Department of Earth and Planetary Sciences EPSC-542 Chemical Oceanography Tuesday and Thursday: 11:35AM-12:55PM FDA-348 Alfonso Mucci [email protected] Frank Dawson Adams (FDA) - 201 Teaching Assistant
Pascle Daoust ([email protected]) FDA-349 2/66 EPSC-542 Chemical Oceanography
Course outline
Week Subject 1 Introduction -organization (course description and schedule), books, evaluation scheme.
2 History of chemical oceanography The ocean as a stratified body of water Origin and evolution of the early ocean
2/3 Seawater composition -Definition of salinity/chlorinity and concept of constant relative proportions -Determination of salinity -Salinity distribution in the ocean -Validity of the law of constant relative proportions
3 Properties of water -Isotopic composition -Anomalous physical properties of water -The structure of liquid water -Influence of solutes on the structure of water
4 The behaviour of electrolytes and non-electrolytes in solution -Electrostriction -Speciation and ion-pairing
4/5 Minor elements -Concept of residence time -Distribution of minor elements in the ocean 3/66 Course outline (continued)
6 Micronutrient elements -Phosphate and the phosphorus cycle -Nitrogen and the nitrogen cycle -The ocean's internal cycle -The horizontal segregation of elements in the deep-sea
7/8 Dissolved gases -Solubility of gases in seawater -The rate of gas exchange between the atmosphere and ocean -Disequilibrium between the atmosphere and ocean -Dissolved oxygen distribution in the ocean
9/10 CO2 and the carbonate system -The chemistry of the CO2-H2O system -pH measurements in seawater -Buffer capacity of seawater -The solubility and distribution of carbonate minerals in marine sediments
11/12 Deep-sea sediments -Origin of deep-sea sediments (e.g weathering, transport, authigenic and biogenic production) -Components of deep-sea sediments (e.g. clays, carbonates, evaporites, silicates, phosphates) -Sedimentation rate -Sediment diagenesis
13 Organic matter in the marine environment -Origin and composition of DOC and POC -Humic acids and substances -The carbon cycle
4/66 Method of Evaluation: Mid-term 30% (February 27, 2020, to be confirmed) Problem sets 20% Final 50% (final examination period, in dept.)
McGill University values academic integrity. Therefore all students must understand the meaning and consequences of cheating, plagiarism and other academic offences under the Code of Student Conduct and Disciplinary Procedures (see www.mcgill.ca/integrity for more information).
L'université McGill attache une haute importance à l'honnêteté académique. Il incombe par conséquent à tous les étudiants de comprendre ce que l'on entend par tricherie, plagiat et autres infractions académiques, ainsi que les conséquences que peuvent avoir de telles actions, selon le Code de conduite de l'étudiant et des procédures disciplinaires (pour de plus amples renseignements, veuillez consulter le site www.mcgill.ca/integrity).
In accord with McGill University’s Charter of Students’ Rights, students in this course have the right to submit in English or in French any written work that is to be graded.
http://eps.mcgill.ca/~courses/c542/ 5/66 Reference books:
Bianchi T.S. (2007) Biogeochemistry of Estuaries, Oxford University Press, New York, 706 pp.
Broecker, W.M. (1974) Chemical Oceanography, Harcourt Brace Jovanovich, New York, 214pp.
Broecker, W.M. and Peng, T-H. (1982) Tracers in The Sea, Eldigio Press, Palisades, New York, 690 pp.
Chester, R. (1990) Marine Geochemistry, Unwin Hyman, London, 698pp.
Dietrich, G., Kalle, K., Krauss, W. and Siedler, G. (1980) General Oceanography, Translated from German by S. and H. Ulrich Roll, John Wiley & Sons, New York, 626pp.
Horne, R.A. (1969) Marine Chemistry, Wiley-Interscience, New York, 568 pp.
Millero, F.J. and Sohn, M.L. (1992) Chemical Oceanography, Taylor & Francis Group, CRC Press
Millero, F.J. (2013) Chemical Oceanography, 4thEdition, CRC Press, Boca Raton, 469pp
Millero, F.J. (2001) The Physical Chemistry of Natural Waters, Wiley-Interscience,
Pilson, M.E. (1998) An Introduction to the Chemistry of the Sea, Prentice Hall, N.J., 431pp.
Riley, J.P. and Chester, R. (1971) Introduction to Marine Chemistry, Academic Press, New York, 465pp.
