11.3.3 Changes in Extreme Sea Levels: Storm Surges and Waves
Lack of adequate data sets means we can not ascertain whether there have been
changes in the magnitude and/or frequency of storm surges (aperiodic changes
associated with major meteorological disturbances resulting in sea level changes
of up to several metres and lasting a few hours to days) in many regions of
the world. Zhang et al. (1997, 2000) performed a comprehensive analysis of hourly
tide gauge data from the east coast of North America, and concluded that there
had been no discernible secular trend in storm activity or severity during the
past century. European analyses include that of Woodworth (1999b), who found
no significant increase in extreme high water level distributions from Liverpool
from 1768 to 1993 to those from later epochs, other than what can be explained
in terms of changes in local tidal amplitudes, mean sea level and vertical land
movement. Vassie (reported in Pugh and Maul, 1999) and Bijl et al. (1999) concluded
that there was no discernible trend over the last century in the statistics
of non-tidal sea level variability around the UK and the eastern North Sea (Denmark,
Germany and the Netherlands), above the considerable natural sea level variability
on decadal time-scales. In South America, DOnofrio et al. (1999) observed
a trend of extreme levels at Buenos Aires of 2.8 mm/yr over 1905 to 1993. On
the basis of available statistics, the South American result is consistent with
the local mean sea level trend.
| Table 11.11: Sea level rise
from thermal expansion from AOGCM experiments following the IS92a scenario
for the 21st century, including the direct effect of sulphate aerosols.
See Chapter 8, Table 8.1
and Chapter 9, Table 9.1
for further details of models and experiments. See Table
11.2 for thermal expansion from AOGCM experiments for the 20th century. |
 |
| Experiment |
 .Tg
(°C) |
Sea level rise (m) |
| |
1990 to 2090a
|
1990 to 2040
|
1990 to 2090a
|
| CGCM1 GS |
3.7
|
0.12
|
0.37
|
| CGCM2 GS |
3.6
|
0.11
|
0.33
|
| CSIRO Mk2 GS |
2.7
|
0.11
|
0.28
|
| ECHAM4/OPYC3 GSb |
—
|
0.11
|
—
|
| GFDL_R15_a GSc |
—
|
0.13
|
—
|
| GFDL_R15_b GS |
3.2
|
0.12
|
0.29
|
| GFDL_R30_c GS |
2.8
|
0.12
|
0.31
|
| HadCM2 GS |
2.5
|
0.07
|
0.20
|
| HadCM3 GSIO |
2.8
|
0.07
|
0.20
|
| MRI2 GS |
1.5
|
0.04
|
0.09
|
| DOE PCM GS |
1.9
|
0.07
|
0.17
|
|
Variations in surge statistics can also be inferred from analysis of meteorological
data. Kass et al. (1996) and the WASA Group (1998) showed that there are no
significant overall trends in windiness and cyclonic activity over the North
Atlantic and north-west Europe during the past century, although major variations
on decadal times-scales exist. An increase in storminess in the north-east Atlantic
in the last few decades (Schmith et al., 1998) and a recent trend towards higher
storm surge levels on the German and Danish coasts (Langenberg et al., 1999)
is consistent with natural variability evident over the last 150 years. Pirazzoli
(2000) detected evidence for a slight decrease in the main factors contributing
to surge development on the French Atlantic coast in the last 50 years. Correlation
between the frequency of Atlantic storms and ENSO was demonstrated by Van der
Vink et al. (1998).
