Ocean Temperatures. Atlantic Temp Section. Seasonal (Shallow) Thermocline. Better Atlantic Temp Section

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1 I. Fundamental Principles Physical Properties Conservation of Heat Why Does the Ocean Circulate? Waves & Tides Ocean Temperatures II. Ocean Circulation Conservation of Mass Forces & Balance of Forces Effects of Earth s Rotation Wind Driven Circulation III. The Role of the Ocean in Climate Thermohaline Circulation ENSO The Poles Hurricanes Profile for Tropics & Subtropics Polar regions have uniform temperature vs. depth Atlantic Temp Section Better Atlantic Temp Section Seasonal (Shallow) Thermocline 1

2 Temperature Profiles Potential Temperature (θ) The temperature a water parcel would have at the surface, if it were raised to the surface adiabatically. Adiabatic Process - no heat is gained or lost 1st Law of Thermodynamics Δ E = Δ Heat + Δ Work For an adiabatic process:»δ E = Δ Work Bring Water Parcel Down (sinking) Work done on Parcel: Δ Work Δ E Δ Temp Potential Temperature Why Potential Temperature? θ removes the effect of pressure on temperature Salinity Surface T= 1.0 C θ=1.0 C Total amount of dissolved material in seawater T= 1.1 C θ=1.0 C 35 psu = 35 ppt = 35 o/oo = 35 grams of dissolved material in 1 kg of water Deep T= 1.2 C θ=1.0 C If S = 35, what % of the sample is dissolved material? 2

3 Major Constituents 86% Na and Cl 99% top 6 All elements not in this table are Trace Elements Ratios of major ions do not change RULE OF CONSTANT PROPORTIONS Principal of Constant Proportions Composition of salinity (dissolved material) is the same from place to place Means that the relative amount (%, ) of each major ion is the same whether salinity is 15 or 30 If you know the concentration of one ion, you know the concentration of all the ions, and you know the total salinity S (o/oo) = x CL(o/oo) CL = chloride concentration or chlorinity Ocean Salinities A 1 kg sample of seawater contains gm of chloride. How many grams of calcium are in the sample? Salinity Profile Global Surface Salinity Halocline 3

4 Controls on Global Salinity Surface salinity determined by surface Freshwater Flux E - P (cm/y) N/S Cool and rainy N/S Desert belts 5-10 N/S Warm and rainy tropics ρ = mass/volume Density (ρ) Units kg/m 3 or gm/cm 3 Ocean Density between kg/m 3 50% of ocean between kg/m 3 Average density ρ = 1027 kg/m 3 Density is not measured Density is a function of T, S, P Equation of State kg o #= ! a(t $ 10 C) + b(s $ 35 psu) + kp" m % & a is negative Can use decibars or meters: 1 db = 1 m Density (σ) Easier way of labeling density σ = (ρ ) when ρ in kg/m 3 σ = (ρ - 1) x 10 3 when ρ in gm/cm 3 Average density σ = 27 Theoretically σ has units of kg/m 3, but DO NOT use σ in formulas, problems, etc. Effects on Density How ρ changes when T changes depends on the initial properties of the water. Effect of T, S on ρ 4

5 T - S - σ Diagram Cabbeling Effects of Pressure on ρ 1) ρ = Mass/Vol Volume decreased 2) Pressure changes the temperature. Temperature affects the density. One of these effects is HUGE! Types of Density If ρ in units of kg/m 3 : In-situ σ = (ρ s,t,p 1000) Never used for deep water Sigma t σ t = (ρ s,t,0 1000) Is density parcel would have if raised to the surface Removes Pressure s HUGE effect on compressibility Potential σ θ = (ρ s,θ,0 1000) Is density parcel would have if raised to the surface adiabatically Removes Pressure s HUGE effect on compressibility Removes Pressure s much smaller effect on temperature Atlantic Potential Density Surface densities vs. latitude exact opposite of temperature also Isopycnal Pycnocline 5

6 Atlantic Potential Density Very Stable E = - 1 d σ t ρ dz z - depth ρ - 27 Q: Calculate the stability between 50m and 150m. Stability Equation 0 m m m m - σ t = 27.5 σ t = 28 E = - 1 d σ t ρ dz Stable: E is +, larger the number, more stable the water is Neutrally Stable: E=0 Instable: E is -, short lived Much WORK to move 1 km vertically No WORK to move 10,000 s km horizontally 6

7 Summary Temperature Range Profiles Surface Dist. Types Density Units, ρ and σ Equ. of State Types Profiles Surface Dist. Surface Distributions Salinity Units Profiles Surface Dist. Stablity Definition Role of ρ Calculation Importance Very close together 7