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[Music]

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[Applause]

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thanks for including me in succession a

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machine zone from Peking University and

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my advisor is dream Yong

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today's topic is wind driven ocean

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circulation on tidally locked aqua

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planets and I want to sorry I want to

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focus on two main features of the

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associate circulation on these kind of

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planets oceans rotation and the

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equatorial vertical motion first let me

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introduce the research background of our

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experiments when we search for life

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beyond the solar system we mainly focus

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on the planets in the habitable zone

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around M dwarfs because we have bounced

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several subscribe planet system like the

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Trappist one system and because the

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habitable zone around M dwarfs are very

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close to a star so the planets will

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easily get tidally locked due to the

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strong tidal force as a result the one

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side of the planet will permanently face

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the star and the other side will get no

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radiation hitting at all so as a result

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the climate on the planets were likely

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to be an IPO mode because so the open

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ocean area will become straight to a

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constricted in the day's side around the

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substellar point however if we can take

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ocean heat transport into consideration

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the open ocean area will be largely

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expanded because ocean can transport

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heat from the substrate point to higher

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latitudes and to the next side and we

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call it lobster mode because it is like

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a lobster with two claws here and a long

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tail to the night side and this is very

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significant for the habit ility orders

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of planet because with ocean heat

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transport it can warm the night side and

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thus it can protect the atmosphere from

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condensing down on the next side and it

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can also restrict the thickness of the

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ice from thousands of Kip meters if we

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don't care take ocean heat transport as

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Ken gross as that seek to the order of

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tens of meters

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so that's the water will not freeze at

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the Nightside so that will be the liquid

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water will be trapped on the night side

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to Isis a formal researchers has found

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this phenomena and our work is many to

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show to the inner mechanism of the

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circulation and give a clearer picture

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of it so carried out our experiments

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earth-like aqua planets with ocean

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depths of around a thousand kilometers

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the model will use the deceased sm-3

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acaba coupling model with active ocean

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band and sea ice dynamics because while

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simulating aqua planets tidally locked

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around ma off so we did some change in

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the spectrum and the rotation period and

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next to this is the main patch of our

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speech the most important feature of

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untidily locked aqua planets is the

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ocean soup rotation this animation shows

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the ocean surface zonal velocity we can

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see that at low latitudes the ocean

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current is uniformly eastward and it can

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reach the about one meter per second we

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know that is quite large this week the

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oceans of rotation not only just exist

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at the surface of the ocean in fact it

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can reach until the bottom of the ocean

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in our experiment so we want to figure

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out what makes this kind of super

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rotation because the ocean current is

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mainly wind driven so we want to have a

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look at the wind stress the wind assess

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is shown here it is convergence to the

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sub zero point as well as two hot spots

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due to the ocean heat transport and we

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also noticed that the wind stress on the

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west side is stronger than the east side

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so if we will calculate the zonal mean

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results we'll find that

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wind stress the redline is also used in

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stored at low latitudes so we may get

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the conclusion that the oceans of

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rotation is Menem driven by the

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atmosphere super rotation however our

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story is not that simple because we can

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see there are some differences between

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the atmosphere and the ocean in

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atmosphere we are two Jets while in the

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ocean leaves only one jet so there must

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be some inner adjustment within the

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ocean in order to answer this question

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we did a more careful analysis on the

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momentum budget using the zonal mean

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time average donor momentum equation and

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we divided the advection terms into mean

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circulation stationary Eddy and the

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transient at the moment transport as a

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result we can find although the wind

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stress is not very strong at the equator

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the stationary L is the Purple Line is

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very strong at the recruiter and it can

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compensate for the wind stress and we

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can see that as some of them reaches the

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maximum and the equator so the

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stationary Eddy transport is very

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important because it changes from the

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atmosphere to Jets into the only one jet

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at equator of the ocean and this is all

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about the surface oceans of rotation and

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let's move to the next part of the

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equatorial vertical velocity we know

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that the vertical velocity is also very

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important to the biology because when