| Table 11.12: Calculations of
glacier melt from AOGCM experiments following the IS92a scenario for the
21st century, including the direct effect of sulphate aerosols. See Tables
8.1 and 9.1 for further details of models
and experiments. |
|
| Experiment |
B (mm/yr)
1990
|
T g
(°C)
1990 to 2090 |
Sea level rise (m)
1990 to 2090
|
ðB/ðTg
(mm/yr/°C)
|
| |
|
|
Constant
area
|
Changing
area
|
|
| CGCM1 GS |
0.43
|
3.7
|
0.15
|
0.11
|
0.65
|
| CSIRO Mk2 GS |
0.52
|
2.7
|
0.15
|
0.11
|
0.73
|
| CSM 1.3 GS |
0.45
|
1.8
|
0.10
|
0.07
|
0.61
|
| ECHAM4/OPYC3 GSa |
0.56
|
|
|
|
0.64
|
| GFDL_R15_a GSb |
0.42
|
|
|
|
0.58
|
| GFDL_R15_b GS |
0.44
|
3.2
|
0.13
|
0.09
|
0.54
|
| GFDL_R30_c GS |
0.33
|
2.8
|
0.12
|
0.08
|
0.53
|
| HadCM2 GSc |
0.44
|
2.5
|
0.11
|
0.08
|
0.61
|
| HadCM3 GSIO |
0.31
|
2.8
|
0.11
|
0.08
|
0.62
|
| MRI2 GS |
0.22
|
1.5
|
0.06
|
0.05
|
0.60
|
| DOE PCM GS |
0.42
|
1.9
|
0.09
|
0.06
|
0.59
|
|
Increases in wave heights of approximately 2 to 3 m over the period 1962 to
1985 off Lands End, south-west England (Carter and Draper, 1988), increases
in wave height over a neighbouring area at about 2%/yr since 1950 (Bacon and
Carter, 1991, 1993) and wave height variations simulated by the Wave Action
Model (WAM) (Günther et al., 1998) are all consistent with decadal variations
over most of the north-east Atlantic and North Sea. This variability could be
related to the NAO (Chapter 2, Section
2.6.5).
| Table 11.13: Calculations of ice
sheet mass changes using temperature and precipitation changes from AOGCM
experiments following the IS92a scenario for the 21st century, including
the direct effect of sulphate aerosols, to derive boundary conditions for
an ice sheet model. See Tables 8.1 and 9.1
for further details of models and experiments. |
|
| Experiment |
Greenland |
Antarctica |
| |
Sea level rise (m)
1990 to 2090
|
Sensitivity
(mm/yr/ °C)
|
T/ Tg |
1/P
dP/dT
(%/°C)
|
Sea level rise (m)
1990 to 2090
|
Sensitivity
(mm/yr/ °C)
|
T/
T g |
| |
dB/dTg
|
dB/dT
|
dB/dTg
|
dB/dT
|
| CGCM1 GS |
0.03
|
0.13
|
0.10
|
1.3
|
2.7
|
0.02
|
0.12
|
0.11
|
1.1
|
| CSIRO Mk2 GS |
0.02
|
0.16
|
0.08
|
2.0
|
5.9
|
0.07
|
0.37
|
0.33
|
1.1
|
| CSM 1.3 GS |
0.02
|
0.15
|
0.05
|
3.1
|
7.8
|
0.04
|
0.31
|
0.27
|
1.1
|
| ECHAM4/OPYC3 GS a |
|
0.03
|
0.03
|
1.2
|
6.5
|
|
0.48
|
0.32
|
1.5
|
| GFDL_R15_a GS b |
|
0.12
|
0.06
|
1.9
|
4.1
|
|
0.18
|
0.22
|
0.8
|
| HadCM2 GS |
0.02
|
0.10
|
0.07
|
1.4
|
4.0
|
0.04
|
0.21
|
0.17
|
1.2
|
| HadCM3 GSIO |
0.02
|
0.09
|
0.06
|
1.4
|
4.5
|
0.07
|
0.35
|
0.28
|
1.3
|
| MRI2 GS |
0.01
|
0.08
|
0.05
|
1.6
|
4.4
|
0.01
|
0.14
|
0.12
|
1.2
|
| DOE PCM GS |
0.02
|
0.14
|
0.06
|
2.2
|
5.6
|
0.07
|
0.48
|
0.30
|
1.6
|
|
