Integrating Oceanographic Data Sets in Introductory Course Labs P L Guth , Department of Oceanography, U.S. Naval Academy, Annapolis MD 21402-5026 ph. 410-293-3561 Internet: pguth@charleston.nadn.navy.mil Poster from 1994 Ocean Sciences Meeting, sponsored by AGU & ASLO, San Diego, 24 Feb 94. Abstract published (so far) only in handout given out on site with the meeting program. Abstract We have developed a series of public domain microcomputer labs for our introductory oceanography courses that integrate widely available geophysical data sets with basic text coverage. Programs for all labs run on industry standard MS-DOS microcomputers, and use the same routines and menu-driven user interface, so that students can focus on interpreting data rather than program mechanics. Much of the data comes on CD-ROMs from government agencies, but we have produced subsets which do not require a CD-ROM drive or disk for each student, reduce the amount of data to a manageable level for students, increase program performance, and can be transported on floppy disks to set up the labs. Data sets extracted from CD-ROM include: GLORIA sonogram mosaics; gridded bathymetry differentiating active and passive margins; integrated bathymetry, gravity, and magnetics grids showing their relations with different plate boundaries; CTD casts as depth plots, T-S plots, and contoured profiles showing latitudinal and seasonal variation in water masses, sound velocity, dynamic topography and surface currents; MCSST data showing seasonal changes and large scale features of ocean circulation; CZCS data showing patterns of ocean productivity; GEOSAT data showing geoid variability and wind and wave patterns; SSMI and SMMR ice concentration grids showing sea ice patterns; and DSDP and ODP results showing the age and lithology patterns of deep sea sedimentation. Additional labs demonstrate plate tectonic reconstructions and motions, tidal patterns and partial tide computations, wave motions, and beach profile response to changes in the wave climate. These labs cover the spectrum of topics included in introductory oceanography classes, and allow students to manipulate actual data and explore relationships. Many of the labs have additional capabilities suitable for more advanced classes. Reasons to Download Data from CD-ROM 1. Preclude need for CD-ROM for each student. 2. Preclude need for CD-ROM drive for each student. 3. Combine data from several CD-ROMs. 4. Subset data--smaller data sets, faster access. 5. Improve data access speed (CD-ROM is slow). 6. Move data sets on floppy disk. 7. Reformat data for more compact storage or faster access. Program Operation. 1. Menu-driven. 2. Reasonable defaults always suggested. 3. Error-trapped. 4. Graphical selection of data points with the mouse. 5. Same interface and routines for all programs. Graphics Output. The color prints on these posters are copies of screen output that were saved in BMP format and then printed on a HP500C ink jet plotter with Microsoft Word for Windows (any other output device with a Windows driver could be used, as could other Windows program including PaintBrush). The programs have the capability to perform screen dumps directly to HP laser printers and most 8-pin and 24-pin dot matrix printers, as demonstrated by samples. Hardware Requirements. 1. 80386 or better CPU 2. 2 Mb free RAM (programs run in protected mode) 3. VGA color monitor (some options can run in SVGA mode) 4. Mouse optional but highly recommended 5. Optional math coprocessor highly recommended for some programs. 6. Optional HP Laser or Dot Matrix printer for hard copy output. 7. Optional Novell network simplifies distribution of programs to multiple computers. Typical Introductory Course Chapters (cf. Thurman, Gross) With Possible Labs Global Plate Tectonics *Continental Drift Program: choice of total reconstruction poles from Cox & Hart (1986) or Duncan & Richards (1991); continental outlines have 400-1300 points. *Marine Geophysics Trainer with relations of bathymetry, gravity, and magnetics. Data extracted from Geophysics of North America CD-ROM, ETOPO5 and 2.5' gravity and magnetics. Earthquake distributions, both North America since 1700's (Geophyics of North America CD) and worldwide during 1980's (Global Relief CD) Transform faults and marine magnetic anomalies (Global Relief CD) GEOSAT data for ridges and trenches Marine Provinces *U.S. EEZ multibeam bathymetry showing active and passive margins, submarine canyons (Global Relief CD) *GLORIA imagery (USGS CDs) Marine Sediments DSDP/ODP drilling records with ages and lithologies (lithologies entered by hand, about 400 holes done), ages from CDs Properties of