Re: Kaimanawa Wall once again...

From: Eric Stevens (eric.stevens_at_sum.co.nz)
Date: 09/05/04 

Date: Sun, 05 Sep 2004 17:29:19 +1200

On Sun, 5 Sep 2004 13:28:40 +1200, Alan Brennan <the.c@in.the.hat>
wrote:

>On Sun, 05 Sep 2004 11:22:37 +1200
>Eric Stevens ( eric.stevens@sum.co.nz )
> wrote
>
>> On Sat, 4 Sep 2004 23:03:35 +1200, Alan Brennan <the.c@in.the.hat>
>> wrote:
>>
>> >On Sat, 04 Sep 2004 12:45:59 +1200
>> >Eric Stevens ( eric.stevens@sum.co.nz )
>> > wrote
>> >
>> >snip
>> >
>> >> >1.The currents and winds go the wrong way.
>> >>
>> >> Not so. See the diagram at
>> >> http://www.uwm.edu/Course/416-340/lecture_notes/03PhysicalGeog2003.html
>> >> The trade winds are easterly in the tropical belt. The surface
>> >> currents follow them.
>> >
>> >snip
>> >
>> >That is a pretty simplistic answer. Of course the water flowing Eastward
>> >must move Westward again unless it is to all pile up on the South
>> >American beaches. But it is a three dimensional system, and no, the
>> >currents do not necessarily follow the trade winds.
>>
>> The surface currents do tend to be driven by prevailing winds but the
>> deep return currents are another matter. See
>> http://www.geo.cornell.edu/geology/GalapagosWWW/GalapagosClimate.html
>> >
>> >"Huge whirls, formed by the major ocean currents, are found roughly
>> >north and south of the equator; the Equatorial Counter Current separates
>> >them. The northern whirl is formed by the North Equatorial Current,
>> >Japan Current, North Pacific Drift, and California Current; the southern
>> >whirl is formed by the South Equatorial Current, East Australian
>> >Current, West Wind Drift, and Peruvian (or Humboldt) Current. There are
>> >many branch and feeder currents that help to constantly circulate ocean
>> >water of differing temperatures and salinities."
>> >
>> > Your primary school diagram of the trade winds is irrelevant. Try
>> >looking at
>> >http://facs.scripps.edu/surf/sepa.html
>> >This is a map of wave directions: ie how things floating on the surface
>> >actually move. Try explaining how a potato floating on the water off
>> >South America will reach New Zealand.
>>
>> Its a mape of wave directions at a particular time. While the waves
>> are driven by the winds of the day, the global circulation pattern of
>> the atmoshere arises from the Hadley cells of diagram I cited above
>> and the long term trends are as I described them. If you doubt me or
>> want more detail, consult any ocean cruising guide.
>
>But we're not talking about the global circulation patterns of the
>atmosphere, we're talking about the global circulation patterns of the
>oceans.

What do you think drives any of the surface currents? Are you really
arguing that they are not affected by the prevailing wind?

See http://www.es.flinders.edu.au/~mattom/IntroOc/notes/lecture02.html

  "The prevailing wind system is the major driving force for ocean
    currents".

>You know. Big wet thing. Blue. Sits *under* the atmosphere and
>is affected by it so some degree but only to some.
>If you are wanting the sort of rough and ready diagram you seem to have
>a penchant for, take a look at
>http://www.physicalgeography.net/fundamentals/8q.html

You should have read it. You would then have noticed that the opening
lines are:

   "Ocean currents are driven by the circulation of wind above surface
     waters. Frictional stress at the interface between the ocean and
     the wind causes the water to move in the direction of the wind".

>which is a rough and ready diagram of the *ocean* currents.

You really didn't read it. The diagram is titled:

   "Figure 8q-2: The following illustration describes the flow pattern
    of the major subsurface ocean currents. Near surface warm currents
    are drawn in red. Blue depicts the deep cold currents. Note how
    this system is continuously moving water from the surface to deep
    within the oceans and back to the top of the ocean".

Note the words 'subsurface'
.
>But lets all take a deep breath here. The original question was whether
>kumera could self seed into the Pacific by means of the ocean currents.
>I say no. So does anyone else who knows anything about ocean currents or
>kumera. You are arguing otherwise? Unless you actually want to defend
>that proposition, or argue that the kumera blew here on the westward
>flowing tade winds let's leave Hadley cells, coriolis forces, polar and
>subtropical gyres, El Nino, salinity ratios and surface friction stress
>differentials quietly gurgling away doing their thing, shall we?
>>
I merely corrected your erroneous argument as to the direction of the
wind. You can do what you like with the kumara. :-)

Eric Stevens

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