Riley, J.P. and Skirrow, G. (1965) Chemical Oceanography, V. 1, 2, Academic Press, London
Riley, J.P. and Skirrow, G. (1975) Chemical Oceanography, V. 1, 2, 3 & 4, Academic Press, London.
Riley, J.P. and Chester, R. (1976) Chemical Oceanography, V. 5 & 6, (1978) V. 7, (1983) V. 8, Academic Press, London
Schulz H.D. and Zabel M. (2006) Marine Geochemistry, 2nd Edition, Springer, New York, 574 pp.
Stumm, W. and Morgan, J.J. (1981) Aquatic Chemistry, John Wiley & Sons, New York, 780pp.
6/66 Chemical Oceanography Frank J. Millero Fourth Edition
http://eps.mcgill.ca/~courses/c542/ 7/66 8/66 Chemical Oceanography? or
phosphate Marine Chemistry? nitrate silicate
9/66 The Earth
~12,756 km in diameter at the equator
10/66 11/66 World Oceans Map
The Blue Planet 12/66 Continents and oceans as percentages of the total world surface area
Earth = 510 million km2 Oceans = 362 million km2 or ~71% of Earth’s surface = 1.37 billion km3 = 1.37 x 1021 liters = 1.40 x 1024 g = 98% of the water on the Earth’s surface.
From: P.J. Wyllie (1976) The Way the Earth Works 13/66 Elevation map of the Earth
Darker blues are deeper water in the ocean (average depth = 3800 m) Greens are lower elevation on land (average elevation = 880 m) 14/66 15/66 Hypsographic curve of the Earth’s surface Everest = 8850 m
Continental slope Continental rise Abyssal plains Trenches
Mariana Trench = 11000 m
16/66 Distribution of land masses on Earth
Today, 65% of the continents are found in the Northern Hemisphere
From: P.J. Wyllie (1976) The Way the Earth Works 17/66 The ocean floor revealed
Continental shelf Continental slope Continental rise
25% of the continental Mid-ocean ridges crust (or 11% of the Earth’s surface) is cover ~25% of the Abyssal plain Earth’s surface presently covered by whereas mountain ranges water. cover only ~10%.
18/66 Mid-ocean ridges
Mid-ocean ridges cover ~25% of the Earth’s surface 19/66 The Ocean as a chemical system
20/66 The Ocean as a Chemical System
21/66 History of Chemical Oceanography 1627-1691 / Robert Boyle (Often considered the founder of modern chemistry and scientific oceanography, but best known for his law on the relationship between gas pressure and volume, i.e., P1V1 = P2V2 at constant T.) 1670 - “Observations and Experiments on the Saltness of the Sea”
Introduced the use of AgNO3 to test for the “saltness” of natural waters. He believed sea salts to be residues of leaching from land by rivers. Attempted to determine the total salt content of seawater by evaporation … but concluded that measurements of specific gravity provided a more accurate measure of seawater salt content.
22/66 History of Chemical Oceanography
1635-1703/ Robert Hooke (Best know for his law of elasticity, inventor of the air pump and watch balance spring)
In 1655, he became Robert Boyle’s assistant. Observed that the density of seawater in the English Channel increases with depth, which he attributed to an increase in salinity but …
23/66 History of Chemical Oceanography
1743-1794/ Antoine Lavoisier (French chemist best known for proving the law of conservation of mass and identifying the elements that make up water, i.e., oxygen and hydrogen) 1776 – First analysis of seawater following its slow evaporation (~70%), during which he observed the precipitation of calcium carbonate and calcium sulfate.
Upon further evaporation, NaCl was precipitated, followed by MgCl2 and MgSO4. He was then left with an unidentifiable residue.
24/66 History of Chemical Oceanography
1778-1850/Joseph Louis Gay-Lussac (French chemist, best known for his two laws relating the behavior of ideal gases: stoichiometry of reacting gases and the relationship between gas pressure and temperature, i.e., P1/T1 = P2/T2 at constant V).
1817 – He used titrimetry to develop simple and accurate methods to determine salt concentrations in seawater and concluded that these were constant everywhere in the open ocean, as published in “Note sur la Salure de l’Océan Atlantique.”
25/66 History of Chemical Oceanography
1778-1820/ John Murray (Scottish chemist)
Using the evaporative procedure of Lavoisier, he demonstrated that the precipitates were far from being pure salts. He proposed that seawater was made up of individual “acids and bases” and elaborated a number of gravimetric methods for the determination of individual ions.
Precipitated sulfate with BaCl2 BaSO4 Precipitated calcium as an oxalate (CaC2O4) and converted it to sulfate (CaSO4) for weighing.