Water *CTD data to prepare T-S diagrams; temperature, salinity, sound velocity depth plots and contoured profiles; data from NODC CD-ROMs Air-Sea Interaction Wind patterns observed by GEOSAT Seasonal sea ice around Arctic and Antarctic--NASA and NSIDC CD- ROMs Annual MCSST patterns--JPL CD-ROMs Ocean Circulation *Calculation of average density and sea surface slope and geostropic currents from CTD data: western boundary currents, equatorial currents, Antarctic currents (NODC CD- ROMs) Waves GEOSAT data showing variation in significant wave height with season and latitude Group speed simulation Tides Different types of tides and partial tides The Shore Seasonal bar profiles and their relation to wave climate, using data from Lee, G.-h., and Birkemeir, W.A., 1993, Beach and nearshore survey data: 1985-1991 CERC Field Research Facility: Waterways Experiment Station Technical Report CERC-93-3. Simulation of beach profiles by changing wave parameters, after Martinez, P.A., 1987, WAVE: program for simulating onshore- offshore transport in two dimensions using the Macintosh computer, Computers & Geosciences, vol.13, no.5, p.513-540. Biologic Productivity Productivity patterns from CZCS data (JPL CD-ROMs) *Available for FTP on internet now; others will be added soon. We actually teach a two semester introductory oceanography course sequence for our majors using the Open University series of texts. We have a number of underway labs each semester with our research vessel. We use some of these labs in the introductory sequence, and others in more advanced courses. I am working on three fronts for distribution: 1. Getting a CD-ROM with the data and programs; this is the only feasible way to distribute some of the data sets (CZCS, MCSST, GLORIA, ice concentrations). This will probably not be soon. 2. Getting some of the programs and data on the Internet. Space may limit what I can post; two programs are there now. 3. Some programs can be distributed via floppy disk, if you send me a sufficient quantity. I must carefully craft a batch file for each program that will insure that all support files go with the program. If you would like programs, let me know which ones and I will figure out how many disks will be required. For those that cannot go via floopy disk, it is the data files that limit, and I have or soon will have data extraction routines so that you can get your own data files from the original CD-ROMS. I am working on consolidating the lab instructions that I use for the exercises. These will undoubtedly require modification for other people to use; I would greatly appreciate comments or suggestions. There are some programs that I have not yet personally used for instructional purposes in a lab. Selected CD-ROMs with Oceanographic Data Sets National Aeronautics and Space Administration Goddard Space Flight Center, [undated], SMMR Polar Data: Vol.1-6, SMMR North Polar Radiances; Vol.7 North Polar Radiances and Arctic and Antarctic Sea Ice Concentrations for the Period 25 Oct 78 to 20 Aug 87; Vol.8-12, SMMR South Polar Radiances; USA_NASA_971_SMR_0001 to USA_NASA_971_SMR_0008. National Aeronautics and Space Administration, [undated], PO.DAAC merged geophysical data record from the TOPEX/Poseidon Mission: CD-ROM POMGA_001_1 (Cycles 1 and 2) to POMGA_020_1 (Cycles 39 and 40). National Aeronautics and Space Administration, [undated], SMMR Polar Data: Vol.1-6, Monthly mean distribution of satellite-derived sea surface temperature and pigment concentration: Vol.1 to Vol.5, USA_NASA_JPL_PODAAC_A001 to USA_NASA_JPL_PODAAC_A005. National Geophysical Data Center, [undated], Data from the Deep Sea Drilling Project, Vol.1-Sediment/Hardrock & Reference Files, and Vol.2, Downhole Logs & Underway Geophysics. National Geophysical Data Center, [undated], Geophysics of North America. National Geophysical Data Center, [undated], Global relief data. National Geophysical Data Center, [undated], Ocean Drilling Program, Disc 1a version 1.01-Sediment/Hardrock & Underway Geophysical Data from Legs 101-129, and Disc 1b G.R.A.P.E. data from Legs 101-129. National Oceanographic Data Center, [undated], Global ocean temperatures and salinity profiles: CD-ROM NODC-02 (Vol.1, Atlantic, Indian, and Polar Oceans), and CD-ROM NODC-03 (Vol.2, Pacific Ocean). National Oceanographic Data Center, [undated], U.S. Navy Geosat altimeter data (GDRs) from the Geodetic Mission, 30xS-72xS: CD-ROM NODC-18 (Disc 1, 30 Mar 1985 to 31 Dec 1985) and CD-ROM NODC-19 (Disc 2, 1 Jan 1986 to 30 Sep 1986). National Oceanographic Data Center, [undated], U.S. Navy Geosat altimeter data (T2 GDRs) from the Exact Repeat Mission: CD-ROM NODC-04 (Disc 1, Day 312 1986 to Day 099 