Gourlay, M. R., and Colleter, G., 2005. Wave-generated flow on
coral reefs – an analysis for two dimensional horizontal reef-tops
with steep faces. Coastal Engineering, 52, 353–387.
Hardy, T. A., Young, I. R., Nelson, R. C., and Gourlay, M. R., 1990.
Wave attenuation on an offshore coral reef. In Proceedings of the
22nd Coastal Energy Conference, Delft, Vol. 1, pp. 330–344.
Hardy, T. A., and Young, I. R., 1996. Field study of wave attenuation on an offshore coral reef. Journal of Geophysical Research,
101, 14311–14326.
Massel, S. R., and Gourlay, M. R., 2000. On the modelling of wave
breaking and set-up on coral reefs. Coastal Engineering, 39, 1–27.
Rosenberg, E., and Loya, Y. (eds.), 2004. Coral Diseases. Springer,
p. 500.
Sheppard, C. R. C., Dixon, D. J., Gourlay, M., Sheppard, A. L. S.,
and Payet, R., 2005. Coral mortality increases wave energy
reaching shores protected by reef flats: examples from the Seychelles. Estuarine, Coastal and Shelf Science, 64, 223–234.
Cross-references
Climate Change: Impact of Sea Level Rise on Reef Flat Zonation
and Productivity
Climate Change: Increasing Storm Activity
Climate Change and Coral Reefs
Engineering On Coral Reefs With Emphasis On Pacific Reefs
Indian Ocean Reefs
Reef Flats
Reef Front Wave Energy
Sea Level Change and Its Effect on Reef Growth
CLIMATE CHANGE: INCREASING STORM ACTIVITY
Joshua Madin
Macquarie University, NSW, Sydney, Australia
Synonyms
Increasing ecological disturbance; Increasing tropical
cyclone (hurricane, typhoon) frequency and intensity
Definition
An increase in the intensity and/or frequency of storms relative to a predefined expectation (e.g., historic yearly
average or quantile).
Introduction
Increasing storm activity is a hypothesized consequence
of climate change that results predominantly from
warming sea surface temperatures (SST). Significant scientific debate revolves around whether or not the storm
activity is increasing and, if so, whether any increases
are a consequence of global warming. This debate exists
primarily because detecting such trends depends on the
temporal and spatial scales examined, the duration and
quality of available meteorological records, and the kinds
of statistical and mathematical approaches used in analyses. Storms temporarily alter the physical state of coral
reefs in a number of direct and indirect ways (see Tropical
Cyclone/Hurricane). Direct examples include changes in
salinity (via rainfall) and impinging wave climate
(via wind). Indirect examples include increased terrestrial
runoff and associated changes in turbidity, chemistry, and
human-induced pollution levels. By altering the physical
state of ecological communities, storms are an important
form of ecological disturbance that significantly shape
ecological systems and are hypothesized to be at least
partially responsible for the levels of species diversity.
Increasing storm activity will drive changes in the biological and physical structure of coral reefs, and in turn the
ecology of organisms that rely of on the reef habitat for
shelter. Although some studies have forged mechanistic
links between storm activity and coral reef vulnerability,
the impacts of increasing storm activity on coral reef ecology and physical structure of reefs remain largely
unknown (Figure 1).
Evidence
Theory suggests that tropical storm activity should
increase with global mean temperature as warmer seas
fuel tropical storm generation (Emanuel, 1991). While
growing evidence strongly suggests that SST is increasing in tropical seas (see Temperature Change: Bleaching),
evidence for increasing storm activity is less clear cut. Part
of the reason for this uncertainty is that storm activity is
comprised of two components that must be considered
simultaneously: storm intensity and storm frequency
(Figure 2). In general, more intense storms are less frequent (e.g., yearly cyclones) and less intense storms are
more frequent (e.g., daily to weekly squalls). An increase
in storm activity would theoretically shift this relationship
upward (illustrated by the arrow in Figure 2). Such a shift
can be interpreted in two ways. First, storms of a given
intensity would increase in frequency within a given time
period (A to A’, Figure 2; e.g., an increase in the number
of category 3 cyclones each year). Second, storms of
a given frequency would increase in intensity (B to B’,
Figure 2; e.g., the largest yearly storm is more intense on
average).
Early attempts to detect changes in storm activity
focused on frequency and uncovered no clear trends. In
fact, a more recent modeling effort suggests that Atlantic
tropical storm frequencies might even decrease under
future greenhouse-gas-induced warming (Knutson et al.,
2008). Despite possible decreases in storm frequencies,
studies (including Knutson et al., 2008) have shown that
storm intensity is increasing. For instance, Emanuel
(2005) looked at storm power dissipation (a measure of
the total energy generated by a storm) and found it to be
highly correlated with temperature, reflecting global
warming. These results appear paradoxical according to
Figure 2: how can tropical storm intensity increase but
yearly frequency decrease or stay unchanged? The answer
becomes apparent when looking at the distributions and
extremes of yearly storm intensities rather than averages
(Gaines and Denny, 1993). In a study looking at the maximum wind speeds generated by tropical cyclones, Elsner
218
CLIMATE CHANGE: INCREASING STORM ACTIVITY
coral reefs – an analysis for two dimensional horizontal reef-tops
with steep faces. Coastal Engineering, 52, 353–387.
