Buckets, Inlets, SST’s and all that – part 2

Since this blog has main focused on air temperature measurement, and has not done any discussion of manual measurement techniques of Sea Surface Temperature measurements, I thought it would be good to first review some of the instrumentation used.

Sea Surface Temperature Measurement Instruments:

Standard Thermometer

Standard Thermometer

Measures: Temperature in degrees, typically used in the bucket thermometer

Operates: At any depth by cable or line or by hand

Notes: Mercury in original thermometer has been replaced in many standard

thermometers by less toxic materials

Bucket Thermometer

Bucket Thermometer

Measures: Water temperature near the surface

Operates: At the surface by hand or line

Notes: Typically lowered about 1 meter into the water, left there for one

minute, and then retrieved deck side for reading.

Reversing Thermometer (for Nansen Bottle)

Reversing Thermometer

Measures: Water temperature at a specific predetermined depth

Operates: Only when turned 180 degrees (the mercury breaks in the special loop

and will not get back together until reset) Temperature at depth can be recorded

with a 180 degree flip (as is done with the Nansen Bottle) and there will be no

change on the way up.

Notes: A Nansen bottle

is a device for obtaining samples of seawater at a specific depth. It was

designed in 1910 by the early explorer and oceanographer Fridtjof Nansen.

The bottle, a metal or plastic cylinder, is lowered on a cable into the sea, and

when it has reached the required depth, a brass weight called a “messenger” is

dropped down the cable. When the weight reaches the bottle, the impact tips the

bottle upside down and trips a spring-loaded valve at the end, trapping the

water sample inside. The bottle and sample are then retrieved by hauling in the


Bathythermograph (BT)


Measures: Water temperature over a range of depth

Operates: Over any depth with a cable or line by hand or with a hydraulic winch

Notes: This model records the information inside and is retrieved however there

are expendable models (XBTs) that free fall on a copper line and transmit the

temperature and depth information through the copper wire before dropping to the


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May 30, 2008 11:04 pm

Since the 1960’s, we dropped literally hundreds of Bathythermograph bouys from maritime patrol aircraft. These relayed a temperature signal back to the aircraft where a temperature plots was traced on a graph. We used these to plot “ray path diagrams” to calculate sound travel in the water in aid of tracking submarines. All the records went ultimately “up the chain”, so it would be nice to know where those records are as they would provide a bit more history and fill in some of the gaps. I know Canadian records were handed to the Russians as part of an international study – and that was during the Cold War…

May 31, 2008 1:19 am

interesting sharp dip in global temps lately
REPLY: Thanks Rex, I had not looked in awhile. I’ll showcase this soon.

May 31, 2008 1:20 am

anybody know what happened to COLA maps?

Tom in Florida
May 31, 2008 5:06 am

Sea water surface temps can vary quite a bit at any particular spot depending on cloud cover, humidity, time of day, wave action, precipitation, upwelling conditions, currents and the previous days weather conditions. Unless all this was recorded at the time, each and every time, we simply have an isolated snap shot of a few cubic feet of water.

May 31, 2008 6:05 am

me too, would certainly know what happened to all the bathytermograph datas we got 24/7, every four hours on all Navy vessels.
Personally, I did it in the 70ties on a Federal German Navy ship, from Barents Sea down to Gibraltar, from mid Atlantic to the east of Baltic sea, SST to temperatures downto 50 meters sub surface.
As far as I know, it was common procedure by all NATO vessels.
All these datas could be a treasure for getting the real.

May 31, 2008 6:40 am

Charles Blow at the New York Times is tardy with some ignorance about AGW and tornadoes. Blow, blow, blow ye winds, blow.

May 31, 2008 7:41 am

Hmm. Didn’t you leave out the predominant means of measuring sea water temperature in the latter half of the twentieth century– the sea water intake temperature?
I served on aFletcher class destroyer. My memory is hazy, but I seem to recall an intake pipe about 18″ in diameter (though that may have been after it was split). The principal use of sea water was in the steam condensers.
More importantly it was located well below the waterline, at least sufficiently deep so that heavy weather would not expose the inlet.
I am not sure why sea water say 10′ in depth can be presumed to be the same temperature as water retrieved by a bucket on the surface.
REPLY: Your last line says it all, and I have plans to discuss that in part 3, and maybe part 4 if I have enough material.

jerry bono
May 31, 2008 8:33 am

Maybe this is in the literature I don’t know since I have not read it but it seems to me all the bucket data came from right on the surface of the ocean, the real interface between air and sea. Now, how deep was the sample taken from the engine inlets. I know it depends on the size of the ship but it should be deep enough to get away from potential wave troughs, maybe say 10 feet? I don’t know. From my scuba diving experiences I can tell you that I have felt some very sever thermal gradients. Most of this was near the cost obviously and I would expect open ocean to to be less variable but there should be a variation.

Jon Jewett
May 31, 2008 10:49 am

I am a retired merchant marine engineer. I made my living on merchant ships from 1966 to 1999, when I retired as Chief Engineer of a 32,000 SHP steam turbine powered container ship.
A ship moves through the water at between 12 knots and 22 knots. (Twelve knots for an old Liberty Ship from WWII, 22 knots fairly representative of new ships.) At even 12 knots, the speed is fast enough to cause turbulent flow of the sea water and thereby prevent a “warm” layer forming along the ship. In addition, very little of the ship is a significant heat source; only the area in way of the machinery spaces. Most of the ship is thermally inert cargo space that may be warmer or colder than the sea temperature. The main cooling water pump (Main Circulator) takes suction through the hull at a depth of 15 feet to 60 feet (depending on the ship) below the surface of the water. In addition, a Main Circulator will pump up to several thousand gallons per minute.
In short, the concept that the water would be heated by a measurable amount is far fetched at best. The statement indicates that assumptions were made about the measurement process and there was no meaningful investigation before these opinions were voiced.
Actually, there is cause for concern in using these numbers. Typically, either alcohol type bulb thermometers or bimetallic type thermometers were used. They were calibrated at the factory before they were installed, but never after that as long as the readings were “close enough”. It was not until the late ‘60s that thermo-electronic (e.g. RTD and Thermister) methods started to enter the fleet. It is to be expected that, particularly with the older readings, each one may be on the order of up to 10 degrees off, with a random distribution.
Steamboat Jack

Chance Metz
May 31, 2008 5:38 pm

Wow took about messed up readings!

May 31, 2008 7:34 pm

The following PPT mentions uninsulated buckets before WWII and insulated buckets after. Was Britain behind the times and using uninsulated ones later?

Chance Metz
June 1, 2008 4:52 pm

No suprise if they were.

June 2, 2008 4:58 pm

For intake thermometers from 10-50 ft below the surface, one significant question would be how much of the water may actually be surface water that has been deflected downward, so a 20 foot deep inlet may be sucking water that was, say 8 ft deep (or whatever). It seems that would be highly specific to hull shapes and inlet port details.
I would almost guarantee that marine engineers have such data and probably for many hull shapes, and if they don’t for all hull shapes they could probably fairly easily do that with a little bit of the global warming research $ that’s floating around.
Also, the comment about surface water churn in highly traveled waters contributing to lower readings seems to make sense, in the same way that a hurricane leaves behind a trail of cooler water, but I would be cautious about jumping to a numeric conclusion on this without some analysis.

June 3, 2008 7:24 am

Interesting to see manual measurement of sea surface.

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