1987), CD-ROM NODC-05 (Disc 2, Day 100 1987 to Day 263 1987), CD-ROM NODC-06 (Disc 3, Day 264 1987 to Day 067 1988), CD-ROM NODC-07 (Disc 4, Day 068 1988 to Day 247 1988), CD-ROM NODC-08 (Disc 5, Day 248 1988 to Day 085 1989), and CD-ROM NODC-09 (Disc 6, Day 066 1989 to Day 364 1989). National Snow and Ice Data Center, [undated], DMSP SSM/I Brightness Temperature Grids: Vol. 1 (870709 to 870930) to Vol.18 (911001 to 911231). National Snow and Ice Data Center, [undated], DMSP SSM/I Ice Concentration Grids: Vol. 1 & Vol.2. Naval Oceanography Command Detachment Ashville, 1992, U.S. Navy Marine Climatic Atlas of the World, Version 1.0. U.S. Geological Survey, [undated], GLORIA Data, Gulf of Mexico. U.S. Geological Survey, [undated], GLORIA East Coast: Disk A, Image Maps, and Disk B, Data Files. U.S. Geological Survey, 1991, GLORIA Imagery and bathymetry from the U.S. EEZ off Washington, Oregon, and California: Open File Report 91-396. Figures with these captions were shown in San Diego. They indicate the types of output possible with these programs. Figures, Clockwise from Upper Left. 1. World map with earthquakes of the 1980's in red, fracture zones in magenta, and magnetic anomalies in green. Note the menu across the bottom of the screen. 2. Sound velocity profiles in the Pacific. Output from an HP Laser Jet. 3. Four months average productivity from the CZCS. 4. Three dimensional view of the Atlantic continental slope. Output from an Alps 8 pin dot matrix printer. Figures, Clockwise from Upper Left. 1. Continental reconstructions for two times in the Mesozoic. 2. One day's data with significant wave height from the GEOSAT Exact Repeat Mission. 3. Age data for a series of DSDP/ODP holes in the southern Indian Ocean. Figures, Clockwise from Upper Left. 1. One cycle's GEOSAT passes plotted on a contour map of bathymetry along the Aleutian trench. 2. Graph of short wavelength geoid anomalies, one GEOSAT pass over the Aleutian trench. 3. Registered profiles of bathymetry, and gravity and magnetic anomalies over the Aleutian trench. 4. Three dimensional view of the Aleutian trench. Note the volcanic arc, and the seamount about the be subducted. 5. Summer and winter maps of the sea ice extent around Antarctica. 6. Registered maps of bathymetry, and gravity and magnetic anomalies along the Aleutian trench. Figures, Clockwise from Upper Left. 1. T-S plot of four stations in the Pacific, showing latitudinal variation. 2. North-south profile of August temperature in the Pacific, showing the pool of warm water along the equator and the strong thermocline approaching the surface toward the poles. 3. Selected profiles from one year at Duck, North Carolina. Note the redevelopment of the bar after the severe late October storm. 4. Graph of MCSST over several years at two spots in the Eastern Pacific, one in each hemisphere. 5. San Francisco tide, shown as the sum of seven partial tides. 6. Waves of three periods travelling together. 7. Four months average MCSST data. 8. One year's significant wave height for Duck Carolina. Note the relationships with the beach profiles to the right, especially after the severe October storm. References: Cox, A., & Hart, R.B., 1986, Plate tectonics how it works: Blackwell, 392 p. Duncan, R.A., and Richards, M.A., 1991, Hotspots, mantle plumes, flood basalts, and true polar wander: Reviews of Geophysics, vol.29, no.1, p.31-50. SO231 General Oceanography Geostrophic Currents and Ocean Circulation Uses Program TS-PLOT. KUROSH: this data set consists entirely of data collected in August 1981, so it gives a synoptic view of the area around Japan at essentially one instant in time. The Kurishio current is a warm current in the western Pacific analagous to the Gulf Stream in the Atlantic. Where is the Kuroshio current? Why don't the surface temperatures clearly show this current? We will calculate the Kuroshio current as a geostrophic current, with a reference level at 1500 m. Go to highlight, depth, and select 1500 m to see which stations went deep enough to provide data that we can use. Go to highlight, average density, and select the two stations near N34, E141 that appear to be part of a NW trending transect. The program will give you the average density (sigma tee) between the surface and your reference level at 1500 m. Record the two densities. Which way does the sea surface slope? Which way will the geostrophic current flow? Ans: Sigma tee 26.377 (NW) and 26.300 (SE) Go to Map, Distance, and get the distance between the two stations. Ans: 83.40 KM Calculate the geostrophic current, using the method explained on pages 50-51 of the text and question 3.7. Ans: 0.16 m/s Calculate the difference in height