Hardy, T. A., Young, I. R., Nelson, R. C., and Gourlay, M. R., 1990.
Wave attenuation on an offshore coral reef. In Proceedings of the
22nd Coastal Energy Conference, Delft, Vol. 1, pp. 330–344.
Hardy, T. A., and Young, I. R., 1996. Field study of wave attenuation on an offshore coral reef. Journal of Geophysical Research,
101, 14311–14326.
Massel, S. R., and Gourlay, M. R., 2000. On the modelling of wave
breaking and set-up on coral reefs. Coastal Engineering, 39, 1–27.
Rosenberg, E., and Loya, Y. (eds.), 2004. Coral Diseases. Springer,
p. 500.
Sheppard, C. R. C., Dixon, D. J., Gourlay, M., Sheppard, A. L. S.,
and Payet, R., 2005. Coral mortality increases wave energy
reaching shores protected by reef flats: examples from the Seychelles. Estuarine, Coastal and Shelf Science, 64, 223–234.
Cross-references
Climate Change: Impact of Sea Level Rise on Reef Flat Zonation
and Productivity
Climate Change: Increasing Storm Activity
Climate Change and Coral Reefs
Engineering On Coral Reefs With Emphasis On Pacific Reefs
Indian Ocean Reefs
Reef Flats
Reef Front Wave Energy
Sea Level Change and Its Effect on Reef Growth
CLIMATE CHANGE: INCREASING STORM ACTIVITY
Joshua Madin
Macquarie University, NSW, Sydney, Australia
Synonyms
Increasing ecological disturbance; Increasing tropical
cyclone (hurricane, typhoon) frequency and intensity
Definition
An increase in the intensity and/or frequency of storms relative to a predefined expectation (e.g., historic yearly
average or quantile).
Introduction
Increasing storm activity is a hypothesized consequence
of climate change that results predominantly from
warming sea surface temperatures (SST). Significant scientific debate revolves around whether or not the storm
activity is increasing and, if so, whether any increases
are a consequence of global warming. This debate exists
primarily because detecting such trends depends on the
temporal and spatial scales examined, the duration and
quality of available meteorological records, and the kinds
of statistical and mathematical approaches used in analyses. Storms temporarily alter the physical state of coral
reefs in a number of direct and indirect ways (see Tropical
Cyclone/Hurricane). Direct examples include changes in
salinity (via rainfall) and impinging wave climate
(via wind). Indirect examples include increased terrestrial
runoff and associated changes in turbidity, chemistry, and
human-induced pollution levels. By altering the physical
state of ecological communities, storms are an important
form of ecological disturbance that significantly shape
ecological systems and are hypothesized to be at least
partially responsible for the levels of species diversity.
Increasing storm activity will drive changes in the biological and physical structure of coral reefs, and in turn the
ecology of organisms that rely of on the reef habitat for
shelter. Although some studies have forged mechanistic
links between storm activity and coral reef vulnerability,
the impacts of increasing storm activity on coral reef ecology and physical structure of reefs remain largely
unknown (Figure 1).
Evidence
Theory suggests that tropical storm activity should
increase with global mean temperature as warmer seas
fuel tropical storm generation (Emanuel, 1991). While
growing evidence strongly suggests that SST is increasing in tropical seas (see Temperature Change: Bleaching),
evidence for increasing storm activity is less clear cut. Part
of the reason for this uncertainty is that storm activity is
comprised of two components that must be considered
simultaneously: storm intensity and storm frequency
(Figure 2). In general, more intense storms are less frequent (e.g., yearly cyclones) and less intense storms are
more frequent (e.g., daily to weekly squalls). An increase
in storm activity would theoretically shift this relationship
upward (illustrated by the arrow in Figure 2). Such a shift
can be interpreted in two ways. First, storms of a given
intensity would increase in frequency within a given time
period (A to A’, Figure 2; e.g., an increase in the number
of category 3 cyclones each year). Second, storms of
a given frequency would increase in intensity (B to B’,
Figure 2; e.g., the largest yearly storm is more intense on
average).
Early attempts to detect changes in storm activity
focused on frequency and uncovered no clear trends. In
fact, a more recent modeling effort suggests that Atlantic
tropical storm frequencies might even decrease under
future greenhouse-gas-induced warming (Knutson et al.,
2008). Despite possible decreases in storm frequencies,
studies (including Knutson et al., 2008) have shown that
storm intensity is increasing. For instance, Emanuel
(2005) looked at storm power dissipation (a measure of
the total energy generated by a storm) and found it to be
highly correlated with temperature, reflecting global
warming. These results appear paradoxical according to
Figure 2: how can tropical storm intensity increase but
yearly frequency decrease or stay unchanged? The answer
becomes apparent when looking at the distributions and
extremes of yearly storm intensities rather than averages
(Gaines and Denny, 1993). In a study looking at the maximum wind speeds generated by tropical cyclones, Elsner
218
CLIMATE CHANGE: INCREASING STORM ACTIVITY