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References Golding B, Clark P, May B. 2005. The Sibley AM. 2009. Analysis of the North Boscastle Flood: Meteorological York Moors storms – 19 June 2005. BBC News. 2007. Storms lead to major analysis of the conditions leading to Weather 64: 39–42. disruption, 21August 2007. flooding on 16 2004. Weather 60:

http://news.bbc.co.uk/1/hi/england/ 230–235. Coastal thunderstorms in Kent kent/6956195.stm [Accessed January 2009]. Kent News. 2007. Whitstable ‘no-go’ zone Canterbury City Council. 2008. Report Correspondence to: Andrew Sibley, as floods hit, 21 August 2007 Met Office, FitzRoy Road, on flooding incident at Whitstable on 21 http://www.kentnews.co.uk/kent-news/ August 2007, Joint Transportation Board Whitstable-_no__go_-zone-as-floods-hit- Exeter, EX1 3PB, UK. of Canterbury City Council, Item 10, 18 newsinkent4700.aspx [Accessed February Email: [email protected] March 2008. http://www2.canterbury. 2009]. gov.uk/committee/Data/Joint%20Trans © Crown Copyright, 2009, published with the Mayes J, Winterton J. 2008. The West portation%20Board/20080318/Agenda/ Surrey Thunderstorm, 13 August 2006. permission of the Controller of HMSO and the $Agenda%20Enclosure%208.doc.pdf Weather 63: 50–55. Queen’s Printer for [Accessed January 2009]. DOI: 10.1002/wea.453 Weather – August 2009, Vol. 64, No. 8 A study of sea-level changes in the for the last 16 years

Than Aung, Awnesh Singh A brief background history of at olls or that rise but a few the study area metres above sea level. In most places it is and Uma Prasad less than a metre above sea level. University of the South Pacific, Kiribati, officially known as the Republic of Kiribati, is an nation located in the central tropical . It comprises The Australian Project – South Introduction 32 and one island – (Figure 1). Pacific Sea Level and The inhabitants of every Pacific island The total land area, however, is only approxi- and island are convinced that the changes mately 726km2. According to a population Monitoring Project they are observing in their islands today are, estimate in 2005, it has slightly over In response to concerns raised by the Pacific in many cases, very different from what they 100 000 inhabitants – a population density island countries over the potential impacts of observed one or more decades ago. These of 137 people per km2. The name Kiribati is an enhanced greenhouse effect on climate include extensive coastal , persist- pronounced as kiribas and is the Kiribati ren- and sea levels in the South Pacific , ent alteration of regional weather patterns dering of ‘Gilberts’ derived from the English the South Pacific Sea Level and Climate and decreased productivity in fisheries and name for the main group of islands: the Monitoring Project was set up in the early agriculture. Higher sea levels are making former . The island groups 1990s. It has been fully funded by AusAID for some too saline for cultivation of crops include Gilbert Islands, and the forum region, which includes , such as , pulaka and yams. Coastal roads, (www.wikipedia.org, 2007). , , , Federated States bridges, foreshores and plantations are suf- Banaba is an isolated island between of , Fiji, , , fering increased erosion, even on islands Nauru and the Gilbert Islands. It is a raised Kiribati, , , that have not experienced inappropriate that was once a rich source of , , , and Cook coastal development. Recent devastating phos phates. The rest of the land in Kiribati Islands. As part of the project, a SEAFRAME droughts have hit export crops and caused consists of sand and rock and of (SEA level Fine Resolution Acoustic serious water shortages in many Pacific island countries, including the Federated States of Micronesia, Fiji, Marshall Islands, , Samoa, Tuvalu, Kiribati and Tonga (Flannery, 2005). At this point, it is worth referring to the words of the 2006 Australian of the Year. In Chapter 32 – The Last Act of God – of The Weather Makers, Prof. Tim Flannery com- mented that the inhabitants of lands imme- diately vulnerable to are five atoll countries: Kiribati, , Marshall Islands, and Tuvalu (Flannery, 2005). As a result of the destruction of the ’s coral reefs, rising sea levels and the inten- sifying weather events already in train, it seems inevitable that these nations will be destroyed by climate change during the course of this century. Figure 1. Map of Kiribati. (Source: http://www.spto.org/spto/export/pics/spto/kiribati_map.gif) 203 Measuring Equipment) gauge was installed magnitude of erosion or the likely mode estimates of the magnitude of change that in , Kiribati, in December 1992. The of physical response of low-lying islands to would occur under different sea-level-rise gauge has been returning high resolution, sea-level rise. scenarios for specific sites, such as South good scientific quality data, since then. By definition, coastal erosion is the natural Tarawa in Kiribati. All simulations show that SEAFRAME