The island sea level charts are drawn from monthly data from the South Pacific Sea Level and Climate Monitoring Project. I've included a chart for a second Fiji station, and also one at the end for a New Zealand station, Jackson Bay (South Island). Neither is part of the project, but data is provided on the website.
The high resolution SEAFRAME (Sea Level Fine Resolution Acoustic Measuring Equipment) monitoring stations comprise modern integrated housings which measure and record sea level, barometric pressure, water temperature and air temperature. Most of the stations were installed in 1992 and 1993, though a few were later. It's important to note that the effect of local land movement is eliminated from sea level data:
The Continuous Global Positioning System (CGPS) network monitors vertical movement in the earth's crust, such as subsidence or tectonic shifts, at the SEAFRAME tide gauges and adjacent land. Sea level data can then be adjusted to compensate for the earth's movement to within a millimeter, enabling the absolute sea level to be determined.I have voiced criticism of Australia's Bureau of Meteorology on various topics in the past, but as far as the presentation of sea level data is concerned, I rate their National Tidal Centre as the best. The page I linked to above has a table of the 12 stations in the project (and the two others I mentioned) which links to PDF plots and data tables for sea level, barometric pressure, water temperature and air temperature. The data tables in turn link to online graphical plots and text files for easy import to spreadsheets. A map links directly to the data tables. I liked that Idea so much I've pinched it for use here.
What should be evident from the plots is that any generalisation of the situation over this wide area is invalid. Apart from an almost universal downward spike during the 1997/98 ENSO event, the history and trends differ widely. It should also be clear that claims of "25 mm/year" or "no rise" since the early 1990s are also invalid.
Most of the charts are dominated by a downward "spike" in 1997/98. The level drop was due to unusually high barometric pressure during the 1997/98 ENSO ("El Niño/La Niña-Southern Oscillation") event. The correlation is well illustrated for the Marshall Islands (Majuro Atoll), so I've placed this first. Kiribati and Tuvalu have been given much attention in the news media and on the 'net recently, so they're listed next.
Readers are welcome to reproduce any of the plots - all I ask is that attribution be given, preferably with a link to this post. I haven't used thumbnails - right-click on the image and select "save image as" or whatever your browser prompts.
Level data has been converted from metres to millimetres to overcome loss of precision in Excel's trend data. Gaps in the plots indicate gaps in the original data. Note that the trend slope is monthly - multiply by 12 to get the annual value (e.g. y = 0.2269x gives 2.7228 mm/year).
Select a location from the map to view a graph of the monthly sea level statistics for that location. Click on the bottom of the blue area for the NZ station, Click on your browser's back button to return to the map.
|Source: Bureau of Meteorology|
Marshall IslandsIsland: Majura Location: Uliga
Note the 1997/98 ENSO "spike" and the correspondence with the abnormally high atmospheric pressure from late 1997 to late 1998 shown in the barometric pressure plot below:
KiribatiIsland: Tarawa Location: Betio
The trend line is pulled down by the ENSO dip from the end of 1997 to end 1998. To give an better view of the trend from 1992 to present, I replotted the chart with that data excluded:
A downward trend is evident from end 2001 to present:
TuvaluAtoll:Funafuti Island: Fongafale
As with Kiribati, the deep ENSO dip in 1997/98 pulls the trend line down on the left; it's below the 1994/1997 average. A zero trend is evident from 1999 to present:
Papua New GuineaIsland: Manus Location: Lombrum
Here's a clearer view of the 1999-2011 trend of 3.4 mm/year, slightly above the global average:
Solomon IslandsIsland: Guadalcanal Location: Honiara
VanuatuIsland: Efate Location: Port Vila
The big 1997/98 downward spike evident in most of the other plots is absent; instead there's a relatively steady upward trend.
FijiIsland: Viti Levu Location: Lautoka
Island: Viti Levu Location: Suva
TongaIsland: Tongatapu Location: Nuku'alofa
Although there's a steep trend from 1993, current levels are not dissimilar to those between 2000 and 2003.
Cook IslandsIsland: Rarotonga Location: Avatiu
Levels seem to have stabilised from 2006.
SamoaIsland: Upolu Location: Apia
The familiar ENSO dip pulls the trend down at the LHS, but there is a sharp upward "spike" from 2010.
NauruIsland: Nauru Location: Aiwo
Federated States of MicronesiaIsland: Pohnpei Location: Dekehtik
An overall upward trend, though little change from 2007 to present.
New ZealandIsland: South Island Location: Jackson Bay
There seems to be little overall change from mid-1998 (after the ENSO dip) to present. A plot from 1999 confirms that: