Schließen
Noting in Figure 1 the cardinal direction arrows in the upper left hand corner of the block diagram and the coast labels, the west boundary of the ocean basin is the land’s ________ coast
It can also be seen that the eastern boundary of the ocean basin is the adjacent land’s ________ coast.
In Figure 1, imagine you are in a boat positioned at the tail end of the arrow showing wind and looking in the direction towards which the wind is blowing. At that location, the wind is blowing towards the
In the same view, the direction of the near-surface ocean flow is towards the ________
In the same view, the coastal downwelling would be expected offshore of the ________ while coastal upwelling would be happening offshore of the opposite coast.
This forces seawater westward, where it piles up and sea level rises. As the model shows, this produces ________ in the western portion of the ocean basin. At the same time, the Ekman transport causes a lowering of sea level to the east, where seawater moves in the opposite vertical direction.
Predict the flow direction of near-surface water produced by wind blowing in the opposite direction in the same hemisphere. Go to Time :24 to verify (or refute) your prediction. The model shows that the Ekman transport is 90 degrees to the ________ of the wind direction and towards the east.
As the model shows, this eastward flow results in ________ in the eastern portion of the ocean basin. At the same time, the Ekman transport causes a lower of sea level to the west, causing seawater to move in the opposite vertical direction.
Now apply the Ocean Basin Model to the Southern Hemisphere where the Coriolis effect is opposite in direction to that in the Northern Hemisphere, that is, causing Ekman transport to flow at 90° to the left of the wind direction. Start the video at Time :48. In this setting the wind is blowing towards the south and the near-surface flow of water is towards the ______, or to the left when viewed from a boat located at the tail of the wind arrow and looking towards the direction the wind is blowing.
In the setting just described, coastal ________ is produced along the western coast of the land mass to the east.
Now view the video starting at Time 1:12. In this Southern Hemisphere ocean basin, a wind flowing towards the north produces Ekman transport of seawater that results in ________ in the western coastal areas of the Ocean Basin Model. Additionally, the opposite vertical flow of seawater appears in eastern coastal areas.
Coastal upwelling of nutrient-rich water stimulates the growth of marine autotrophs (e.g., phytoplankton) that support marine food webs and fisheries. According to the Ocean Basin Model (see video settings starting at Time :00 and :24), a wind blowing towards the _______ along the Northern Hemisphere western coast of Africa would produce upwelling and increased productivity.
According to the Ocean Basin Model, a wind blowing towards the _______ along the Southern Hemisphere western coast of South America would produce downwelling. When the wind transports near-surface water towards a coast, the warm surface layer thickens and sinks, decreasing marine productivity.
Along the coast of central and northern California, prevailing surface winds blow from north to south in the summer and from south to north in the winter. Based on the model, the season when cold coastal upwelling water cools the overlying air to saturation and produces frequent fog is ________.
In the Northern Hemisphere’s tropical latitudes, the trade winds blow towards the southwest. This wind stress on the ocean surface produces Ekman transport of water 90 degrees to the right of the direction of motion and towards the northwest. This results in surface-layer ocean water flowing ________ the equator.
In the Southern Hemisphere’s tropical latitudes, the trade winds blow towards the northwest. Because this is in the Southern Hemisphere, the wind stress on the ocean surface produces Ekman transport of water 90 degrees the left of the direction of motion and towards the southwest. This results in surface-layer ocean water flowing ________ the equator.
The surface-layer water flows described in the previous two items indicate that during average trade-wind conditions the surface waters along the equatorial Pacific are ________.
Consequently, the open-ocean equatorial Pacific experiences ________. This is consistent with the relatively high marine productivity observed there and the resulting biogenous sediment deposits in the equatorial Pacific. Refer back to Figure 1 in Investigation 4A for the distribution of siliceous radiolarian oozes in that part of the Pacific Ocean.
In Figure 2, at middle and low latitudes of both the Southern and Northern Hemispheres, coastal areas tend to be ________ productive than mid-ocean areas.
Not all productive ocean areas are due to upwelling. Particularly productive coastal regions are those at the mouths of major rivers delivering large amounts of nutrients with their discharges. Referring to Figure 1, observe the coastal areas where the U.S. Mississippi River enters the Gulf of Mexico, the Amazon River of northern Brazil, the Platte River of Argentina, the Congo River of equatorial Africa, and the Indus and Ganges Rivers of the Indian subcontinent enter the ocean. The chlorophyll shadings at these locations indicate relatively ________ concentrations.
At high latitudes, in the Arctic and Antarctic, relatively high productivity is seen in red and orange shadings in Figure 2. These coastal waters usually exhibit dramatic episodes of high productivity in the Northern and Southern Hemisphere spring seasons. The dominant factor in causing these explosions of productivity is the reappearance of ________. The detailed measurements will be covered more in Investigation 10A.
Figure 2 also shows that in the broad expanses of the Pacific Ocean, marine productivity along the equator is ________ marine productivity in the subtropical ocean basins to the north and south.
As you determined in the first part of this investigation, the relatively high productivity along the equator is due to ________ as surface waters flow away from the equator due to the effects of the Northern Hemisphere northeast trade winds and the Southern Hemisphere southeast trade winds combined with a weak Coriolis Effect.
Scroll down the CBOFS website and click on “Nowcast” under the Water Level Icon . The water level animation which appears displays the most recent water levels in local time in ________–hour intervals.