gauges not only measure sea process that has been occurring throughout sea-level rise promotes physical changes in level by two independent means, but also the history of most small islands and causes shorelines, but the shoreline change does a number of ancillary variables, such as air a long-term loss of land. The more impor- not always result in erosion or net loss of and water temperatures, wind speed, wind tant point is to establish if the erosion is land. This of information is important direction, wind gust and atmospheric pres- exacerbated by rising sea levels or not. It is for management purposes when examining sure. There is an associated programme of to be noted that erosion has increased dras- atoll island vulnerability. levelling to determine vertical movement tically in many islands as a result of inappro- of the sea-level sensors due to local land priate human interaction and management. Sea level in the Kiribati Area in the Kiribati Sea level Sea-level trends in the Kiribati movement. Continuous Global Positioning The building of causeways (e.g. to link the System (CGPS) measurements are also islands), the insertion of groins and seawalls, region for the last 16 years now being made to determine the vertical and sand extraction and harbour develop- Most Pacific islanders are fully aware that movement of the land with respect to the ments are all activities that have promoted the sea level is controlled by many factors; International Terrestrial Frame. erosion. In Kiribati, for example, there has these include the periodic tides, the more When considering the data length for been extensive monitoring conducted for occasional violent outcome of cyclones and trend calculations with reasonable certainty, with a particular focus on the prolonged effects of El Niño. All of these it was appropriate to introduce a term Node the effects that the Nippon has changes have a direct effect on their lives. Cycle – defined as a period of approximately had on nearby coastal erosion. According The effects vary widely across the region. 18.61 Julian years required for the regression to Harvey and Mitchell (2003), much of the Along the Melanesian , from of the Moon’s nodes to complete a circuit of coastal change caused by human impact is Manus Island (PNG) to Vanuatu, tides are 360° of longitude. It is accompanied by a likely to exceed any impact which could be predominantly diurnal, or once daily, while Weather – August 2009, Vol. 64, No. 8 64, No. Vol. – August 2009, Weather corresponding cycle of changing inclination attributable to natural sea-level change. elsewhere the tides are semidiurnal, that is, of the Moon’s orbit relative to the plane of Referring to the information from the each day tends to have two highs and two the , with resulting inequalities in South Pacific Regional Environmental lows. Tropical cyclones, which are fuelled the rise and fall of the tide and speed of the Program, however, two small uninhabited by heat stored in the upper ocean, tend tidal currents (Rockville, 1989). Kiribati islets – Tebua Tarawa and Abanuea to occur in the hottest months. They tend According to Rockville (1989), the specific – disappeared underwater in 1999. Tebua’s not to occur within 5° of the Equator due 19-year period is adopted as the official time disappearance is a real sign that global to the weakness of the Coriolis force – a segment over which tide observations are warming is making itself felt in the Pacific. rather subtle effect of the Earth’s rotation. taken and reduced to obtain mean values While some erosion can be blamed on inap- Figure 2 depicts the evolution of the short- for tidal datum. It is necessary for stand- propriate land use practices, the coasts of term sea-level trends recorded at the Tarawa ardization because of periodic and apparent undeveloped outer islands are also crum- SEAFRAME station from 12 months after its secular trends in sea level, that is, a non- bling into the sea. Events like these provide installation. periodic tendency of sea level to rise, fall or a powerful confirmation that global warm- During this period, four El Niño events remain stationary with time. Technically, it ing is not just a distant threat but it is under- took place, including a very severe one dur- is the slope of a least-squares line of regres- way, with dire implications for the Pacific ing 1997/1998 which generated a significant sion through a relatively long series of sea- people (www.wikipedia.org, 2007). sea-level drop in the Kiribati region. The usual level values. For this reason, the Australian According to McCracken of the US Global positive (rising) sea-level trends dropped to project is set to run in four’ five-year phases, Change Research of global warming, a one negative (falling) values for several months for a total of 20 years for the whole project. centimetre rise in sea level can consume one as a result of El Niño. Figures 3(a) and 3(b) The project is in its final phase