# What would the Climate effects of a Circum-Equatorial current be on a world with 0 degrees of axial tilt

The basics of my worlds oceanography is that there is one large ocean that covers one side of the world completely, and in-between the northern and southern continents on the other side of the world, there is an equatorial ocean that is atleast forty degrees from it's northern to southern end, around 20 degrees on each side of the equator. What this results in is a equatorial current that goes around the world. The ocean is wide enough that continental shelf's can't cause it to break off since the equatorial ocean on the land side takes up nearly half the continent. My question is simply, how would a current that circles the world at the equator effect the climate? What would the Climate of the land nearest the equator be?

Other essential features of the world I should mention are it's star: Trappist-1, the real world one. It's axial tilt, 0°. The fact that it is the 6th planet in Trappist-1. Also, it has a day-night cycle of roughly 24 hours because of literal magic. A "week" on this world is the amount of time it takes for that planet to go around the star, (roughly 12 earth days, the world is Trappist-1g) while a month (or year, depending on the length. I haven't accurately calculated it) is the amount of time it takes for all the planets in the system to be in the same position.

There are no circumpolar currents, though the poles themselves are water.

• Can you expand on that stuff about one full orbit around the sun being one week? Is a 'week' much more than 7 days, or is this an expectionally tight orbit? how do you feel this will affect anything at 0 degrees of axial tilt? i do not get that part of the question. --- And about the equatorial current: Is that magic, or what do you feel would keep such a current going? (I assume you mean an unbroken band of water at the equator circling the globe indefinitely, tight?) Commented Oct 24, 2021 at 19:56
• I am giving every piece of astronomical information on the planet I believe might be necessary to answer the question, or atleast to understand it. I would imagine the Circum-Equatorial current would exists because there is no land or Continental shelf in the tropics on my world. A "week" is as long as the orbit of Trappist-1g, the place where the story is set, roughly 12-13 earth days. I don't know how these features affect the climate. Commented Oct 26, 2021 at 20:41
• So the 'week' and 'year' are sociologic timeframes for the Trappist people? because otherwise 1 orbit = 1 year ... --- And about the circumequatorial current : the absence of obstacles to movement does not mean that anything actually moves - do you have a proposed mechanism that feeds the current? Commented Oct 27, 2021 at 5:51
• Isn't the primary thing that causes currents to move air currents and differences in temperature and salinity? Since the planet rotates at around the ballpark of Earth's spin (it is not tidally locked), I imagine it would have winds somewhat like Earth's. But yes, a year is a sociological construct. What is normally called a year by astronomy is called a week on that world. Commented Oct 27, 2021 at 20:51

You might get a weak, wind driven, anti-rotational, surface current around the equator but without structures, read continental shelves, to deflect the motion of warmer surface water heading north/south cooling and sinking and heading back south/north along the seabed beyond the basic Coriolis deflection you won't get large scale east/west movement of water. You will get Coriolis deflected north/south current loops and interactions along the continental coastlines that will overwhelm any possible effects generated by the weak circumequatorial effect.

As a note the equatorial surface waters of this world will be hot enough that gas solution balance will be compromised. Additionally there will be no winds or currents that cross it anywhere so until someone invents technologies or magics capable of overcoming that, for an Earth sized world, ~4440km barrier of barren ocean the northern and southern hemisphere will be effectively isolated from each other.

One other thing unless the world in question is tidal locked, or you magic them away there will be a circumpolar current in any fluid, liquid or gas, at the poles. The fact of the planet's rotation causes rotational currents at the rotational poles, period.

• I was just saying there wouldn't be any circumpolar ocean currents cause there is land that would break it up at each end. I have one question though. What do you mean by "gas solution will be compromised"? Commented Nov 12, 2021 at 16:49
• @skout You said there was water at the poles, any ocean at the poles will have a rotational current. Forgot the word "balance"; water dissolves more or less of certain gases depending on it's temperature, colder water dissolves more oxygen than warmer water which dissolves more carbon dioxide. Lack of oxygen means fish and aerobic bacteria can't live in the water, excessive dissolved carbon dioxide makes water acidic and makes certain cations, like calcium, that are essential for life inaccessible to marine biota.
– Ash
Commented Nov 13, 2021 at 4:25
• So, the water of this world would consume more CO2 making the oceans less habitable and making a higher amount of oxygen in the atmosphere? Commented Nov 14, 2021 at 20:50
• @skout Carbon Dioxide tops out at hundreds of parts per million in life supporting atmospheres the effect on the partial pressure of oxygen would be negligible. But yes the oceans could be acid enough to kill everything in it.
– Ash
Commented Nov 15, 2021 at 6:16
• Globally or just locally near the equator? Commented Nov 15, 2021 at 18:48