1818 – Published a paper entitled “An analysis of sea-water; with observations on the analysis of salt-brines”
26/66 History of Chemical Oceanography
1770-1822/ Alexander Marcet (Physician and animal chemist)
Using Murray’s procedures, he analyzed 70 seawater samples collected in the Mediterranean and in the Atlantic . In 1819, he presented a paper to the Royal Society in which he suggested that they contained the same ingredients, bearing very nearly the same proportions to each other, and that their concentration differ only as to the total amount of their salt content.
27/66 History of Chemical Oceanography
1794-1865/ Johann Georg Forchhammer (Ph.D. Polytechnical Institute, Copenhagen)
Repeated previous studies on several hundred samples collected over a 20-year period (1843-1863) by seafaring men from different parts of the world. He analyzed for Ca, Mg, Cl, SO4 and, in some cases, K. He confirmed that the relative proportion of these ions was almost the same in all the samples. As a geologist, he was mostly interested in the fate of inorganic materials brought to the sea by rivers. He attributed their removal from seawater to the action of organisms, as skeletal components. More importantly, he concluded that the quantity of different elements in seawater is not proportional to the quantity of elements that river water delivers into the sea but is inversely proportional to the facility with which the elements in seawater are made insoluble by organisms or chemical reactions.
28/66 History of Chemical Oceanography
1872-1876 marks the period of the first serious oceanographic expedition. A chemist named J.Y. Buchanan collected seawater samples during the H.M.S. Challenger expedition. Water samples were collected at various depths down to 1500 m and stored for later analyses. On board, densities were measured with
an hydrometer and dissolved CO2 was determined by titration. Back in Glasgow, William (or Wilhem) Dittmar used a number of analytical methods to analyze the 77 water samples. He observed that the character of sea salts was the same everywhere and confirmed the previous hypothesis of the constancy of relative proportions.
Dittmar suggested that it would be possible to estimate the salinity of a seawater sample by determining one of its major constituents and, for this purpose, he suggested the use of chloride.
S = chloride content x 1.8058 J.Y. Buchanan H.M.S. Challenger 29/66 History of Chemical Oceanography
1871- 1949/ Prof. Martin Knudsen (Danish chemist)
In 1899, he published a modification of the Mohr titration method to determine chloride in solution and from this work constructed hydrographic tables which related chlorinity to both salinity and density of seawater. At the suggestion of an International Commission, a committee, composed of Knudsen, Sorensen, and others, drew up definitions for chlorinity and salinity and related each other by: S= 1.8050 Cl + 0.03
Between 1900 and 1940, most efforts were directed at determining the concentration of specific ions in seawater and relating them to chlorinity.
30/66 History of Chemical Oceanography
1925-1927/Meteor Expedition A German effort in the South Atlantic. The survey vessel conducted depth soundings, water temperature studies, took water samples, studied marine life, and conducted atmospheric observations. The Meteor was equipped with early sonar equipment with which it produced the first detailed survey of the South Atlantic ocean floor. The survey established that the mid-Atlantic ridge was continuous through the South Atlantic and continued into the Indian Ocean beyond Cape of Good Hope.
A chemist, Herman Wattenberg, was on board and performed some of the first routine photometric determinations of micronutrients, in addition to a study of the carbonic acid system. He also measured dissolved oxygen (Winkler titration) and phosphate to investigate the relationship between the distribution of phytoplankton and phosphate.
31/66 History of Chemical Oceanography
1925-1927/RSS Discovery Expedition The RRS Discovery was the last wooden three-masted ship to be built in Britain. Her first mission was the British National Antarctic Expedition, carrying Robert Falcon Scott and Ernest Shackleton on their first, successful journey to the Antarctic. Some photometric determinations of nitrate and nitrite were carried out for the first time at sea, in addition to salinity, dissolved oxygen, pH and phosphate. These measurements enabled George E.R. Deacon to deduce the movements of water masses in the South Atlantic and demonstrate that the upwelling of nutrient-rich waters is responsible for the high productivity of the Antarctic Seas.
Sir Ernest Henry Shackleton (1874-1922)
Captain Robert Falcon Scott 32/66 In 1966, at the instigation of the International Commission, the British National Institute of Oceanography (Southampton) and the University of Liverpool carried out the analysis of over 100 samples representative of major seas and ocean basins. These results are presented below.
