Flooding of a Pacific Atoll Island: Diagnosing the Problem
John Hunter
Antarctic Climate & Ecosystems
Cooperative Research Centre
Hobart, Tasmania, Australia Introduction
I visited Takuu Atoll for 26 days during Nov. and Dec. 2008, supported by documentaries film−makers from New Zealand Introduction
I visited Takuu Atoll for 26 days during Nov. and Dec. 2008, supported by documentaries film−makers from New Zealand
Object was to provide scientific background for film about effect of climate change on a Pacific island Introduction
I visited Takuu Atoll for 26 days during Nov. and Dec. 2008, supported by documentaries film−makers from New Zealand
Object was to provide scientific background for film about effect of climate change on a Pacific island
The other scientist was Scott Smithers, James Cook University Introduction
I visited Takuu Atoll for 26 days during Nov. and Dec. 2008, supported by documentaries film−makers from New Zealand
Object was to provide scientific background for film about effect of climate change on a Pacific island
The other scientist was Scott Smithers, James Cook University
Acknowledgements: Briar March and Lyn Collie, On the Level Productions Tim Bayliss−Smith, University of Cambridge Aquenal Pty Ltd and John Gibson for the loan of pressure recorders Two Perceptions .....
The Independent (UK), speaking about Takuu Atoll:
The 400 inhabitants of the atoll off the coast of Papua New Guinea are likely to be the first people in the world to lose their homeland to global warming. . . . Now the islanders . . . have been told that they have at best five years, and at worst a few months, before their homes vanish for ever beneath the waves. Two Perceptions .....
The Independent (UK), speaking about Takuu Atoll:
The 400 inhabitants of the atoll off the coast of Papua New Guinea are likely to be the first people in the world to lose their homeland to global warming. . . . Now the islanders . . . have been told that they have at best five years, and at worst a few months, before their homes vanish for ever beneath the waves. 26 November 2000 Two Perceptions .....
The Independent (UK), speaking about Takuu Atoll:
The 400 inhabitants of the atoll off the coast of Papua New Guinea are likely to be the first people in the world to lose their homeland to global warming. . . . Now the islanders . . . have been told that they have at best five years, and at worst a few months, before their homes vanish for ever beneath the waves. 26 November 2000
Ian Mott (Australian ‘climate sceptic’):
Most coral atolls are on volcanic peaks and these are usually made up of comparatively spongy rock . . . . And the weight of the coral and the soaking of water actually makes them all prone to sinking . . . this was first recognised by none other than Charles Darwin a century ago. Takuu Atoll (the Mortlock Islands)
CARTERETS
TAKUU ATOLL (MORTLOCKS)
BOUGAINVILLE Takuu Atoll (the Mortlock Islands)
CARTERETS
TAKUU ATOLL (MORTLOCKS)
BOUGAINVILLE
NUKUTOA Takuu Atoll (the Mortlock Islands)
CARTERETS NUKUTOA
TAKUU ATOLL (MORTLOCKS)
BOUGAINVILLE
NUKUTOA Our Observations
Collection of anectodal information Anecdotal Information on Flooding
From one−to−one interviews and a public meeting Anecdotal Information on Flooding
From one−to−one interviews and a public meeting
Significant flooding of Nukutoa at following times: 1940s 1950s 1962/1963 About 1973 1980s December 2008 (when we were there) Anecdotal Information on Flooding
From one−to−one interviews and a public meeting
Significant flooding of Nukutoa at following times: 1940s 1950s 1962/1963 About 1973 1980s December 2008 (when we were there)
So roughly every 10 years but gap of around 20 years from 1980s to 2008 Anecdotal Information on Flooding
From one−to−one interviews and a public meeting
Significant flooding of Nukutoa at following times: 1940s 1950s 1962/1963 About 1973 1980s December 2008 (when we were there)
So roughly every 10 years but gap of around 20 years from 1980s to 2008
No evidence for increase of flooding frequency during last 60 years Our Observations