of the sea surface. Ans: 0.11 m Look at the two north-south profiles with stations over 1500 m deep. Look at the average densities along each profile, and predict which way the sea surface will slope and which way the geostrophic current will flow. REDSEA: this data set consists entirely of stations collected in the month of July. Note that some of the stations consist solely of deep data (below 1500 m). Arabian Sea water: 26xC, 36.0 PSU Indian Equatorial water: 28xC, 34.6 PSU South Indian central water: 24xC, 35.1 PSU Red Sea Water intermediate water: 22xC, 40.4 PSU Common water: 1.5xC, 34.7 PSU Antarctic bottom water: 0.2xC, 34.7 PSU Rescale the T-S diagram to 34-36 PSU, and 0-30xC. Plot the following water masses on the diagram: Arabian Sea, Common water, and Indian equatorial. Plot station S10E65 (S 10.683, E65.0167; it is the northernmost of two adjacent stations) on the diagram. Post the depths beside the plot. Print the diagram (if your computer does not have a printer attached, get your neighbor to print a copy for you). How does density change with depth at this station? Calculate the proportions of the three water masses at each of the following depths. See the discussion on pages 189-190 of the text book, or question 6.19 on p.208. 129 m: 228 m: 391 m: 2969 m: What is the name of the feature centered at 228 m depth? Is there any water at this station that could not be obtained by mixing the three water masses given? How might you explain this fact? Can you see any evidence of Red Sea intermediate water moving southward into the Indian Ocean? What is the depth of this water within the Red Sea, and what would its density make it do if it entered the northern Indian Ocean? Can you see any water within this region that could not be mixture of the water masses listed above? What characteristics of a water mass could not be obtained by mixing the masses listed above? Ans: S39E80, S38E65, S38E58, S37E55, and S37E51 have water at 1200-1500 m with 34.4 PSU which is too fresh to be derived from any of the listed water masses; it is probably Antarctic intermediate water, 4xC, 34.4 PSU; they require a source of lower salinity water to be adding to the Indian Ocean. SO231 General Oceanography Spring 1993 Geostrophic Currents and Ocean Circulation Uses TS-PLOT program. PACIFIC: this data set consists primarily of August data. We will look at an east-west transect. What happens to the thermocline along the equator in the Pacific? Which way will the winds blow along the equator? What will they do with the surface water? What happens to the average density of the top 1500 m of the water column along the equator? Which way will the sea surface slope along the equator? What will the Coriolis force do along the equator? Which way will the geostrophic current flow along the equator? PAC-EQ: Look at Fig. 5.1 on page 123 to help with this region near the equator in the central Pacific south of Hawaii. Draw a north-south profile across the equator, and contour the temperature in the upper 500 m of the ocean. Locate the equatorial divergence. At what latitude is it located? What characterizes it here? There is another divergence. At what latitude is it located? Which divergence shows a greater displacement of the thermocline? Look at Highlight, Average Density. Pick a 1000 m reference level, and accept the max and min density suggested. Along the north-south profile, where will the highs and lows in the sea surface topography be located? What geostrophic current(s) will result? Does this pattern look like the currents shown in the book on page 123? S-POLAR use with fig.5.22 on p.152 Look at the stations south of 70x latitude. Which way does the sea surface slope? Which way will the geostrophic current run? What current is this? Where is the West Wind Drift, as determined by the slope of the sea surface? Which way does the current flow? Where is the Antarctic Polar Front, and how could you recognize it? Can you pick out the Antarctic Divergence? What happens there? REDSEA use with fig.5.10, p.136 This data set consists of July data. Look at the density distribution in the upper 1000 m of the ocean, along the coast of Somalia and Arabia. Which way will the sea surface slope, and the geostrophic current flow? Is this to be expected at this time of the year? Can you find the equatorial convergence? REDSEA-3 use with fig.5.10, p.136 This data set consists of March data. Can you find the equatorial convergences? How does this situation compare tiht the July data? Marine Geophysics Exercise SO231, Spring 1994 We will be looking at three geophysical data sets (bathymetry, gravity, and magnetics) for three areas of the world code