ISS009-E-17738
ISS009-E-17734
ISS009-E-11537
There are many remnants of ancient Athens preserved in the modern city, including the Acropolis (labeled above; also see the earlier ISS photograph, The Acropolis, Greece). During the Classical Period, Athens was an important Mediterranean city-state whose enduring political and military dominance of the region was only ended following the Peloponnesian War of 431-404 BC. Following a long succession of foreign rulers, Athens became the capitol of the current Hellenic Republic (Greece) in 1834. The 2004 Olympic Games this week mark a homecoming for the modern Games, which were first hosted in Athens in 1896.
This astronaut photograph includes areas of new construction or renovation for the Olympic Games, such as the Faliro Coastal Zone Olympic Complex and Helliniko Olympic Complex. The image also demonstrates the control of bounding mountain ranges (Mts. Aigeleos and Hymettos) on the western and southern expansion of the Athens urban area. However, polygonal regions of high brightness in and adjacent to the mountains attest to ongoing development and land use change in these areas as well.
The ISS-9 Space Station crew obtained this high-resolution image of the western Athens area in June of 2004, allowing for detailed observations of land cover and land use changes in the urban area.
ISS009-E-12329
The northern coastline of the Dominican Republic in this image is a major tourist attraction due to its extensive beaches and coral reefs. Besides recreational opportunities, coral reefs provide protection for bays and critical habitat for numerous economically important marine species.
Cabarete Bay, a popular destination for surfers and divers, is formed by a barrier coral reef. Increased development of the city of Cabarete and deforestation of upland regions has resulted in increased urban and sediment runoff into the bay and impacted the health of the coral reefs. Overfishing of the coral reefs during the 1980s has also contributed to a decline in ecosystem function.
Environmental stress on the Dominican coral reefs is not due solely to human activities. Three major hurricanes have hit Hispaniola during the last 25 years, leading to direct physical destruction of coral reefs as well as large sediment pulses into coastal waters from debris flows (mudslides) and slope failures. Paradoxically, tourism in the Dominican Republic has helped alleviate one aspect of stress on the reefs. Many fishermen now work in tourist hotels for higher pay, decreasing fishing pressure on the coral reefs.
ISS009-E-13366
Scientists use ice cores, an automated weather station, computer modeling, and images like these as tools to learn about the past and present activity of Kilimanjaro’s receding glaciers. One atmospheric scientist at the University of Wisconsin-Madison found clues that link reduced cloud cover to post-1880 decreased water levels in East African lakes. Lake evaporation indicates a decrease in both precipitation and cloudiness around Kilimanjaro. These two images illustrate the changes over time in snow cover at the summit as well as the current extent of the glaciers themselves. Light brown outwash channels from the northwestern flank icefield are particularly evident in the oblique photograph (top). While clear conditions over Kilimanjaro allow for the collection of spectacular images like these, the lack of cloud cover may be one cause for the glaciers’ retreat. The increased sunlight facilitates faster evaporation and less precipitation—thus, the land surface absorbs more incoming sunlight and, as it warms, the ice and snow melts at an accelerated pace.
Most scientists agree that the glaciers of Mt. Kilimanjaro will be gone by the year 2020, but there is less agreement as to why they are now receding. Climatologists are now studying current weather trends, environmental changes from the late 1800s, and historical records of the mountain climate compared with longer-term climate records at lower elevations. A correct interpretation of the ice core data may help provide an explanation for this glacial recession. The loss of Kilimanjaro’s permanent ice fields will have both climatological and hydrological implications for local populations who depend on access to melt water from the ice fields as a source of fresh water during dry seasons and monsoon failures.
Additional images of Mt.
Kilimanjaro:
Kilimanjaro
(Landsat 7)
Mount
Kilimanjaro, Tanzania (SRTM)
Melting
Snows of Kilimanjaro (Landsat 5 & 7)
Kilimanjaro-The
Shining Mountain (Space Shuttle STS 38)
Mt.
Kilimanjaro’s Receding Glaciers (Space Shuttle STS 97)
ISS009-E-9985
The modern delta is in intensive agricultural use for rice, fruit, and vegetables. White polygonal areas to the north and south of the Ebro River are paddy fields. The Ebro delta also hosts numerous beaches, marshes, and salt pans that provide habitat for over 300 species of birds. A large part of the delta was designated as Parc Natural del Delta de l’Ebre (Ebre Delta National Park) in 1983. A network of canals and irrigation ditches constructed by both agricultural and conservation groups are helping to maintain the ecologic and economic resources of the Ebro Delta.
This astronaut photograph, taken in partial sunglint, also shows the Ebro’s fresh water lens—the water density boundary between the upper layer of fresh water issuing from the Ebro River mouth and the saltier, denser Mediterranean Sea water. Diversion and impoundment of the Ebro River upstream has led to a decrease in water and sediment delivery to the delta. This decrease has led to increased erosion in some areas to the northeast of El Fangar Bay and along the southwestern shoreline of the delta.
ISS009-E-10382
The rectangular grid pattern disappears in the small streets of the original city center, situated along the Santa Cruz River (enters the view at lower left and exits in the top left corner). Moist air from Mexico and the Gulf of California frequently travels northwards along the Santa Cruz River corridor during the summer months. This moisture results in “monsoon” thunderstorms that help recharge the aquifers providing the majority of Tucson’s water.
