Currents:
Tides:
Currents:
The
currents of the Addu Atoll are notorious for their strength.
The exposure of the Maldives to the vast Indian Ocean
ensures that an immense body of water is constantly flowing
across the plateau on which these atolls are built. Oceanic
currents are largely influenced by the by the direction of
the trade winds and are of great strength. Currents in
channels near the Atoll' have been recorded at four knots or
more. Inside the atolls, current speeds are more settled and
leisurely dive are more the norm. Tidal currents, which flow
according to the height of the tide and direction of the
prevailing winds, are said to be weaker than the oceanic
currents, though they cause velocity variations in the flow.
On the eastern side of
Atoll, currents predominantly
flow into the atoll when the
northeast monsoon. The
opposite applies to the western side of the atoll. This is
by no means the rule, as changes in the wind direction and
tides can offset the influence of the oceanic currents. If
the winds ease off for a few days, then currents are more
likely to flow both in and out of the channels.
During the transitional month of April and November, when
the wind direction and oceanic currents are less
predictable, current is more likely to be influenced by the
tides and similarly flow both in and out of the channels. At
atoll passages, current streams can be quite irregular due
to the islands, reefs and sandy shoals. Most Dhoani captains
show great skills in reading the direction of the current
and take great pride in the their knowledge of the ocean.
Usually
they can tell the current direction by the tiny wave
patterns on the surface. I there is no wind, the current
forms ripples the bend around stationary objects, like the
reef, in the direction of the flow. If the current is
flowing against the wind, then the surface appears choppier
than if the current is flowing in the same direction as
wind. It is always advisable for the dive master to enter
the water and check if in doubt. It is better to be sure,
and dive on the best point, than miss the point altogether.
Top
Tides:
For divers
the effect of tides is important as they can determine the
strength and direction of currents and make shallow water
navigable. Slack water at high or low tide is the easiest
time to dive, but not necessarily the best. Depending
on the season, divers can take advantage of a rising tide
and clear water flowing into the atoll to make, for
instance, a drift dive through one of the channels.
Spring tides occur between one and three days after a new or
full moon and neap tides occur just after the first
influence of the sun and moon are working against each
other, resulting in a minimal tide range. The approximate
times between successive high tides is 12 Hrs 25 minutes
and the interval between spring and neap tides is about 7
1/4 days.
During spring tides, the range is between about 88cm and
110cm and during neap tides the range can be as little as a
few centimetres. Variations of just a few centimetres can
make an immense difference to the strength of the tidal
currents.
The height of the tide is also affected by the weather.
Winds from different directions influence the raising and
lowering of the water level and situations of high sea level
on the outside of the atoll are caused by storm surges and
wave set-up. The water also stands higher with a low
barometer, to what extent is uncertain.
The times of low and high water must not be considered to
coincide with the times of slack water and change of current
direction. Inside the atolls, water often runs in and out
long after the tide has turned. Precise and long term data
on tidal range and patterns of flow do not exist.