now. metre or more of beach width towards the show the barometric pressure and sea-level sea (Moore, 2002). Kench and Cowell (2002) anomalies. It clearly indicates the inverted Possible impacts of a rise have provided some very useful informa- barometric pressure effect on sea level dur- in sea levels tion about how low-lying atolls respond ing the 1997/1998 El Niño. It should be noted that the early part of The primary impacts of sea-level rise are to changes in sea level. In particular, they the trend line was not stabilized due to the generally the inundation of low lands, exac- use sediment transport modelling to dem- short data length for the statistical analy- erbation of coastal flooding and erosion, onstrate how these coasts are unique in sis calculation. But it shows that the esti- intrusion of salt water into rivers and under- their response to sea-level rise. They show mates are becoming progressively smaller ground aquifers, changes in sediment depo- how sediments on low-lying atoll islands in magnitude and the lines are becoming sition patterns and a decrease in the amount could be rolled over towards the , smoother and stable. Very high trends in of light reaching the sea floor. rather than the general textbook examples 1995 and low trends in 1996 are too mis- Over the past decade, numerous vulner- of sandy beaches that show a simple read- leading to make any scientific conclusion. ability assessments have been undertaken justment of the beach profile. Sediment The length of the data is approximately a in the Pacific island countries. Harvey and transport models were used to provide Mitchell (2003) indicated that while there has been considerable monitoring of coastal 50 change in the Pacific, the timing, purpose and results of these studies vary consider- 25 ably. Most are unequivocal in highlighting 0 1994 1996 1998 2000 2002 2004 2006 2008 the extreme physical, social and econom- (mm/yr) -25 ic vulnerability of these islands and their Year people. While erosion is widely cited as an Sea-level trends -50 impact of sea-level rise, few studies have Figure 2. Sea-level trend diagram for Kiribati. (Note: trend values calculation started only after 12 204 provided quantitative assessments of the months of data were collected.) Sea level in the Kiribati Area Weather – August 2009, Vol. 64, No. 8 205 . (2001) indicate that . (2001) indicate is defined as the arithme- et al mean sea level Due to this complex combination of sev- combination this complex Due to (1999), mean sea Pittock to According The The tic mean of hourly water heights observedtic mean of hourly water Shorter period. series are the 18.61-year over specified in the name as monthly mean sea (Rockville, mean sea level yearly and level is that sea point here 1989). A noteworthy com- of the complicated is the result level such as: (i) daily tides, bination of influences effects (atmospheric (ii) meteorological evaporation, precipita- and winds, pressure expansion tion), (iii) thermal effect (volume melting global warming, due to of water (iv) seismic activityland ice), (underwater earthquake, tsunami), (v) oceanographic Kelvin waves, waves, Rossby effects (El Niño, and (vi) vertical land etc.) density changes, movement. trends sea-level long-term eral influences, at a given accurately cannot be predicted has been the main reason This location. in the Project setting up the Australian for and the sea level monitor to region Pacific Based trends. sea-level accurate calculate to a simple projection for trends, on reliable planning and be made for may the future policy-making purposes. with some regional is expected rise, to level per year millimetres ten up to by variations, preliminaryThe 2100. beyond until well of Shum results the twentieth-century rise in the sea-level This was 1.7 ± 0.1mm per year. Ocean Pacific et al. et al. Looking at the sea-level trends with time trends Looking at the sea-level Before discussion proceeds, it is important discussion proceeds, Before is. understand what the mean sea level to Can sea level be predicted sea level Can accurately? (2000) stated that the acceleration assess- that the acceleration (2000) stated industrialization over worldwide ment from be very appears to centuries the last two identi- of the trends acceleration The slow. is extremely small, fied in their exercise just five especially when it is taken from long data sets. available real danger may be if the rate of sea-level sea-level of be if the rate danger may real main question The with time. rise increases rise has accel- of sea-level find if the rate is to past. If that is the case, in the recent erated and Pacific danger is getting closer, the real find a new land in islanders might need to out their future. live which to that obvious 2, it is quite in Figure shown or less horizontal more Kiribati are for trends the length of data once 2001, that is, since calculation and away trends for is stabilized effects of the 1998 El-Niño-the severe from It clearly indicates drops. sea-level related been rise has not of sea-level that the rate What must past. recent in the accelerating be acknowledged at this stage is that there in sea- of acceleration is no clear evidence of the last cen- the course over trends level tury data available on the long-term based Mitchell precisely, More elsewhere. Figure 3. (a) Barometric pressure anomalies to September 2008 (hPa). (b) Sea-level anomalies to September to September anomalies 2008 (m). 