Newer and less densely built-up neighborhoods in the foothills of the Catalina Mountains are designed to incorporate natural landscape features, and retain major washes with natural vegetation. This portion of the cityscape seen from space is consequently quite different from the main city grid. The foothills afford views of the city to the south and the mountains to the north and are major areas of development. Large white dots within the urban grid (blue arrows) are the reflective rooftops of shopping malls.
Tucson enjoys an important position along several major crossroads. Interstate highway I-10, which connects southern California to Florida, appears as a straight line running parallel with the Santa Cruz River northwest from Tucson in the direction of Phoenix. I-10 traverses a well-marked alluvial fan that extends from the Santa Rita Mountains to the southeast (fine drainage pattern lower center of the view) and exits the view at lower right. Highway I-19 is the straight line (lower left) leading south from the city center, between the Santa Cruz River and rectangular spoil heaps of nearby copper mines. I-19 connects Tucson with Nogales on the Mexican border.
ISS009-E-9987
Angular patterns on the coast represent the docks of Spain’s largest port, on the east side of the delta. Central Barcelona lies between the docks and dark, forested Montjüic mountain (upper right).The Olympic village, built for the 1992 Olympic Games, occupies the waterfront east of the docks, with the old city just inland. The Besós River, also channelized to control flooding, defines the eastern part of the city. The population of the city proper, roughly between the rivers—a distance of 20 km—is ~1.5 million, but the entire metropolitan region reaches 4 million.
An interesting feature captured in this photograph is a white linear condensation trail silhouetted against the sea (right of image). The shadow of the contrail lies to the north (just offshore the port). Large vessels and their wakes appear as dots offshore just south of the condensation trail.
ISS009-E-9839
This image highlights the generally arid setting of the Colorada River delta estuary at its terminus and at low tide. The Desierto de Altar occupies the right portion of the image. The extensive white salt flats to the southeast of the Cienega (wetland) de Santa Clara are clearly visible. This brackish wetland is a major stopover point for Pacific shore bird migrations and is maintained by groundwater pumped from the southwestern USA.The channel extending from the large island in the center of the image (Isla Montague) to the northwest is an inlet from the Gulf of California which formed after the Colorado River receded due to impoundment of water by Hoover (1935) and Glen Canyon (1964) dams. It crosses floodplain sediments (gray to dark brown) left by the original river. Gray-brown linear streaks extending southeast from Isla Montague into the Gulf are floodplain sediments mobilized by tidal surges and wave action rather than fluvial processes. Dark green areas bordering the channel, shoreline, and Isla Montague are riparian and estuarine vegetation.
Prior to impoundment of water from upstream dams the delta provided habitat for a wide variety of species including shrimp, corvina fish, and vaquita porpoise. Replacement of water into the delta from groundwater and upstream releases have helped to revive some of the preexisting habitat. This reinvigorated habitat also supports a local ecotourism industry within the delta region. Continuing drought conditions affecting the southwestern USA may decrease water delivery to the delta with significant impacts on both the ecologic and economic health of the region.
The ISS-9 Space Station crew obtained this high-resolution image of the Colorado River Delta on June 2, 2004, allowing for detailed observations of the delta and adjacent regions.
ISS009-E-9952
The narrow Strait of Gibraltar is the gatekeeper for water exchange between the Atlantic Ocean and Mediterranean Sea. A top layer of warm, relatively fresh water from the Atlantic Ocean flows eastward into the Mediterranean Sea. In return, a lower, colder, saltier layer of water flows westward into the North Atlantic ocean. A density boundary separates the layers at about 100 m depth.
Like traffic merging on a highway, the water flow is constricted in both directions because it must pass over a shallow submarine barrier, the Camarinal Sill. When large tidal flows enter the Strait, internal waves (waves at the density boundary layer) are set off at the Camarinal Sill as the high tide relaxes. The waves—sometimes with heights up to 100 m — travel eastward. Even though the waves occur at great depth and the height of the waves at the surface is almost nothing, they can be traced in the sunglint because they concentrate the biological films on the water surface, creating slight differences in roughness.
In this image, the tidal bore creates internal waves (top arrow) that propagate eastward and expand outward into the Mediterranean in a big arc (near bottom). Other features can be traced in the sun’s reflections. Linear and V-shaped patterns (bottom arrow) are wakes of ships, providing evidence for the heavy ship traffic through the narrow waters between Spain and Morocco.
Water features in the sunglint pattern appear to the astronaut to be extremely transient, visible only briefly (a few seconds) as the spacecraft passes rapidly overhead. Photographs from space of the ocean sunglint pattern are a tool for studying physical oceanographic and atmospheric processes and other phenomena that affect surface roughness.
references:
Internal
Waves, Strait of Gibraltar
Christopher O. Tiemann, Peter F.
Worcester, Bruce D. Cornuelle, Effects
of Internal Waves and Bores on Acoustic Transmissions in the Strait
of Gibraltar, Conference Proceedings from Internal Solitary Wave
Workshop, Victoria, B.C., Canada, October 1998. Woods Hole
Oceanographic Institution Technical Report WHOI-99-07
Oceanography from the Space Shuttle, Solitons,
Gibraltar