33/66 GEOSECS The Geochemical Ocean Sections Study (GEOSECS) is one of the major programs of the International Decade (1970-1980) of Ocean Exploration, a cooperative, multi-national and multi-institutional study of the world oceans. The study was carried out between 1972 and 1978 and covered the Atlantic, Pacific and Indian Oceans. The objective was a global survey of radioisotope and other geochemical tracers accompanied by high precision measurements of temperature, salinity, density in both continuous and discrete sample profiles.
34/66 DSDP - Deep-Sea Drilling Project Initiated in 1972, this program lasted a little more than 10 years and was conceived to characterize the sedimentary sequences which could be recovered from drilling at various stations in deep-sea sediments of the Atlantic, Pacific and Indian Oceans. DSDP was almost immediately followed by plans to continue the drilling program.
D/V Glomar Challenger 35/66 36/66 ODP & IODP
Focused on specific problems related to paleoceanography and plate tectonics
37/66 The main aim of the WOCE was to acquire a high quality dataset, which represented the state of the oceans during the 1990s. These data are still used today to improve models of the ocean-atmosphere coupled system with the aim of improving our ability to forecast changes in ocean climate. They also provide a 1990s baseline against which to assess future (and past) changes in the ocean.
38/66 The Earth System
39/66 Earth System23_07.jpg Science
40/66 The Joint Global Ocean Flux Study was launched in 1989 as a Core Project of IGBP to address the question: How do ocean biological processes influence and respond to climate change?
JGOFS Objectives -To determine and understand on a global scale the processes controlling the time- varying fluxes of carbon and associated biogenic elements in the ocean, and to evaluate the related exchanges with the atmosphere, sea floor and continental boundaries -To develop a capacity to predict on a global scale the response to anthropogenic perturbations, in particular those related to climate change.
41/66 GLOBEC, a study of Global Ocean Ecosystem Dynamics, was initiated in 1990 by the Scientific Committee on Oceanic Research and the Intergovernmental Oceanographic Commission of UNESCO, and incorporated into the IGBP Core Element structure in 1995.The GLOBEC Science Plan was published in 1997, which set out the GLOBEC goal as:
“To advance our understanding of the structure and functioning of the global ocean ecosystem, its major subsystems, and its response to physical forcing so that a capability can be developed to forecast the responses of the marine ecosystem to global change”.
42/66 LOICZ (Land-Ocean Interaction in the Coastal Zone) LOICZ is a core project of the International Geosphere-Biosphere Programme (IGBP) and the International Human Dimensions Programme on Global Environmental Change (IHDP).
LOICZ aims to provide science that contributes towards understanding the Earth system in order to inform, educate and contribute to the sustainability of the world’s coastal zone. Therefore LOICZ seeks to inform the scientific community, policymakers, managers and stakeholders on the relevance of global environmental change in the coastal zone.
43/66 The International SOLAS (Surface Ocean - Lower Atmosphere Study) Project is an international research initiative comprising of over 1500 scientists in 23 countries. The SOLAS International Project Office (IPO) is based in Norwich in the United Kingdom, and the IPO coordinates and communicates with research teams all over the world. The projects primary objective is: "To achieve quantitative understanding of the key biogeochemical-physical interactions and feedbacks between the ocean and atmosphere, and of how this coupled system affects and is affected by climate and environmental change."
44/66 GEOTRACES is an international programme which aims to improve our understanding of biogeochemical cycles and large-scale distribution of trace elements and their isotopes (TEIs) in the marine environment. The global field programme will run for at least a decade and will involve cruises in all ocean basins run by a variety of nations.
GEOTRACES mission is: To identify processes and quantify fluxes that control the distribution of key trace elements and isotopes in the ocean, and to establish the sensitivity of these distributions to changing environmental conditions.
45/66 CLIVAR is the World Climate Research Programme (WCRP) project that addresses Climate Variability and Predictability, with a particular focus on the role of ocean-atmosphere interactions in climate. It works closely with its companion WCRP projects on issues such as the role of the land surface, snow and ice and the role of stratospheric processes in climate.
The challenges for CLIVAR are to develop our understanding of climate variability, to apply this to provide useful prediction of climate variability and change through the use of improved climate models, and to monitor and detect changes in our climate system.
