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==Explanation==
 
==Explanation==
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In this comic, [[Randall]] seems inspired by the timing of {{w|ocean current}}s, much as he has previously been with [[2805: Global Atmospheric Circulation|air currents]], although he may even have already considered some of the technicalities [[1675: Message in a Bottle|prior to that]]. As supporting evidence, he provides a DOI reference to a 2016 Jönsson & Watson open-access article in Nature Communications, '[https://www.nature.com/articles/ncomms11239 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.
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{{incomplete|Created ten years ago by a WATER CURRENT - Please change this comment when editing this page. Do NOT delete this tag too soon.}}
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In this comic, [[Randall]] seems inspired by the timing of {{w|ocean current}}s, much as he has previously been with [[2805: Global Atmospheric Circulation|air currents]], although he may even have already considered some of the technicalities [[1675: Message in a Bottle|prior to that]].
  
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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 ''{{w|Ship of Theseus|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.
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The DOI Jönsson & Watson reference is to a 2016 open-access article in Nature Communications '[https://www.nature.com/articles/ncomms11239 The timescales of global surface-ocean connectivity]'.
  
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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 {{w|Weddell Sea}} it may take decades. The Weddell sea lies near the {{w|Antarctic Peninsula}}, part of the {{w|Southern Ocean}} whose circulation can be considered largely isolated from the neighbouring bodies of water by the {{w|Antarctic Circumpolar Current}}. In particular, that area contains the {{w|Weddell Gyre}} one of the two {{w|ocean gyre}}s in that area.
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The idea here is that water dumped into the ocean today will take ten years to circulate round to the next coastline (wherever that is). So you can plan ahead before posting water to someone...
  
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The title text also mentions {{w|inland sea}}s, 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 {{w|Mediterranean Sea}} which is only connected to the {{w|Atlantic Ocean}} through the narrow {{w|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 {{w|evaporation}} and re{{w|precipitation}}) into its catchment area) and thus they can only ever circulate back to the dumping point (deemed 'undeliverable').  
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The title text mentions that if it is "Same-ocean delivery" it may only take a few years as the coast lines are in the same general body of water, and doesn't have to pass around large obstacles like continents or through small gaps.
  
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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.)
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But if you wish delivery from {{w|Weddell Sea}} it may take decades. This is not only because it lies near the {{w|Antarctic Peninsula}}. You might wish delivery to a nearby oceans coast... But also because it contains the {{w|Weddell Gyre}} one of the two gyres that exist within the {{w|Southern Ocean}}. An {{w|Ocean gyre}} is any large system of circulating ocean surface currents. So any water dropped there would likely end up circling there for much longer than water dropped in any particular other part of an ocean where there is no gyre nearby. For certain it has been [[Randall|Randall's]] intention that we should all end up reading about Ocean gyre.
  
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The {{w|Caspian Sea}} is a real inland sea that has no outlet to any oceans and only inlets from rivers, one of a number of [[2325: Endorheic Basin|endorheic basins]] that are also {{w|Endorheic lake|lakes}}, and thus trivially isolated from all other maritime currents.
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The title text also mentions {{w|Inland seas}}, which is bodies of water that are very large in area but is either completely surrounded by dry land or connected to an ocean only by a river or a strait. He mentions the {{w|Mediterranean Sea}} which is only connected to the {{w|Atlantic Ocean}} through the narrow {{w|Strait of Gibraltar}}; therefore, water molecules dumped in one ocean would not get to those oceans (except perhaps by {{w|evaporation}} and {{w|precipitation}}). And thus they are returned to sender as undeliverable.
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The Mediterranean Sea is not completely cut off from the main oceans and the surface current is actually going into the  Mediterranean Sea, as the heavier and more salty water in the inland sea causes the water to sink below the water of the Atlantic sea. So the {{w|Strait_of_Gibraltar#Inflow_and_outflow|outflow}} from the sea is far beneath the surface. So actually it would be water dumped in the Mediterranean Sea that would never leave the ocean as surface water!
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The {{w|Caspian Sea}} is a real inland sea that has no outlet to any oceans and only inlet from rivers.
  
 
==Transcript==
 
==Transcript==

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