named ICE, ALE, and ORE. The data sets are named ICEBATH, ICEGRAV, and ICEMAG for the first area, and similarly for the other two. Bathymetry is the measurement of sea floor depths. The bathymetry (and topographic elevations above water) are expressed in meters. The gravity and magnetic values are expresses as anomalies, or departures from the expected values. This is because the differences in the earth's gravity or magnetic field are very small, and it is much easier to perform the subtraction from the expected value and just compare the differences. A positive anamoly means that the gravity (or the magnetic) field is larger than would be expected, while a negative value means it is less. Over the oceans the patterns are consistent and meaningful, and help verify the predictions of plate tectonics. The anomalies are expressed in terms of the field values at sea level. Both gravity and magnetics are important to the Navy, and both have been measured by satellite. The Navy has funded the GEOSAT satellite which had a classified mission to measure the earth's gravity field; data from that satellite is now available to scientists to compare with the older SEASAT mission. The gravity is measured in tenths of a milligal; each of these units corresponds to 10-4 cm/sec}. Since the normal value of gravity is about 980 cm/sec} (minor variation with latitude, and variation with elevation), we are measuring gravity at about one part in 107. These differences are large enough to cause ICBMs to miss their targets. The magnetic values for field intensity are measured in tenths of gammas. The earth's field varies from 25,000 at the equator to 70,000 at the poles, so again the anomalies are very small compared to the values of the field. The three regions selected each have a significant feature associated with them. You will be working to determine what that feature is, and how the gravity and magnetics compare with the feature. Using the program MGT, you can do the following operations with the data: 1. Select the area you want. The computer will show some information about the bathymetry, gravity, and magnetic data sets, and then draw a map showing the area. Note the magnetic data set is derived from ship data, and you can follow the paths taken by survey ships. 2. You will now have the following options: Contour: you can draw a contour map of any one of the data sets, covering any portion of the area you want. Oblique: you can look at a three dimensional view of part of any of the data sets. Profiles: you can superimpose profiles of all three data sets, over any line you desire. Wander: move the mouse cursor around and see the values for the three data sets as you move. Image, then Hide Menu: if the menu blocks the image, select this. Legends: if the map covers the legend, you can put the legend back on top. XIT: return to select another area. The text book will be a helpful reference for this exercise. See esp Fig. 2-1, 2-3, 2-16, and 2-20. (Open University Text Ocean Basins: Their Structure and Evolution. You can use the coordiates from the program and the maps in the book to locate where these data sets are located. AREA ALE: Use the WANDER command to locate, on the ALEBATH map, the points referred to in questions 1-3 below, so you have a general idea where on the map they are located. Then use the PROFILES command to see how all three fields (bathymetry, gravity, and magnetics) vary along one profile; select one that runs from about N55x56' W162x11' to N50x3' W160x17' (note this profile runs through two of the points you are asked about (#2 and #3), and perpendicular to another (#1)). When you are done with the profile, select the OBLIQUE command and set the front left corner at about N51x29' W162x26' and the right front corner at about N53x19' W164x5' (note that feature #1 runs front to back in the three dimensional view, and #3 is to the right of center about midway back). You can now select your own views to help answer the questions. 1. What feature is located between N52x27' W164x45' and N54x17' W156x8'? How does gravity correspond with this feature (larger or smaller than normal)? 2. What features are located at N55x25' W161x58' and N56x8' W159x22'? Note these features are above water; how are they related to the feature from question 1? 3. What feature is located at N52x53' W161x9'? Looking at the three dimensional picture of the feature (oblique diagram), what is about to happen to it? 4. Note the pattern in the magnetics from N51x52' W164x15' to N51x25' W158x17' to N47x40' W155x50'. What does it say about the ridge that created this seafloor? What is the age of this seafloor? If the spreading rate were 2 cm/yr, how far away should the ridge that created this seafloor be now? AREA ICE: 1. Note the major feature from N62x21' W25x14' to N55x52' W34x48'. What is this feature? Note that it comes above sea level to the NE; does this make sense? How does gravity correspond with this feature? How does the magnetic pattern correspond with this feature? 