Water levels are reported in the animation relative to the MLLW (Mean Lower Low Water) in feet and are color coded in the animation with the highest water levels (indicating high tide) most likely represented by ________.
Allow the animation to run while following the progress of either high water levels (high tides) or low water levels (low tides) through Chesapeake Bay. You can use the control bar under the map to stop the animation and then click the “Next” button to set your own viewing pace. The animation shows the tides moving through the estuary ________ the mouth of the Bay. Figure 2 shows water level changes during one high tide’s journey through the Bay.
Figure 2 presents a sequence of three CBOFS Nowcast maps on 27 February 2017 showing the progress of a high tide as it traveled the length of the Bay. The high tide’s height color-coding at the mouth of the Bay was yellow/light green. When it reached mid-bay, it was green/blue, and by the time it was at the bay-head near Baltimore it was blue/green. The times shown below the maps, indicate it probably took about ________ hours for the high tide to travel the entire length of the Bay
Mentally draw vertical lines on Figure 3 to represent the same times of the water level Nowcast maps in Figure 2. The times (Local and EST) on the two figures are the same. The comparison of the 0800 EST 27 February 2017 Water Level Nowcast map in Figure 2 with the predicted and observed water levels in Figure 3 for the same time are consistent in showing the presence of a ________ tide near the mouth of the Bay.
Knowing the direction of movement of tides in Chesapeake Bay as seen in the Water Levels Nowcast animation, Figure 2 reveals that this tide (identified in Item 5) progressed about ________ of the Bay in the subsequent six hours.
Both Figures 2 and 3 show that by 1400 EST 27 February 2017, Kiptopeke and other locations near the mouth of the Bay were beginning to experience ________ tide conditions.
Figures 2 and 3 show that, by the time the tide observed at the mouth of the Bay at 0800 EST on 27 February 2017 had traveled essentially the full length of Chesapeake Bay, Kiptopeke and other locations near the mouth of the Bay were experiencing their next ________ tide.
The water levels and time information presented in both figures indicate that Chesapeake Bay experiences ________ tides.
chesapeake Bay experiences currents ________ the Bay.
Play the animation and note the direction of currents in the lower half of the Bay over the period of a day. When at their strongest, currents moving northward in the lower half of the Bay tend to be closer to the shore to the east. This occurs because the Coriolis Effect (due to Earth’s rotation) pulls the water to the ________ as it advances.
The color coding shows that the salinity of the open Atlantic near-surface water has values near ________.
The color coding shows that the most northerly reaches of the Bay have salinities near ________.
The pattern of near surface salinities throughout the Bay reveal that waters entering the Bay from the ocean and from rivers flowing into the Bay ________ mix.
Play the salinity animation and look for flows of higher salinity water into the Bay. When they occur they tend to flow northward along the ________ side of the Bay. This is consistent with your finding in Item 11 above.
easonal changes in the influx of freshwater from rivers and streams have implications for the salinity gradient in Chesapeake Bay. In spring, rains and snowmelt in the Chesapeake Bay drainage basin increase the discharge (cubic meters per second of flow) of the rivers and streams draining into the Bay. On the other hand, in autumn, precipitation in the drainage basin tends to be lighter. On this basis, we would expect the Bay waters overall to be ________ salty in spring than in autumn.
Because of sediment deposition, the water is relatively shallow in most parts of the Bay. Hence, sunlight readily penetrates to the bottom and is available for ________ which supports an abundant growth of grasses and other rooted aquatic plants.
These plants are ________ that provide a broad base for the Bay’s food chains and habitats for many organisms.
The pattern displayed in the Figure 4 top left January vertical hydrographic section indicates that the water is generally ________. This vertical temperature profile is characteristic of shallow waters, especially with salinities of 24.7 or higher as described in Investigation 3B, undergoing net cooling through loss of heat to the atmosphere. The July view shows temperature stratification with warmest water at the surface.
The Bay’s salinity varies vertically. In the middle hydrographic sections, it can be seen that the most saline water is generally at the ________ depths. Greater stratification of salinity is evident in the July section.
The fact that water throughout the Figure 4 vertical cross-sections have salinity values that are lower than those of the nearby open ocean implies that ________ mixing has occurred involving all the water at the mouth of the estuary.
In general, the near-surface water is fresher on the left (west) side of the profiles in Figure 5. One factor that contributes to this freshening is the fact that more rivers and streams enter from the west side of the Bay than from the east side. Another factor is the Coriolis Effect. As noted in Item 11, the Coriolis Effect causes water currents to turn rightward, so fresh water flowing southward down the Bay curves rightward toward the ________ side of the Bay.
The bottom hydrographic sections depict the vertical density pattern. The vertical density distribution in January is consistent with the dominant effect of salinity on water density (the temperature pattern is isothermal). With increasing salinity, the density of water ________. The July section shows the combined temperature and salinity patterns at that time of year result in greater density stratification across the Bay.
As mentioned earlier, the influx of water into the Bay from all sources is about half fresh water and about half seawater when averaged over time. Consequently, in Figure 4, it can be assumed that the denser bottom water is primarily seawater in origin that is probably flowing toward the ________.
Simultaneously, the less dense near-surface water is a mixture containing greater amounts of fresh water that is flowing toward the ________.
