Weekly resultWeekly resultEda20100122

Heat and mass balance in GOM5years runs with and without wind from the same IC.

Heat Heat transporttransport

Z=0m

Z=-100m

Z=-300m

wind nowind

Today’s topicToday’s topicThe wind case shows different circulation

and heat transport. Circulation affect eddy’s track and speed?

(p11-p13)The higher heat in western Gulf may come

from shelf and eddy.South of the eddy has higher heat, this may

relate to downfront wind effect. (p5-p10)If the eddies dump heat in the western gulf

result in higher OHC. (p4)Mass balance concludes from a simple

assumption. (p14-17)

Eddy dumps the heat, the near coast downwelling also result in higher OHC.

wind nowind

Smooth (7points) vertical velocity at z=-Smooth (7points) vertical velocity at z=-100m100m

OHC wind nowind

90w 5years mean90w 5years mean

T U PV

Wind

Nowind

Wind-nowind

downfront upfront downfront upfront

90w mean, with eddy pass 90w mean, with eddy pass byby

T U PV

Wind

Nowind

Wind-nowind

downfront upfront

Summary for upper 2 Summary for upper 2 pagespagesThe deeper isotherm is contributed from the

wind. The asymmetries in isotherms & PV’s about

the eddy-center @26N are due to downfront to the south and upfront to the north.

The downfront effect induces the instability and mixing, resulting in the deeper isotherm and near positive PV.

The higher heat energy has been transferred to the western Gulf.

Downwelling at the northern shelf is due to the upfront wind, the warmer water is also carried to the west.

Along 3500m isobathAlong 3500m isobath

Find the grids between 3300~3500m

High energy had been transferred in wind case

South of the eddy has higher heat transport

downfront effect?

Along isobath 5yrs meanAlong isobath 5yrs mean

T W PV

Wind

Nowind

Wind-nowind

Summary for upper 2 Summary for upper 2 pagespagesWest of the section represents the

situation when the eddy settles down, east of the section is the passage of the eddy.

In wind case, downward motion is strong in the near surface layer deepens the isotherm. The PV is smaller (close to positive). This is similar as 90W may contributed from downfront wind.

Find eddy propagates direction and Find eddy propagates direction and speedspeed

EL=0.2m EL=0.3m

wind nowind

Define mean track

Along track ELAlong track ELEnlarge one event (time is close to each other) to calculate eddy propagate speed

nowind

wind

Speed (to the west):Wind: 334km/53days=7.3cm/sNowind: 211km/28days=8.7cm/s Note: wind and nowind are based on different

tracks in order to catch the eddies.

Summary for upper 2 Summary for upper 2 pagespagesWind: The large EL can propagate further

westward. (see EL=0.3m) It means the eddy is larger or it dissipates slower.

Eddy tends to move more southward than nowind, because there is a eastward flow south of northern basin. (see p.3 up-left figure)

Eddy westward propagate speed is slower than nowind case.

Mass balanceMass balance The Gulf is closed, so the mass has to go

somewhere after eddy shedding, either goes out from Florida strait or Yucatan channel.

Hypothesis: The local wind changes the circulation,

showing the strong westward flow in the shelf, so the Florida return flow may weaken; as a result, the Yucatan outflow is strengthened.

Q

q

Qy

Q

fQeddy

Wind

Mass balanceMass balance

Q

q

Qy

Qf

Qeddy

Nowind

Q

q

Qy

Qf

Qeddy

Wind

Q=30.58SvQy=+6.91SvFor Gulf Control Vol:Q-Qy=q+Qf=23.67Sv

Q=33.19SvQy=+9.23SvFor Gulf Control Vol:Q-Qy=q+Qf=23.96Sv

For EG Control Vol:Q-q=Qeddy=Qy+Qf is about the same in wind and no wind!(Eddy in wind is larger but moves slower and in nowind is smaller but moves faster )

EG Control Volume

QQeddyeddy

Qeddy is eddy’s transport=∫∫udydzdepth is about the same in wind and

no wind~800m y length comes from eddy’s size, and

we have u already(p12)

Eddy size: find the el>0.1m (exclude LC and shelf region), area=sum(dx*dy)

√area~y lengthWind:210kmNowind:175km

Qeddy_wind=210km*800m*7.3cm/s=12.26SvQeddy_nowind=175km*800m*8.7cm/s=12.18Sv

Since Qeddy is about the same, and Qy is larger, so Qf is smaller in wind case.

Qeddy= Qy + Qf

Wind: 12.26=9.23+3.03Nowind: 12.18=6.91+5.27

The hypothesis is valid.

Summary for mass Summary for mass balancebalance