Just need a bit of clarification before I can provide more of an answer.
Can you say whether you are looking for data on oceanic currents or tidal streams (or both)?
And for which area? I saw you mentioned Mar del Plata, but then you talked about the channels...
Having sailed around the bottom, here's a summary of my experience.
Concerning oceanic currents, in addition to the sources already mentioned, I would add Navimail: send the following content to firstname.lastname@example.org
(subject line does not matter, and adjusting the area is done with the Z line):
Z -60.000 -50.000 40.000 30.000
P courant tprof
G 24 48 72 96 120 144 168
For tidal streams, data is pretty patchy and I doubt you'll find an electronic tool (although I would love to be contradicted). Tidal streams will have to be computed from tidal heights and times. Various tools such as Marées dans le Monde generally work OK, but probably best to download official tidal tables. If I remember correctly, they should be available freely on Argentinian and Chilean hydro offices websites, but I may be mistaken.
From Mar del Plata to Lemaire Strait, that is pretty essential, given the large tidal range and corresponding currents. These will be strong mostly in rivers and estuaries and are then timed in sync with the tides. Another place where looking out is necessary is around Caleta Horno. Lots of current between the mainland and the island east of the caleta. As for the Lemaire Strait, even when calculating the tides, it can be a lottery... Essential to pick "manageable weather".
Once in the channels, things get very much softer, because the tidal range drops significantly. However, if I remember correctly, there are not many tidal prediction points on the Chilean side before you reach the area of Chiloé (big tides and currents there). For most places south, tides are almost unimportant, but in places where there are narrows, it can be wise to time your passage
accordingly. Especially important in both narrow channels leading to Puerto Natales area... The catch is to use the "E del P" data given on most chilean charts
. This is the offset between the moon crossing the meridian and the high tide. In most cases it works fine and you'll have a decent approximation of the timing, and any official prediction likely wouldn't fare better given the complexity of the channels in the area as well as other factors coming into play, such as wind
force and direction, atmospheric pressure as well as rainfall and glacier calving.
I hope this can help your friend, and I hope they actually have fun calculating all this, because it's part of the game! Plug
and play nav data down there would be too easy... (they will likely also discover the offset charts
, navigating in all white areas, with no hydrographic data in places, and guessing their way into glacier moraines!)
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