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Weekly result

This weekly report analyzes the heat and mass balance in the Gulf of Mexico over a 5-year period, considering the effects of wind on circulation and heat transport. The study examines the impact of wind on eddy tracks, the distribution of heat in the Gulf, and the influence of downfront wind. The report also explores the mass balance and proposes a hypothesis regarding the circulation changes caused by local wind patterns.

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Weekly result

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  1. Weekly result Eda 20100122 Heat and mass balance in GOM 5years runs with and without wind from the same IC.

  2. wind nowind Heat transport Z=0m Z=-100m Z=-300m

  3. Today’s topic • The 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)

  4. OHC wind nowind Smooth (7points) vertical velocity at z=-100m • Eddy dumps the heat, the near coast downwelling also result in higher OHC. wind nowind

  5. 90w 5years mean T U PV downfront upfront downfront upfront Wind Nowind Wind-nowind

  6. 90w mean, with eddy pass by T U PV downfront upfront Wind Nowind Wind-nowind

  7. Summary for upper 2 pages • The 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.

  8. Along 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?

  9. Along isobath 5yrs mean T W PV Wind Nowind Wind-nowind

  10. Summary for upper 2 pages • West 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.

  11. Find eddy propagates direction and speed nowind wind EL=0.3m EL=0.2m Define mean track

  12. Zoom in one event (time is close to each other) to calculate eddy propagate speed Along track EL wind nowind Speed (to the west): Wind: 334km/53days=7.3cm/s Nowind: 211km/28days=8.7cm/s Note: wind and nowind are based on different tracks in order to catch the eddies.

  13. Summary for upper 2 pages • Wind: • 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 of the nonlinear self advection (Smith and O’brien,1983). • Eddy westward propagate speed is slower than nowind case because of the eastward background flow. Note: big eddy supposes to propagate faster because c=-βRd2

  14. Mass balance Wind 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. Qf Qeddy q Qy Q

  15. Mass balance EG Control Volume Nowind Wind Qeddy Qeddy Qf Qf q q Q=30.58Sv Qy=+6.91Sv For Gulf Control Vol: Q-Qy=q+Qf=23.67Sv Q=33.19Sv Qy=+9.23Sv For Gulf Control Vol: Q-Qy=q+Qf=23.96Sv Qy Qy Q Q 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 )

  16. Qeddy • Qeddy is eddy’s transport=∫∫udydz • depth is about the same in wind and no wind~800m • y length comes from eddy’s size, and we have u already(p12) √area~y length Wind:210km Nowind:175km Qeddy_wind=210km*800m*7.3cm/s=12.26Sv Qeddy_nowind=175km*800m*8.7cm/s=12.18Sv Eddy size: find the el>0.1m (exclude LC and shelf region), area=sum(dx*dy)

  17. Summary for mass balance • 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+3.03 Nowind: 12.18=6.91+5.27 The hypothesis is valid.

  18. N Wind 800m to bottom stream function Volume transport Heat flux

  19. N Wind Surface to 800m stream function Volume transport Heat flux

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