2008 (hPa). pressure 3. (a) Barometric Figure Sea level has been rising for a long time, a long time, has been rising for Sea level Table 1 Table Kiribati situation in the for the sea-level area. parameters Significant Parameters of dataLength trendSea-level rise Sea-level land movementVertical Number of El Niños Values 16 yrs ~+0.2mm/yr + 3.9mm/yr ~ 6.14cm 4 sea level] [slightly reducing Not significant months the previous small change from Very Comments Not long enough yet the last 16 years For Including and prolonged one that was very severe long before the global warming issue was long before is not issue sea-level-rise The introduced. The in our daily lives. a new problem really period of 16 years, with some significant with some significant period of 16 years, fluctuations no longer show- in the trends It gauges locat- that the ing. must be noted in guides, wave the equatorial ed close to particular bound- the western those near to substan- also undergo may ary Pacific, of the tial fluctuations the El Niño during Southern the of Analysis episodes. Oscillation (ENSO) the National data by of sea-level 16 years that the 2008) showed (NTC, Centre Tidal rise in the Kiribati of sea-level region rate (as at September 2008). is 3.9mm per year value is very The stable; the variations from minimal and as months are the previous local value The small as 0.1–0.2mm per year. than times larger three is approximately The of 1–2mm per year. the global average in Kiribati sea level has risen approximately 1992. If December this trend 6.14cm since in the land loss will be significant continues, surveying The data also shows next years. 50 the the verticalthat for land movement, 2.19mm has risen by SEAFRAME station area the rate Accordingly, the last 11.5 years. over and there of rising land is ~+0.2mm per year impact is no significant on the sea-level-rise of the rate although it is reducing trends 1 summarizes Table rise slightly. sea-level and highlights the critical values of sea-level issues in the Kiribati region. analysis is based on tide-gauge data with example, the seismic jolt that unleashed the Environment Programme, Ministry of records of 50 years or longer. Using multiple deadly Solomon Islands tsunami on 2 Environment and : . altimeter measurements, it is estimated that 2007 lifted an entire island – Ranongga IPCC. 2007. Climate Change 2007: The physi- the sea-level rise for the Pacific Basin during – three metres out of the sea. This is just a cal science basis. Summary for policymakers. 1985–1999 was 2.4 ± 1.5mm per year, which seismic effect alone. Cambridge University Press: Cambridge. compares well with tide-gauge data analysis Although the prediction of future sea Kench P, Cowell P. 2002. Erosion of low- during the same time, 2.1 ± 0.3mm per year. level is impossible, the main component lying reef islands. Tiempo: Global Warming Hay et al. (2003) presented a simple of sea level, namely daily tides, can be pre- and the Third World 46: 6–12. method for computing local projections dicted quite accurately. However, the local Lefale P. 2007. Islanders are resilient: of mean sea-level rise for the future. To sea-level trends at any particular island are Expert. The Fiji Times, , Fiji, 14 April 2007. determine the practical implications of liable to be quite different from global and Mitchell W, Chittleborough J, Ronai B, the projection of global sea-level rise in regional sea-level trends. Sea level in the Kiribati Area in the Kiribati Sea level Lennon GW. 2000. in Australia particular islands and coastal , it and the Pacific, in Proceedings of the Science is necessary to include both global and Component: Pacific Islands Conference on local components. They did an estimate Conclusions Climate Change, Climate Variability and for – also known as Christmas Erosion is not the only issue in the low- Sea Level Rise [Linking Science and Policy]. Grezchnik M, Chittleborough J (eds). Island – which is part of Kiribati. The island lying Pacific islands due to the rising sea. National Tidal Facility: Adelaide. pp 47–57. has the greatest land area of any coral atoll Inundation, both permanent and tempo- Moore CA. 2002. Awash in a rising sea. in the world with 642 km2 and it comprises rary, will penetrate increasingly further International Wildlife 32(1). Available over 70% of the total land area of Kiribati. For inland. According to Nunn (2001), on those online: www.nwf.org/internationalwildlife/ the period between 1990 and 2050, a rise in low-lying coasts made entirely from perme- article.cfm?articleId=15&issueID=3 Kiritimati is most likely to be 10cm, but there able rocks – be they consolidated or uncon- NTC (National Tidal Centre). 