46/66 CASES (2002-2005) Canadian Arctic Shelf Exchange Study 47/66 Objectives
Based on the general hypothesis that the atmospheric, oceanic, and hydrologic forcing of sea ice variability dictates the nature and magnitude of biogeochemical carbon fluxes on and at the edge of the Mackenzie Shelf, the major objectives of CASES are to assess:
• The role of hydrologic, oceanographic and meteorological processes in ice growth, decay and transport on the shelf and beyond. • The hydrodynamic (including ice and snow cover dynamics) control of Arctic shelf photosynthetic production and its export to the benthos and the pelagic food web. • The potential impact of increased UV radiation on biological productivity. • The role of microheterotrophs and mesozooplankton in transforming particulate and dissolved matter on the shelf. • The fluxes of particulate matter and carbon across the shelf to the deep basins. • The distribution of riverine and air-borne contaminants in the trophic web. • The potential impact of a reduction in ice habitat on birds and marine mammals. • The decadal and millennial variations in ice cover and their impact on ecosystem productivity. • Physical and biological measurements will also be used to constrain and calibrate: regional models of climate and ice dynamics in the western Canadian Arctic as well as biophysical models of the carbon flows on the Canadian Arctic shelf.
48/66 49/66 Geneviève Bernier 50/66 51/66 Circumpolar Flaw Lead Study
• Project Title: The Circumpolar Flaw Lead System Study
• Region of Study: Southern Beaufort Sea
• Description: This project examined the importance of climate processes in changing the nature of a flaw lead system (a unique area where open water persists throughout the winter) in the Northern Hemisphere, and the effect these changes have on the marine ecosystem, contaminant transport, carbon fluxes and greenhouse gases. The project required the Canadian Research Icebreaker CCGS Amundsen to spend the winter in the Banks Island flaw lead in the Southern Beaufort Sea.
• Platform: CCGS Amundsen
• Project Leader: David Barber, University of Manitoba
52/66 M Mooring/Full Station
F Full Station B Basic Station N Nutrient Station C CTD Station
53/66 • Project Title: Investigation of the Effect of Climate Change on Nutrient and Carbon Cycles in the Arctic Ocean
• Region of Study: Beaufort Sea
• Description: This study provided crucial information that enabled scientists to better predict the effect of changes in temperature, ice cover and fresh water discharge on the productivity, ecosystem structure and carbon sequestration capacity of the Arctic Ocean. This information also helped predict the impact of climate change on the socio-economic sustainability of northern Canadian communities.
• Platform: CCGS Amundsen
• Project Leader: Roger Francois, University of British Columbia
54/66 Cruise Plan
55/66 MALINA (2007-2008)
• Project Title: Fate of organic carbon in the Mackenzie River system: influence of climate change on primary productivity, microbial activity and photo-oxidation of organic matter.
• Region of Study: Beaufort Sea
• Description: The general objective of the proposed study is to determine the impact of climate change on the fate of terrestrial carbon exported to the Arctic Ocean.
• Platform: CCGS Amundsen
• Project Leader: Marcel Babin, Villefranche-sur-mer, now at Université Laval (Québec City)
56/66 57/66 58/66 Average fCO2 (µatm) in the surface mixed layer (0-15 m) calculated from pH, At and DIC measurements carried out on Legs 1 and 2 of CASES (late December through early June, 2004).
59/66 Example of water mass distribution in the Amundsen Gulf
Summer 2004 CASES Leg 8
TA (µmol kg-1) Depth (m) Depth (m)
Temperature (°C) δ18O (‰)
Salinity ƒCO2 (µatm) 0 50 100 150 0 50 100 150 Distance (km) Distance (km) 60/66 Example of water mass distribution (OMP analysis)
Summer 2004 - MW et SIM (0-20 m) CASES Leg 8 - PML (0-80 m)
- PW (80-200 m)
- ALW (>200 m)
PML
% Depth (m) Depth (m)
MW PW
SIM ALW % Distance (km) Distance (km) 61/66 • Project Title: Biogeochemical and tracer study of a rapidly changing Arctic Ocean
• Region of Study: Canadian Arctic Archipelago (CAA) and the Beaufort Sea • Description: An international, pan-Arctic field study to measure a suite of chemical tracers that provide information on key biological, physical and chemical processes in the Arctic Ocean and CAA. Chemical measurements will be coupled to detailed surveys of water mass structure and circulation, and the results incorporated into computer models predicting Arctic Ocean responses to climate change and other human-related disturbances.
• Platform: Amundsen
• Project Leader: Roger Francois, University of British Columbia 62/66 Cruise Plan
Tentative cruise tracks for the 2015 international Arctic GEOTRACES program, including US, UK, Sweden (Sw), Germany (D), France (Fr), Russia and Canada (Ca).
63/66 64/66 65/66 66/66