Chapter 6: Ocean Chemistry Reading: Chapter 6

1. Chapter 6: Ocean Chemistry Reading: Chapter 6 ftp://ucsbuxa.ucsb.edu/opl/tommy/Geog3awinter2011/

2. Class Objectives Gain knowledge of scientific methods and theories. Increase understanding and appreciation of ocean and atmosphere. Appreciate historical perspectives of science and its evolution. Learn of similarities and differences of ocean and atmosphere. Obtain skills in reading maps and interpreting data presentations. Develop ability to read and objectively evaluate science articles.

3. Chemistry Science of matter – its composition, structure, properties, and behavior.Chemical OceanographyInvolves physics, biology, and geology of the world ocean. Interdisciplinary.

4. Figure 6-4 Classification of matter. Matter is solid material with mass (physics: mass and energy) Mixtures = different types of matter separable by physical means Substances = elements and compounds Elements = atoms (neutrons, protons, electrons) e.g., H, O, Na Compounds = atoms chemically united (like H20 and NaCl) Molecules = two or more atoms united (i.e., H20) where H is hydrogen atom; O is oxygen atom (inorganic & organic) Chem. Physics Physics

5. Motivation Chemistry affects life in ocean and vice versa (i.e., biochemistry)Chemistry is important for climate. Physical properties affected by chemistry (i.e., salinity).Atmosphere is affected by ocean chemistry and vice versa.Pollution is often chemical issue.

6. British ship HMS Challenger: 1872-1876First oceanography expedition – refit warship200 feet long, 2300 tons, engine and sail

7. Route of the HMS Challenger713 days at sea, out of port 1,606 days 69,000 nt miles or about 79,000 statute milesWent near Antarctica

8. Challenger Facts • C. Wyville Thomson led expedition • John Murray led analyses • Capt. George Nares and 200 crew onboard • Took place just after U.S. Civil War and • during early polar exploration through early 1900’s. • 492 soundings with depth using lead lines • (144 miles of sounding rope and 12.5 miles of piano wire) • 263 water (hydrographic) stations; 133 bottom dredges • 151 open water trawls for organisms (4,700 new species) • Measured currents • Did excellent chemical analyses (i.e., relevant to carbon, etc.) • Discovered Mid-Atlantic Ridge and Mariana’s Trench • Found life in deep sea (disproved azoic (dead) zone) • No primordial slime on seafloor (postulated by Ernest Haeckel) • Data stored in UK; 50 volumes of reports still used.

9. Challenger Expedition Samplers Instrument and sampling platform Shallow-water dredge

10. Challenger Expedition Samplers and Labs Buchanan water sampler Natural history laboratory Carbonic acid analysis apparatus Chemistry laboratory

11. British ship HMS Challenger: 1872-1876Why so important?

12. HMS Challenger: 1872-1876Provided data concerning composition and structure of ocean. Data are still useful. Why??? An original box of photographic negatives from Challenger expedition.

13. HMS Challenger’s contribution:“the greatest advance in the knowledge of our planet since the celebrated discoveries of the 15th and 16th centuries.” John Murray in 1895

14. Review: HMS Challenger’s contribution:“the greatest advance in the knowledge of our planet since the celebrated discoveries of the 15th and 16th centuries.” John Murray in 1895 What were some of the advances??

15. What is in Seawater?

16. What is in Seawater?Seawater is composed of H20 and many dissolved elements and compounds.

17. Fig. 6-5 Periodic Table of Elements – Major seawater elements (purple) and biologically important elements (in red; i.e., nutrients) are highlighted. Are all of these elements in the ocean? Your favorite nut mix?????

18. Geometry of a water (H20) molecule. O has 8 protons, 8 neutrons, 8 electrons. H has 1 proton, 1 electron Covalent bonding – Sharing electrons between H and O atoms Note polarity of the H2O molecule

19. Important Properties of Water Molecules Water has high surface tension (hard to pull molecules apart). Capillary waves: restoring force depends on polar property of H20 molecules and H-bonding. H2O is very good at dissolving materials. Water exists as solid, liquid, and gas.

20. Water is an excellent solvent. Element like Na with 11 electrons readily donates its ‘extra’ outer shell electron while those like Cl with 17 electrons (‘missing’ an outer shell electron) readily accepts an electron. Outer shell of electrons wants to be stable (i.e., 2 electrons in 1st, 8 electrons in 2nd and 3rd shells, etc.; Periodic Table) So, Na+ ion and Cl- ion together make a stable molecule. When together, they form NaCl via ionic bonding.

21. Figure 6-10 Salt as a solute. Higher temps allow for more solute to be dissolved.

22. Where do dissolved and particulate materials in ocean come from? Hint: Chemistry of ocean involves interactions of land, ocean, and atmosphere and biological organisms. p. 90

23. How does material enter oceans? • Volcanoes, hot springs, vents (i.e., chloride, Cl) • Weathering rock (i.e., sodium chloride, NaCl) • Rivers • Rain and atmospheric deposition • Biological processes (recycling really) • Meteors from space

24. Fig. 6-1 What chemicals are in ocean waters? An internet ad: Fine grain sea salt is obtained by the evaporation of seawater. It is the perfect substitute for plain table salt. Packed with minerals, this fine grain sea salt is known for its better taste and texture than table salt. Nutrition? See Salt Guru #1 on YouTube.

