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DENSITAS

DENSITAS. PENGANTAR OSEANOGRAFI IV. Densitas dirumuskan : Sangat penting  akan mempengaruhi sirkulasi termohaline dan gerak vertikal perairan ( vertical mixing ) Densitas tidak bisa diukur langsung  ditentukan dari data suhu , salinitas dan tekanan. Lapisan permukaan dan gradien

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DENSITAS

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  1. DENSITAS PENGANTAR OSEANOGRAFI IV

  2. Densitasdirumuskan: • Sangatpenting akanmempengaruhisirkulasitermohalinedangerakvertikalperairan (verticalmixing) • Densitastidakbisadiukurlangsung  ditentukandari data suhu, salinitasdantekanan

  3. Lapisanpermukaandangradien kecil (1,020 – 1,030 gr/cm3) • Densitasbertambahjika • Salintasmeningkat • Suhumenurun • Tekananmeningkat • Lapisandalam. ex: 0 = 1,028  5000 = 1,151 gr/cm3

  4. Lalu…. Bisakahsalinitastinggi Beradadiatas air salinitasrendah??

  5. Vertical profile

  6. Vertical) circulation driven by density  Thermohaline Circulation

  7. Kalkulasidensitas • Densitas air laut > 1000 kg/m3, tetapitidakpernah > 1100 kg/m3 (perubahanbersifatpuluhan kg/m3) • Untukkemudahkanpenulisan, densitasdinyatakandengan sigma () Densitas (sigma) Insitu (S,t,p) S,t,p = (S,t,p –1) x 103 Contoh : S,t,p= 1,02754 S,t,p= (1,02754 – 1) x 103 = 27,54

  8. sigma-nol (o) • o = (s,0,0 - 1) x 103 • o Hanyadidapatdarinilaisalintasmelalui Sigma t (t) • t = (s,t,0 – 1) x 103 • Hubungan tdano adalah : t = o –D Dimana: D  faktorkoreksi(diberikandalamTables of Seawater Density ) • o = 0,069 + 1,4708 S –0,001570 S2 + 0,0000348 S3

  9. Untukmenghitung , FofonofdanTabata (1958) membuatpersamaan • Dimana T adalahsuhu A0 = 67,26 A10 = 1,0 A20 = 0 A1 = 4,53168 A11 = - 4,7867 E-3 A21 = 1,8030 E-5 A2 = -0,5459 A12 = 9,8185 E-5 A22 = - 8,164 E-7 A3 = -1,9825E-3 A13 = -1,0843 E-6 A23 = 1,667 E-8 A4 = - 1,438E-7

  10. Ekman (1908) menghitungpengaruhtek (p) padaberbagai t dan s s,t,p, sehinggat dapatdikoreksis,t,p ( densitasinsitu). • Bjerkness and Sandstron (1910) membuattabel: t,s,psampai 10.000db. • Hesselberg and Svendrupmenyederhanakantabel t,s,plebihmudahdihitungdarit

  11. Water Masses Oceanic Surface Current

  12. The Approximate boundaries of the main upper water masses in the ocean

  13. T-S Diagrams t • Karenaadanyaperbedaan T-S padasetiapmassamassaperairan identifikasimassaair

  14. Depth (pressure), Salinity and Temperature • Tekananditentukandaripershidrostatik P = -gz P = gr/cm3.cm/det2.cm = gr cm/det2.1/cm2 = dyne/cm2 = 1/105dbar • 1 dbar = 1/10 bar = 105dyne/cm2 CONSOL • Berapatekanan air padakedalaman 1 m??

  15. P = -gz  = 1,035 gr/cm3 g = 980 cm/det2 z = -100 cm P = - (1,035 gr/cm3 ) x 980 cm/det2 x (-100 cm) = 101430 gr cm/cm2 det2 = 101430 dyne/cm2. = 1,01430 dbar 1 dbar • 1000 meter tekanan air  1000 dbar.

  16. Effect of Pressure

  17. Mixing Processes in The Ocean Laminar Flow Turbulent Flow

  18. Horizontal mixing >> vertical mixing Density < Density > Density > Density < More stable more energy

  19. Water base on stability Warm/ Less Salty Cool/ Salty Warm/ Salty Cool/ Less Salty Cool/ Salty Warm/ Less Salty Cool/ Less Salty Warm/ Salty Instable Difusion Convection Instable Salt Finger Always Stable Always Instable E = 0  Neutral E < 0  Instable E > 0  Stable

  20. Salt Finger Process Effect only a few cm

  21. Internal Wave

  22. Effect of internal wave

  23. Front

  24. Eddies

  25. TAMAT UNTUK EPISODE KALI INI

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