2008. is also a 20% chance of it exceeding 18cm solidated, bedrock or sediment – saltwater Monthly Data Report: September 2008. South Pacific Sea Level and Climate and a 20% chance of it being less than 4cm. intrusion into groundwater will become an Monitoring Project: Adelaide. Weather – August 2009, Vol. 64, No. 8 64, No. Vol. – August 2009, Weather increasing problem as sea levels rise. It is to be noted that the SEAFRAME station Nunn PD. 2001. Sea-level changes and is located in Tarawa, and In this paper, nearly 16 years of sea-level their effects on tropical Pacific Island is approximately 3400km away. It is not data from the Australian Project was ana- environments: the next hundred years. realistic to compare the trend values from lysed and the sea-level trend for Tarawa was in Proceedings of the Science Component: SEAFRAME stations and make the above a rise of 3.9mm per year (up to September Pacific Islands Conference on Climate Change, Climate Variability and Sea Level prediction. 2008), a total 6.1cm sea-level rise for the Rise [Linking Science and Policy]. Grezchnik According to the latest Intergovernmental area. If this rate continues, loss of land will M, Chittleborough J (eds). National Tidal Panel on Climate Change (IPCC) Summary be significant in the next 50 years. Facility: Adelaide. pp 59–62. for Policymakers (2007), the following can While there is always likely to be debate Pittock AB. 1999. Assessing risk to the be noted: over the scientific accuracy of sea-level Pacific Island states from climate change trends and the length of data used, Pacific and sea level rise, in Proceedings of the • The estimated rate of sea-level rise Third SPREP Meeting on Climate Change islanders cannot wait indefinitely to see and Sea Level Rise in the South Pacific based on thermal expansion of water, more accurate sea-level-rise results. It is still Region. Kaluwin C, Hay JE (eds). South melting of glaciers and ice caps, possible to address some of the uncertain- Pacific Regional Environment Programme: Greenland ice sheets and Antarctic ice ties related to sea-level monitoring; a better Apia. pp 167–187. sheets is 1.1 ± 0.5mm per year between understanding of island change is needed Rockville MD. 1989. Tide and Current 1961 and 2003 and 2.8 ± 0.7mm per to make a better plan and policy for the Glossary. NOAA (National Oceanic year between 1993 and 2003. It indi- and Atmospheric Administration), US individual needs of each island. According Department of Commerce: Washington DC. cated that the rate was faster during the to Lefale of the New Zealand Met Service, last ten years. Shum CK, Zhau CY, Tseng HZ, while travelling around the Pacific he found Woodworth P. 2001. 20th century sea • The observed rate of sea-level rise that people were not pessimistic. They are level change in the Pacific Basin, in was 1.8 ± 0.5mm per year between resilient and prepared to adapt to changes. Proceedings of the Science Component: They have been doing it for generations and Pacific Islands Conference on Climate 1961 and 2003 and 3.1 ± 0.7mm per Change, Climate Variability and Sea Level year between 1993 and 2003. they will continue to do so (Lefale, 2007). Rise [Linking Science and Policy]. Grezchnik M, Chittleborough J (eds). National Tidal • Whether the faster rate for 1993 to Facility: Adelaide. pp 83–88. 2003 reflects decadal variability or Wikipedia. 2007. List of places on land an increase in the longer term trend with elevations below sea level. Wikipedia is unclear. There is high confidence References Foundation Inc., available online that the rate of observed sea-level rise Flannery T. 2005. The weather makers: The www.wikipedia.org increased from the nineteenth to the history and future impact of climate change. twentieth century. The Text Publishing Company: Melbourne. Harvey N, Mitchell W. 2003. Monitoring • The total twentieth century sea-level sea-level change in . Tiempo: Global rise is estimated to have been 17 ± Warming and the Third World 50: 1–6. Correspondence to: Awnesh Singh, 5cm. Hay JE, Mimura N, Campbell J, Fifita Physics Division, University of the South S, Koshy K, McLean RF, Nakalevu T, This new report suggests that global Pacific, Laucala Campus, Private Bag, Nunn P, de Wet N. 2003. Climate vari- Suva, Fiji. warming is ‘very likely’ man-made, this ability and change and sea level rise in the being the most powerful language used Pacific Islands region: a resource book for Email: [email protected] by the world’s leading scientists. However, policy and decision makers, educators and © Royal Meteorological Society, 2009 other stakeholders. South Pacific Regional these values may change abruptly. For DOI: 10.1002/wea.396

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