6. Preparing to Depart - Marine Conditions

Main Menu	6. Preparing to Depart - Marine Conditions
Expedition Menu 1. Welcome 2. The Idea 3. Boarding 4. Ship Tour 5. Back Deck 6. Preparing to Depart 7. Leaving 8. Meeting 9. Bay-Delta-Estuary 10. Navigating 11. The Survey 12. First Data 13. The Mosaic 14. Visualizing 15. Hazards 16. Disposal Site 17. Sediment Map 18. Compare 19. Future Studies 20. Final Meeting		The conditions in the bay and at sea can change quickly during the day. Consequently, before leaving the dock, the captain of the ship and members of the ship’s crew need to examine the most recent marine conditions, including the status of the tides, wind, currents and marine (weather) forecast. The scientific party also needs to take note of these conditions as each may cause the survey plan to be modified at the last minute. Join in this work by clicking on each of the following links while transferring the appropriate information to your worksheet.
	Tide Gauges Around the Bay Image and Information Courtesy of USGS - SFPORTS	What is the water level in the bay? -The water depth in the bay changes throughout the day with the ebb and flood of the tides. - Find the station closest to the current position of the ship (at the dock) and the station nearest to the Golden Gate where we will be conducting the survey of the bay floor. Next, examine a table of the data given in the above image. In the table on your worksheet, write down the station name, date and time of the measurement, height of tide, whether the water is rising, slack, or falling. How do you think that this information may be used by the captain in deciding when to leave the dock? You may want to pause the audio player at this point.
	Winds Around the Bay From USGS SFPORTS website (by SJSU Meteorology Dept)	Remember to restart audio, if it has been paused. What is the wind speed and direction? The wind on the San Francisco Bay can be very strong as the Golden Gate forms one of the few openings in the Coastal Range (mountains), which separates the Pacific Ocean from the rest of North America . The map below shows the wind direction and speed on the bay, The arrows, technically called vectors, show the direction of the wind over the bay area with the length of each arrow representative of the wind speed. Click on the map of the wind direction and speed for the a display of the current winds on the bay in a second window of your browser. If you want the "exact" wind direction and speed at any location, click on any arrow on the map and look at the display below of the lower right corner of the image in the pop-up window. On the map in your worksheet, draw at least seven arrows to show the direction of the wind over the bay area – make the length of each arrow representative of the wind speed Summarize in two-three sentences the patterns of the winds You may want to, once again, pause the audio player at this point.
	Tidal Currents Around the Bay	Remember to restart audio, if it has been paused. What are the currents in the Bay at the present time (see image at left or click here)? The ebb and flow of the tides result in a large variation in currents in the bay over a 24 hour period. With the falling tide, the currents are directed out of the bay, and with the rising tide, the currents are directed into the bay (obviously). The currents are strongest at the Golden Gate since it forms a restriction between the large volumes of water mixing between the Pacific Ocean and the bay. Draw at least seven of these vectors on the map in your expedition worksheet to summarize the direction of tidal currents in the bay at the present time. If you click on the current map to the left, an animation of the chnanging tidal currents over the previous 24-hour period will be displayed in the second window of your browser. From USGS SFPORTS website CClick on map to view animation of currents over 24-hour period from USGS SFPORTS website You may want to, once again, pause the audio player at this point.
	Remember to restart audio, if it has been paused. Last, but certainly not least, access the marine forecast. What is the marine weather forecast for the region of the survey.? (Summarize the forecast in a few sentences in your worksheet)
Created By: Don Reed Dept. of Geology San Jose State University ©Copyright 2008 Last Updated on Sept. 15, 2008		We have stowed our gear, had lunch, made a tour of the ship, and have collected the data on conditions on the bay – time to begin our work!