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there is upwelling area there will be a

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mixing of the ocean and the nutrients

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will be transported from the bottom of

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the ocean to to upper levels and we

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focus on the equatorial area because the

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most significant features is in in the

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earthly creature and the most important

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feature is that there is a downwind area

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to the east side and an upwelling area

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on the east side and this can be

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completely explained by the Ekman

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transport because we know that the other

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wind stress is convergent through the

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subsolar point so the Ekman transport

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near the equator will be like this way

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so it will converge on the west side and

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the diverge on the east side and this

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convergence and divergence will cause

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the tongue wielding area and the upper

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waiting area however we also find that

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the momentum transport is very important

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to the downwind area we know that the

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down wording is caused by the

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convergence of the water and we can

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divide the convergence into X direction

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and y direction the ecumene transport is

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meaning is meaning contributed to the y

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direction but we have find that the X

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directions convergence the blue line has

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a large contribution to the down

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wheeling so what the cause is this kind

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of his own incursions we found that it

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is the Eddy momentum transport this

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figure shows the momentum transport from

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higher latitudes to a liquid and it

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reaches the maximum at around a hundred

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degree East so this kind of momentum

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transport will cause also the donor

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velocity to reach maximum here and

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because the donor velocity is maximum

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here and so it will cause the

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convergence east of it and thus

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contributed to the down wielding area

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now we have a basic picture of the ocean

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circulation and hydrological planets

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first we can observe that there exists

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with a atmosphere protection as well as

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options predation and we have some

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differences with 2js in the atmosphere

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and one jet in the ocean this can be

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explained by the eddy momentum transport

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which is dominated by the stationary

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eddies

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and we have this kind of wind stress and

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the momentum transport and we will get

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the vertical motion of the ocean near

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repeater to be a done wheeling area on

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the east side and upward in area on the

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west east side and this not only occurs

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at this experiment it actually occurs in

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different conditions experiments for the

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tidally locked aqua planets so it's more

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widely applied and that's all for my

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presentation and some other things is

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that we can we notice that the

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equatorial super rotation is not strong

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as a surface but at the deeper in the

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ocean and this is caused by the thermal

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wind relationship and it is the same as

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what we know the equatorial undercurrent

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that occurs on earth specific and that's

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all thank you yeah Charlie lineweaver

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from the Australian National University

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I got the impression that you were

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modeling tightly locked rocky planets in

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the habitable zones of M dwarfs is that

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right

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yes but actually we is rocky planets

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with oceans of around a thousand metres

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and we have no lens distribution of this

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planet all right and does the things

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that your results do they depend very

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strongly on how close this thing is to

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the to the post on for example is inside

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of the habitable zone the outside of

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habitable zone yet it's a wide it's semi

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wide okay and this is the planets that's

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in the middle edge middle range of the

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habitable zone and you think it would

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change depending on if you a little

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closer a little further out yes and

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another paper from my advisor Drina

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in this about a baby February 2019

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points out that if we push the planets

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to the inner edge of the habitable zone

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then the wind then the temperature

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gradients will be weaker so the wind

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stress will also be weaker and the ocean

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current will be weaker I mean in the

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inner edge of the habitable zone the

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ocean heat transport we are not so will

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be not be so important and the

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atmosphere oceans oops ocean transport

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we hope atmospheres heat transport will

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be more important and on the outer edge

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is the reverse and the outer edge we

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haven't done much about the research

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thank you

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I think hey nice talk techno music

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University of Chicago so you showed that

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the horizontal at a momentum transport

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leads a super rotation but as the

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vertical momentum transport also

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reinforce super rotation actually with

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this result is than vertical integrated

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and average because we want to wipe out

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these two terms and actually if we just

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calculate the risk based momentum budget

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in difference layers the vertical

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momentum transport is has a large

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influence but it can but it we know that

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it when it is including intergrated

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vertically it is we all just to be zero

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so we think that the oceans of rotation

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can reach the hope the whole depths of

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the ocean so we focus on the horizontal