25. The percentage of all foods and beverages with sea salt jumped from 5% in 2006 to more than 8% in 2010. Is there a sea salt standard for food?

26. Constituents of ocean salinity. Note: NaCl makes up 86% of dissolved elements. Example 1kg of Seawater Contains:

27. Fig. 6-11 Relative proportions of major constituents of dissolved elements in seawater. Dittmar’s Principle. Based on HMS Challenger data. Works for open ocean.

28. Open Ocean – Dittmar’s Principle applies. * *Avogadro’s number is number of C atoms in 12 gm of Carbon. Avogadro’s number is 6.023 X1023 atoms/mol. A mole (mol) is the amount of substance of a system which contains as many elementary entities as there are atoms in 0.012 kilogram (or 12 grams ) of carbon-12.

29. Approximate Composition of Open Ocean Seawater • Seawater by weight percent: Water 96.5% or 965 ppt Dissolved material 3.5% or 35 ppt Total 100.0% or 1000 ppt ppt = parts per thousand, like percent (%) but using 1000 for reference base instead of 100. Aside: 1) What percent by weight is water in the human body? 2) What percent of human body is Na? Cl?

30. Chapter 6: Ocean Chemistry Reading: Chapter 6 Ocean Field Trips in Southern California: See folder on ftp site: ‘Field_Trips_W11’ ftp://ucsbuxa.ucsb.edu/opl/tommy/Geog3awinter2011/

31. Approximate Composition of Open Ocean Seawater • Seawater by weight percent: Water 96.5% or 965 ppt Dissolved material 3.5% or 35 ppt Total 100.0% or 1000 ppt ppt = parts per thousand, like percent (%) but using 1000 for reference base instead of 100. Aside: 1) What percent by weight is water in the human body? 50-60%, ppt? 2) What percent of human body is Na? Cl? 0.15%, 0.15%, ppt?

32. What is formal definition of Salinity?

33. Definition of Salinity • Number of grams of dissolved material in 1 kilogram of seawater • Units in parts per thousand (ppt) or practical salinity units (psu)

34. Salinity Determination • Given 70 gm of dissolved material in 2 kg or 2000 gm of seawater, what is the salinity? • S = 70 gm/2000gm • = 35 gm/1000gm = 35 gm/1000gm • = 35 ppt or psu

35. Fig. 6-2 Concept of ocean water column. Properties usually vary with depth. We want to know how many of each molecule type is in the ocean per unit volume and how the concentrations vary with depth.

36. Dittmar’s Principle • In open ocean, total amount of dissolved materials may change, but ratios of the elements remain very nearly the same (Table 6.1 applies in open ocean) • Thus, we can calculate salinity from chlorinity using formula • S = 1.8 X Cl

37. Example Calculation • Given Cl = 20 ppt, what is salinity? • S = 1.8 X Cl • = 1.8 X 20 ppt = 36 ppt • Where does this method fail? Rivers, estuaries, bays, near coasts

38. Measurements of salinity using conductivity • Devices for measurements: CTD: conductivity, temp., depth Salinometer Satellite sensors being developed using microwave energy CTD

39. Salinity affects water conductivity.

40. Measuring salinity using a CTD. Also collecting water samples. Fig. 6-12 Inc. S gives inc. Cond.

41. Biologically Important Nutrients for Supporting Phytoplankton (Algae) Phytoplankton (drifting algae) are fundamental to life on Earth Microscopic view of phytoplankton

42. Fig. 6-13 Biologically important nutrients for phytoplankton: nitrogen, nitrate, nitrite, silicate, phosphate, ammonia, iron. Phytoplankton

43. SeaWiFS This map of global chlorophyll (green in color) concentrations (proxy for phytoplankton = microscopic drifting plants) illustrates quite clearly the eutrophic (high in macronutrients) regions of the world ocean, seen in red and green, and the oligotrophic (low in macronutrients) regions, seen in blue and purple. Which area are oligotrophic? Eutrophic?

44. Fig. 6-14 Colored dissolved material is brownish material in stream entering the Pacific. Why important?

45. Dittmar’s Principle does not work for rivers, bays, estuaries, and nearshore ocean waters.

46. Fig. 6-15 Oxygen minimum zones. Why important?

47. Global Carbon Cycle: Carbon Reservoirs Exchange Rates Residence Times (See video Inconvenient Truth on reserve in Davidson Library) Receding Glacier 1941 2006

48. Fig. 6-19 Exchange of organic Carbon among various reservoirs. Note sources and sinks of organic Carbon. 2Gtons/yr extra!!! Exchange Rates in Gtons C/yr (Gtons C stored in each reservoir) Note: Gtons = 109 tons

49. Fig. 6-20 Reservoirs, (residence times) and exchange rates [in Gt/yr with arrows] of all Carbon stored on Earth. Which is smallest reservoir? Note: About 2 Gt of CO2 are accumulating in atmosphere per year now.

50. Keeling curve showing increase of atmospheric CO2 at Mauna Loa Observatory – most important curve in science today. Values reached 1500ppm when dinosaurs lived. Some models predict that by end of this century values may reach 560 ppm.