Chapter I Intro & Objectives - SPREP

PHOENIX ISLANDS PROTECTED AREA MANAGEMENT PLAN
Chapter III. Background, 1. Physical Setting of the Islands
Draft 1 March 2007
thickness (ULT) estimates improved through iterations and were eventually similar to true
upper layer thickness readings for the time series examined.
Tides – Spring tide was about 1.2 m (4 ft) (Hydrographic Office 1916). Tidal variation was
1.5 to 1.8 m (5 to 6 ft) during the full moon (Bunker 1951; ranged 1 m (3.3 ft) and spring
range was 1.2 m (4 ft) according to McIntire 1960). At other times it was 0.6 m (2 ft)
(Bunker 1951). Mean high-water interval was exactly 5 hours (McIntire 1960). McIntire
(1960) noted that slack tide was frequently only 10 minutes.
Groves (1956) reported that sea-level observations on Abariringa (Canton) showed regular
four-day oscillations that were related to equatorial waves in the easterly winds over the
island. Similar results were observed on Ocean Island. Tide gages on Butaritari and Tarawa
did not show such a regular record.
The tidal station at Abariringa (Canton) recorded unaccountable change in sea levels of 15 to
18 cm (6 or 7 inches) at 3.8 day intervals (Wiens 1962).
Using sea level records of various central Pacific islands, including Abariringa (Canton),
Wunsch and Gill (1976) calculated the spectral energy density and demonstrated that there
were higher energy levels associated with inertia-gravity wave frequencies. In Abariringa
(Canton), there was a 4 day oscillation that dominated the energy spectrum. This was not
found in higher latitudes. Wunsch and Gill (1976) compared the wind and sea level data and
found them to be statistically significantly, particularly at the 0.25 day -1 (4 day oscillation).
They suggested that the oscillation was due to oceanic resonance rather than atmospheric
resonance since oceanic resonance had higher energy.
Henderson et al (1978) installed tidal monitors in Abariringa’s (Canton’s) lagoon to monitor
and compare ocean and lagoonal tides. Results were similar. Drift cards and dye tracks were
also used to study Abariringa’s (Canton’s) lagoon. Wind-driven cards moved down-wind,
but in a complicated pattern. Some cards became entrained in small eddies.
Sea-level data from Abariringa (Canton) indicated that there was an anomalous rise in sea
level during the latter half of the 1965 El Niño year (Busalacchi et al 1983). There were great
difficulties in interpreting sea-level data at Abariringa (Canton) because of the interplay
between equatorially trapped Kelvin waves and long Rossby waves.
Khandekar et al (2005) reported that for 28 years there was no detectable change in sea level
on Abariringa (Kanton). This example was provided in the global warming debate context.
Waves/Swells - Banner and Banner (1964) noted that strong winds and surf at times rendered
collection on the outer side of the ocean reef too hazardous on Abariringa (Canton).
Environmental Data Services (1966) reported that at long intervals high sea swells occurred
several times in the past. An event was recorded in January 1958 when swells 4.6 to 6.1 m
(15 to 20 ft) high lasted over a period of several days.
Gilbert (2000) examined equatorial inertia-gravity waves for various locations in the central
Pacific, including Abariringa (Kanton). Christmas, Abariringa (Kanton), and Tarawa had
significant peaks at frequencies corresponding to first and second meridional mode inertia-
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