13 October 2008

2009 tide tables are out!

I've just got 2009 tide tables today! And thus, planning for next year's shore explorations.
Here's some highlights of the 2009 tides, and more about low tides in Singapore.

Highlights of the 2009 tides
  • There's no low tide during Lunar New Year 2009! Rather odd. Since I first started visiting the shores in 2001, there has always been a low spring on LNY eve and the first two days of the New Year. And they were a good excuse to be anti-social and avoid pesky visiting.
  • There are extremely low evening tides until March. Unusual. In the past, these very low tides usually only happen in the morning.
  • We get to rest in March. There's virtually no spring tide the entire month.
  • The first predawn spring low trips start end April and lasts until August. So best to enjoy sleeping while we can. Once the morning lows start, it's back to jet-lag 4 hours of sleep a day.
What's the big deal about low tides
Isn't there a low tide every day?
Yes, it's true, there is a 'low' tide every day. But a 'low' tide can be anything from 1m to -0.1m, yes, that's MINUS zero. To understand why this is so, let's start with the basics.

What causes the tides?
A whole bunch of stuff can affect tide height. But three main things are behind the tides
  • Gravitational pull of the moon
  • Gravitational pull of the sun (although much further away, the sun is gianormous)
  • The rotation of the earth (the way your laundry in a spinning washing machine moves outwards)
When the moon and the sun are lined up, their effects are combined resulting in a higher high tide and a lower low tide. This is called a spring tide because the water appears to spring up more rapidly than usual. Thus spring tides happen around a new moon (moon is just a thin cresent) and a full moon.

At other times (i.e., quarter moon), the effects of the moon and sun are not combined so there is a smaller difference between the high and low tide. This is called a neap tide.

There's an animation of this on the NOAA website, and a very 'cheem' explanation on the wiki on tides.

What's so special about a low spring tide?
During a super low tide, we can get a quick glimpse of a part of the shore that is seldom exposed. Also, usually a larger area of the shore is exposed, since the low tide is a lot lower. So there is more to see in terms of variety and area uncovered. But remember the 'spring' part of this low tide: so the tide moves fast and the window of low tide is usually short, about an hour at most.

Guided walks on our shores are usually held during low spring tide. If you go during a not so low tide, there isn't as much to see. Although there is always something to see on our shores at any tide. For example, stuff clinging to rocks, coastal plants, birds and more. See the Adventures with the Naked Hermit Crabs blog for some sightings during their free Chek Jawa boardwalk tour which is conducted at any tide.
Natural cliffs of Sentosa
In this photo of the natural shore of Sentosa at low spring tide, you can see the mid-water mark as the dark portion on the natural cliffs. The area exposed at low spring tide is quite different from that at higher tides. It can also be dangerous to go at the wrong tide, or to be unaware of the turning tide as you might get trapped. Especially on a shore such as this one.

Not all shores can be visited at the same tide level. Some shores in Singapore require lower tides than other shores for a safe and enjoyable visit. It's thus important to go with experienced people and with shore guides. You will be safer, and also see and learn more about our shores.

In Singapore, low spring tide happens before sunrise around April to August (at about 2-3am, hence the sleep deprivation), and then after sunset in October to February. Often, there are no low spring tides in September and in March.

Low spring tides don't necessarily happen on weekends.

Low tides don't happen at the same time every day. This is because the moon takes more than 24 hours to go around the Earth. So the low (and high) tide shifts by about 50 minutes every day.

The tides can differ from predictions depending on the winds (which can raise water levels) and the barometric pressure (the pressure of the miles of atmosphere on the sea level). Also, we've found, when the spring tide changes from evening to morning and visa versa, the tidal prediction can be off.

The rough tide times for Singapore is available online on the NEA website. But these are generally not detailed enough for our purposes in planning trips to our shores. To buy the tide tables, go to the MPA website for the list of retailers.

Here's some tide tables available online for some sites (provided mainly by marinas).

Here's more about tides with photos of Chek Jawa at different tide heights on the wildfact sheets on the wildsingapore website.

Here's a great post about King Tides on the The Malaria, Bedbugs, Sea Lice, and Sunsets blog by Rick MacPherson.

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