to large waves, in particular from North
Pacific swell and hurricanes. These are of sufficient intensity to prevent modern
net accretion as evidenced by the antecedent nature of the seafloor. Only in
areas sheltered from intense wave energy is active accretion observed. Analysis
of reef cores reveals patterns of rapid early Holocene accretion in several locations
that terminated by middle Holocene time, ca. 5000 yr ago. Previous analyses
have suggested that changes in Holocene accretion were a result of reef
growth "catching up" to sea level. New data and interpretations indicate that
the end of reef accretion in the middle Holocene may be influenced by factors in
addition to sea level. Reef accretion histories from the islands of Kaua'i, O'ahu,
and Moloka'i may be interpreted to suggest that a change in wave energy contributed
to the reduction or termination of Holocene accretion by 5000 yr ago
in some areas. In these cases, the decrease in reef accretion occurred before the
best estimates of the decrease in relative sea-level rise during the mid-Holocene
high stand of sea level in the main Hawaiian Islands. However, reef accretion
should decrease following the termination of relative sea-level rise (ca. 3000 yr
ago) if reef growth were "catching up" to sea level. Evidence indicates that rapid
accretion occurred at these sites in early Holocene time and that no permanent
accretion is occurring at these sites today. This pattern persists despite the
availability of hard substrate suitable for colonization at a wide range of depths
between -30 m and the intertidal zone. We infer that forcing other than relative
sea-level rise has altered the natural ability to support reef accretion on
Hawaiian insular shelves. The limiting factor in these areas today is wave
energy. Numbers of both large North Pacific swell events and hurricanes in
Hawai'i are greater during El Nino years. We infer that if these major reef-limiting
forces were suppressed, net accretion would occur in some areas in
Hawai'i that are now wave-limited. Studies have shown that El Nino/Southern
Oscillation (ENSO) was significantly weakened during early-mid Holocene
time, only attaining an intensity similar to the current one ca. 5000 yr ago. We
speculate that this shift in ENSO may assist in explaining patterns of Holocene
Hawaiian reef accretion that are different from those of the present and apparently
not related to relative sea-level rise.
ISSN: 0030-8870
URI: http://hdl.handle.net/10125/2727

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