2859: Oceanography Gift

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Oceanography Gift

Title text: Shipping times vary. Same-ocean delivery may only take a few years, but delivery from the Weddell Sea in Antarctica may take multiple decades, and molecules meant for inland seas like the Mediterranean may be returned as undeliverable by surface currents.

Explanation

This explanation may be incomplete or incorrect: Created ten years ago by a WATER CURRENT - Please change this comment when editing this page. Do NOT delete this tag too soon. If you can address this issue, please edit the page! Thanks.

In this comic, Randall seems inspired by the timing of ocean currents, much as he has previously been with air currents, although he may even have already considered some of the technicalities prior to that. As supporting evidence, he provides a DOI reference to a 2016 Jönsson & Watson open-access article in Nature Communications, 'The timescales of global surface-ocean connectivity'.This would be extremely impractical, since in ten years, it's possible that you and the recipient broke connections, or one of you (or both of you) passed away. If these scenarios are not the case, ten years is an awfully long time to wait for a present.

In this specific (fictional) example, the water dumped into the ocean today will take ten years to circulate round to the depicted neighbouring coastline (wherever that is). Which implies significant planning ahead is necessary before posting water to someone. And a lot of presumption about the lack of any other dispersal/dilution, or that some degree of fungibility is acceptable, so long as it is philosophically the same group of molecules involved. Of course, some of the water molecules may take a short-cut by being evaporated then precipitated closer to the delivery site.

The title text mentions that "same-ocean delivery" may only take a few years, as the coast lines are in the same general body of circulating water, and doesn't have to pass around large obstacles (like continents) or through small gaps (straits). But if you wish delivery from Weddell Sea it may take decades. The Weddell lies near the Antarctic Peninsula, part of the Southern Ocean whose circulation can be considered largely isolated from the neighbouring bodies of water by the Antarctic Circumpolar Current. In particular, that area contains the Weddell Gyre one of the two ocean gyres in that area.

The title text also mentions inland seas, which can be generalised as bodies of water that are very large in area but either completely surrounded by dry land or connected to an ocean only by a river or a strait. He mentions the Mediterranean Sea which is only connected to the Atlantic Ocean through the narrow Strait of Gibraltar; the intention of the title text is to suggest that water molecules dumped in an ocean would not get to appear in such a sea (except by evaporation and reprecipitation) into its catchment area) and thus they can only ever circulate back to the dumping point (deemed 'undeliverable').

In reality, the Mediterranean Sea is not completely cut off from the main oceans and surface currents actually do reach into and around the Mediterranean. The natural loss from evaporation is not fully compensated for by the inflow of the incident rivers from southern Europe, North Africa and Asia, directly or via other attached bodies of water (e.g. the Black Sea). The movement of water also involves the deeper Levantine Intermediate Waters layer (a subsurface current) which exits via Gibraltar and helps to further draw current inwards at the surface level. As such, except for a limited amount of water which reverses direction within the extreme western end the Mediterranean, it is more true to say that surface currents cannot actually transport water from within the sea outwards into the Atlantic (and beyond). (This explanation ignores flow through the Suez Canal.)

The Caspian Sea is a real inland sea that has no outlet to any oceans and only inlets from rivers, one of a number of endorheic basins that are also lakes, and thus trivially isolated from all other maritime currents.

Transcript

This transcript is incomplete. Please help editing it! Thanks.

[Cueball and Megan are standing thigh deep, at either edge of a stretch of water between two steep but walkable shorelines.]

[Cueball, at the left, is apparently opening bottles of water and pouring them into the sea while recording himself.]

Cueball: Happy birthday!

Cueball: I got you these water molecules.

[Sound effects:] (click) (pour)

[The water between has a morass of short swirling arrows indicating movement. In the air above this there is a square-bracketted 'label']

[Label:] 10 years pass

[Megan, at the right, is dipping bottles into the water to fill them]

Megan: Aww, thank you!

[Sound effect:] (scoop)

[Text below comic:]

Global surface ocean connectivity times are ≤10 years (Jönsson & Watson, 2016, DOI:10.1038/ncomms11239), so if you're willing to plan ahead, you can pour water into the ocean while wishing someone a happy birthday, and then in 10 years let them know they can pick up their gift at the nearest coastline.

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Discussion

The explanation for inland seas is incorrect. What Randall refers to is that with some (or many) of them, the surface currents work against letting any water flow in, because those currents flow outward. Thus, water poured into the Atlantic won't enter the Mediterranean, but water poured into the Med will move outward and then join the general ocean exchange. What the explanation says does apply to (for instance) the Dead Sea. Of course, water molecules added to that have a high chance of evaporation, which would then get them into the global circulation anyway. 172.71.98.97 (talk) 07:04, 25 November 2023 (please sign your comments with ~~~~)

This is incorrect anyway, since the Mediterranean has a net inflow of water from the Atlantic (inflow from its rivers can't make up for evaporation). 172.70.38.34 08:20, 25 November 2023 (UTC)

I would not have called the Med an "inland sea", either.

Though I haven't read the main article/its history, since I put the very first paragraph there and invited others to add more. I presume someone took that literally (like Dead, Aral, Caspian or Salton, each with their own characteristics) rather than with the perhaps rather over-broad definition of having a single relatively narrow 'neck' connection.

But the caveat in the Title Text of undeliverable by surface waters does apply, depending upon where you're sampling, as the Levantine sink of water takes inflowing water (that hasn't reversed around Corsica and gone straight back out) and feeds it round to the depths (and out again into the Atlantic) to a large degree. If you're relying on the 2D circulation, you lose such connectivity through the depths as well as it attaining atmospheric height...

i.e. complex, and I think Randall's wording is not perfect. And yet to see if I can go back and improve/correct/support the Explanation. 172.71.178.134 18:47, 25 November 2023 (UTC)

...and, re: the later edit about the Suez, yes. That too. Meant to consider it, in my re-edit, but forgot to finish checking which way the flow was (or tended to be). Good catch, though. 172.71.94.193 15:06, 26 November 2023 (UTC)

I am not inclined to call the Mediterranean an "inland sea" either, at first thought... but upon inspection, perhaps only because Europe and Africa are separate continents, which makes it feel less "enclosed" and more of a "border", which is not a very good reason. Terdragontra (talk) 20:23, 13 January 2024 (UTC)

Well, (very-pre-)historically, it was the Tethys Ocean, before the continents started to close up like they have done. 172.69.79.139 21:09, 13 January 2024 (UTC)

Randall says that molecules intended for the Med may be returned as undeliverable - not that they will. I would read that to mean that they're more likely to end up back where they started than they are to make it to a destination in the Med, in which case the current explanation is a bit off base.172.71.242.37 09:26, 27 November 2023 (UTC)

I'm not sure the overall premise is accurate; the paper is dependent on very low probability pathways, using the ability of algae to reproduce in those regions to give billions of chances of hitting those difficult pathways. The water in the bottle doesn't reproduce. 172.69.194.70 (talk) 09:51, 27 November 2023 (please sign your comments with ~~~~)

<mumble mumble>...homeopathy...</mumble mumble> 172.71.178.32 12:00, 27 November 2023 (UTC)