2. What is the feature from N52x34' W35x1' to N52x8' W30x28'? AREA ORE: 1. Note the major feature from N40x55' W145x to N40x15' W125x. a. Note the pattern of magnetic anomalies in this region; what was the orientation of the ridges that created the seafloor. b. North of this feature, in which direction does the seafloor get shallower? younger? Where is/was the ridge that created it? c. South of this feature, in which direction does the seafloor get shallower? younger? Where is/was the ridge that created it? d. Is there currently motion along this feature, and is it a plate boundary? e. What is the feature? f. How does gravity correspond with this feature? 2. Note a subtle feature from N47x43' W128x57' to N45x15' W130x11', and then offset to continue from N42x56' W126x23' to N40x15' W127x18'. What is this feature? SO231, General Oceanography I Spring 1994 GEOSAT Altimeter and Gloria Imagery For this lab, we will look at two kinds of data, both of which have been described in the book and lecture: GLORIA sonar imagery GEOSAT radar altimeter data, from the Exact Repeat Mission The altimeter data covers the Aleutian region and Iceland which we looked at last week, while the GLORIA data covers a region off the coast of Oregon on the Pacific coast. GEOSAT DATA To access this data, run the program MGT, which we used last week. Then select the "GEOSAT" option. Note the diamond pattern on the map formed by the satellite passes. The satellite has ascending passes (moving south to north) and descending passes (moving north to south), which cross the equator at a consistent angle. Note that when you graph this data (by latitude or longitude), you may have both an ascending and a descending pass on the same day, and that they may give two distinct curves from different parts of the region. If this becomes a problem, you can select to draw just the ascending or the descending pass. When picking what do display, you can choose: Raw Height: change in the sea surface measured by the satellite from a smooth ellipsoid, and are in cm. H (geoid corrected): the raw height with some environmental corrections; moisture and ionospheric effects can change the speed of light and thus the height. Geoid (short wavelength): raw height with environmental corrections, plus removal of the long wavelength geoid changes using a 10xx10x grid of the geoid from the Defense Mapping Agency. Area ALE Days 32 and Day 49 repeat the same orbit. How does the geoid determined on these two days compare when graphed (i.e. what is the difference between the two passes, and what could account for the differences)? (You may have to rescale the graph to answer this question.) Day 43 passes over the seamount we looked at last week. Can you see a geoid anomaly over this seamount? Is there an explanation for this based on what you read about geoid anomalies? How large is the anomaly over the Aleutian trench? How are you going to measure it when there appears to be a regional trend? Why does the anomaly change from one end to the trench to the other? How does the magnitude of the anomaly compare with the depth of the trench relative to the adjacent seafloor? Area ICE Days 66 and 83 repeat. What is the difference between the two days? Why would scientists want the orbit to repeat like this? Day 73 provides a good pass over the ridge. What is the difference in sea surface measured by the altimeter (the ridge crest is at about 60xN)? What is the elevation difference of the ridge at the point compared to adjacent seafloor? GLORIA IMAGERY To look at the GLORIA imagery, select the MICRODEM program. Then go to the "Satellite" option. BLANCGLR.IDX From "New" pick the BLANCGLR.IDX data set, which is located about N44.5x, W130x off the West Coast. Go to "Window" to see the overall image; you will be looking at every third pixel in every third row. You can continue with this overall view, or zoom in on parts of the image. Go to "Locate" to find the points listed. There are linear streaks from about x=834,y=0 to x=783,y=615, from about x=0,y=927 to x=1203,y=1005, and from about x=201,y=6to x=177, y=600. Do these look like features on the seafloor? What could they be? What is the grain of the seafloor on the top half of the image? What do you think could cause it? What happens in the bottom portion of the image? What do you think could cause it?