Collection of anectodal information
Air photos and satellite images Nukutoa in 1943 and Now
100 metres
1943
Source of 1943 coastline: Tim Bayliss−Smith Our Observations
Collection of anectodal information
Air photos and satellite images
Tide−gauge observations (pressure gauges and barometers) Tide−Gauge Observations on Nukutoa
HAT -1 MHHW
-1.5
MSL
-2 Height (m above NC01)
MLLW -2.5 observations LAT predictions
325 330 335 340 345 Days from 00:00 1/1/2008 (time zone +10:00) Tide−Gauge Observations on Nukutoa
HAT -1 Positive surge MHHW
-1.5
MSL
-2 Height (m above NC01)
MLLW -2.5 observations LAT predictions
325 330 335 340 345 Days from 00:00 1/1/2008 (time zone +10:00) Tide−Gauge Observations on Nukutoa
HAT -1 Positive surge MHHW
-1.5
MSL
-2 Height (m above NC01)
MLLW -2.5 observations LAT predictions
325 330 335 340 345 Days from 00:00 1/1/2008 (time zone +10:00) Our Observations
Collection of anectodal information
Air photos and satellite images
Tide−gauge observations (pressure gauges and barometers)
Levelling of fossil and live coral microatolls Tide−Gauge Observations on Nukutoa
HAT -1 MHHW
-1.5
MSL
-2 Av. LW Height (m above NC01)
MLLW -2.5 observations LAT predictions
325 330 335 340 345 Days from 00:00 1/1/2008 (time zone +10:00) Tide−Gauge Observations on Nukutoa
HAT -1 MHHW
-1.5
MSL Range of tops of fossil microatolls -2 Av. LW Height (m above NC01)
MLLW -2.5 observations LAT predictions
325 330 335 340 345 Days from 00:00 1/1/2008 (time zone +10:00) Tide−Gauge Observations on Nukutoa
0.47 m − constrains vertical motion to ~0.1 mm/yr HAT -1 MHHW
-1.5
MSL Range of tops of fossil microatolls -2 Av. LW Height (m above NC01)
MLLW -2.5 observations LAT predictions
325 330 335 340 345 Days from 00:00 1/1/2008 (time zone +10:00) Our Observations
Collection of anectodal information
Air photos and satellite images
Tide−gauge observations (pressure gauges and barometers)
Levelling of fossil and live coral microatolls
Sampling of fossil and live coral microatolls Our Observations
Collection of anectodal information
Air photos and satellite images
Tide−gauge observations (pressure gauges and barometers)
Levelling of fossil and live coral microatolls
Sampling of fossil and live coral microatolls Our Observations
Collection of anectodal information
Air photos and satellite images
Tide−gauge observations (pressure gauges and barometers)
Levelling of fossil and live coral microatolls
Sampling of fossil and live coral microatolls
Installation of survey marks and land levelling surveys West−East Transect Through Nukutoa
0.2
0.0
−0.2
−0.4
−0.6 Vertical distance (m) −0.8
−1.0
0 100 200 300 400 Horizontal distance (m) West−East Transect Through Nukutoa
0.2
0.0
−0.2
−0.4
−0.6 Vertical distance (m) −0.8 HAT
−1.0
0 100 200 300 400 Horizontal distance (m) West−East Transect Through Nukutoa
0.2
0.0
−0.2
−0.4
−0.6 Vertical distance (m) Highest level on tide gauge, 10/12/2008 −0.8 HAT
−1.0
0 100 200 300 400 Horizontal distance (m) West−East Transect Through Nukutoa
0.2
0.0
−0.2
−0.4 Estimated max. inundation, 10/12/2008
−0.6 Vertical distance (m) Highest level on tide gauge, 10/12/2008 −0.8 HAT
−1.0
0 100 200 300 400 Horizontal distance (m) Our Observations
Collection of anectodal information
Air photos and satellite images
Tide−gauge observations (pressure gauges and barometers)
Levelling of fossil and live coral microatolls
Sampling of fossil and live coral microatolls
Installation of survey marks and land levelling surveys
Various observations during and after flooding of 10/12/2008 The Flooding of 10 December 2008
Caused by a combination of:
High tide close to HAT
A barometric surge (5−10 cm)
Long−period waves − hydraulic jumps of period 5−10 minutes (varying wave setup caused by breaking waves on fringing reef?) A Hydraulic Jump A Hydraulic Jump The Flooding of 10 December 2008
Caused by a combination of:
High tide close to HAT
A barometric surge (5−10 cm)
Long−period waves − hydraulic jumps of period 5−10 minutes (varying wave setup caused by breaking waves on fringing reef?)
