The Oceans, Solid Earth, the Carbon Cycle, and Climate\\ PART II The Oceans, Solid Earth, the Carbon Cycle, and Climate\\ Chapter 5, pages 91

“Wind-drift” currents – friction (wind stress) drags ocean surface in general direction of winds Fig 5.1

This surface circulation affects the top 50-100 meters of ocean Continents then deflect the currents, leading to gyres Fig 5.2

Ekman Spiral – The coriolis effect turns the surface flow in a direction that is about 20-45o from the wind direction, with a net (average) movement of water that is 90o from the direction of the wind (to the right in the northern hemisphere). Fig 5.3

This Ekman transport (pulling of the upper ~100 meters of water to the right of the surface winds) results in the convergence of water at the center of the wind-drive gyre, so that a ‘bulge’ in sea level occurs. Fig 5.3

Surface layer ‘thickening’ (or bulge) leads to vertical (downward) motion because of differences in weight of water columns. (The opposite occurs in regions where the surface layer thins – and this is responsible for upwelling. Fig 5.4

Fig 5.5 Geostrophy – flow that is determined by the balance of the pressure force (from the center of the gyre) and the Coriolis effect, so that the flow of the top 100 m of the ocean is at right angles to the direction of the pressure force, or clockwise in the northern hemisphere.

Short Question 14 Due the oceanic gyres, the climate in the North Atlantic is much colder and more variable than it would be without oceanic currents much warmer and less variable that it would be without oceanic currents no different from what it would be without oceanic currents

The composition of seawater Table 5.1

Short Question 15 Which of the following is the most abundant ion in seawater? calcium (Ca+) sodium (Na+) magnesium (Mg2+) potassium (K+) strontium (Sr2+)

The composition of seawater Table 5.1

Take home “problem” – for next time Convert the mass ratios in Table 5-1 into number ratios, and show that the ions are balanced (positive charge equals negative charge)

The composition of seawater Cl = 35.5 g mole-1 Na = 23.0 SO4 = 96.0 Mg = 24.3 Ca = 40.1 K = 39.1 HCO3 = 61.0 Br = 79.9 0.535 mol kg-1 0.459 0.055 0.053 0.020 0.010 0.0003 0.0008 Table 5.1

Why don’t the ions balance? http://www.seafriends.org.nz/oceano/seawater.htm

Short Question 17 Do the positive and negative ions in Table 5.1 balance? Yes (b) No (c) didn’t do the calculation

The vertical structure of the ocean pycno = “dense” thermo = “heat” halo = “salt” Fig 5.6

Cross section (latitude and depth) of temperature Atlantic Pacific Fig 5.7

Cross section of salinity Fig 5.8

Formation of cold, saline water Fig 5.8

Formation of cold, saline water Fig 5.8

Short Question 16 The coldest, densest water in the ocean is formed (a) along the sea-ice margins near the poles (b) at the geographic north pole (c) at the geographic south pole (d) both (b) and (c) (e) at the center of the Atlantic ocean

Fig 5.14

Fig 5.12

Fig 5.15

Short Question 18 __________are responsible for the direction of the gyres of the earth's major oceans. The tilt of the earth's axis of rotation and the elongation of its orbit Wind-driven transport and the coriolis force (c) Tides and deep convection (d) Variations of density and western intensification (e) Subduction and continental drift

Short Question 19 The thermohaline circulation refers to coastal upwelling and downwelling driven by Ekman transport. vertical motions in the ocean resulting from changes in temperature and salinity. the manner by which the polarity of water helps dissolve ions. the uptake of carbon dioxide by the surface layers of the ocean. the intensification of currents on the western boundaries of the oceans.

Assignment 5 Each student must turn in a separate 2-3 page that lists the other members of the group. Working in teams of 3-4 (all classmates from this section), listen to the NPR story and read the “Perspective” piece on the Denver Post and discuss some of the outstanding questions related to understanding the role of ocean circulation in earth’s climate and potential changes due to human activities. Start with the hypothesis “Greenland’s Ice Sheet is melting more rapidly due to human activities”. (1) Discuss potential mechanisms for why warming in Greenland may be occurring faster than other parts of the globe. (2) Using credible sources (i.e. NOT blogs or opinion pieces), discuss what uncertainties face scientists who are trying to determine the causes of the increased glacial melting. (3) What information do you think will be needed in order to determine whether or not mankind’s activities are responsible for this change?