Inundated more than half of Nukutoa Normal Coastline of Nukutoa Coastline of Nukutoa, 10 Dec. 2008 The Flooding of 10 December 2008
Caused by a combination of:
High tide close to HAT
A barometric surge (5−10 cm)
Long−period waves − hydraulic jumps of period 5−10 minutes (varying wave setup caused by breaking waves on fringing reef?)
Inundated more than half of Nukutoa
Damaged around 20 huts Flooding Damage The Flooding of 10 December 2008
Caused by a combination of:
High tide close to HAT
A barometric surge (5−10 cm)
Long−period waves − hydraulic jumps of period 5−10 minutes (varying wave setup caused by breaking waves on fringing reef?)
Inundated more than half of Nukutoa
Damaged around 20 huts
Destroyed school library The School Library Damaged Schoolbooks What We Learned No clear evidence for increase in flooding frequency What We Learned No clear evidence for increase in flooding frequency
Recent flooding is mainly of land more recently developed and reclaimed What We Learned No clear evidence for increase in flooding frequency
Recent flooding is mainly of land more recently developed and reclaimed
Seawalls not generally a good thing:
Remove beaches Reclaimed land is vulnerable to flooding During a flooding event, debris from seawalls are dangerous projectiles What We Learned No clear evidence for increase in flooding frequency
Recent flooding is mainly of land more recently developed and reclaimed
Seawalls not generally a good thing:
Remove beaches Reclaimed land is vulnerable to flooding During a flooding event, debris from seawalls are dangerous projectiles
No evidence for physical sinking of atoll (probably < 0.1 mm/year) What We Learned No clear evidence for increase in flooding frequency
Recent flooding is mainly of land more recently developed and reclaimed
Seawalls not generally a good thing:
Remove beaches Reclaimed land is vulnerable to flooding During a flooding event, debris from seawalls are dangerous projectiles
No evidence for physical sinking of atoll (probably < 0.1 mm/year)
Nukutoa is very vulnerable to flooding, even without sea−level rise What We Learned No clear evidence for increase in flooding frequency
Recent flooding is mainly of land more recently developed and reclaimed
Seawalls not generally a good thing:
Remove beaches Reclaimed land is vulnerable to flooding During a flooding event, debris from seawalls are dangerous projectiles
No evidence for physical sinking of atoll (probably < 0.1 mm/year)
Nukutoa is very vulnerable to flooding, even without sea−level rise
Nukutoa could probably survive sea−level rise for this century at least What We Learned No clear evidence for increase in flooding frequency
Recent flooding is mainly of land more recently developed and reclaimed
Seawalls not generally a good thing:
Remove beaches Reclaimed land is vulnerable to flooding During a flooding event, debris from seawalls are dangerous projectiles
No evidence for physical sinking of atoll (probably < 0.1 mm/year)
Nukutoa is very vulnerable to flooding, even without sea−level rise
Nukutoa could probably survive sea−level rise for this century at least
..... so long as coral can survive global warming and ocean acidification
Tide−Gauge Observations on Nukutoa
HAT -1 MHHW
-1.5
MSL
-2 Av. LW Height (m above NC01)
MLLW -2.5 observations LAT predictions Top of live microatoll
325 330 335 340 345 Days from 00:00 1/1/2008 (time zone +10:00) Tide−Gauge Observations on Nukutoa
0.54 m − limited by low sea level during El Nino? HAT -1 MHHW
-1.5
MSL
-2 Av. LW Height (m above NC01)
MLLW -2.5 observations LAT predictions Top of live microatoll
325 330 335 340 345 Days from 00:00 1/1/2008 (time zone +10:00) Tide−Gauge Observations at Honiara (609 km From Nukutoa)
1
0.9
0.8
0.7
0.6
Sea level (m) 0.5
0.4
0.3
0.2 1970 1975 1980 1985 1990 1995 2000 2005 2010 Year