[16], The weak deep-water exchange with the Atlantic Ocean is due to the small depth of the relatively flat Greenland-Scotland Ridge between Scotland and Greenland, an offshoot of the Mid-Atlantic Ridge. Covering 25,100 ha (over half the area of the whole atoll) the wetland ecosystem of Aldabra includes the extensive shallow lagoon inside the atoll, which is carpeted with lush seagrass beds and patchy coral reefs, the intertidal mud flats, the coral reefs outside the lagoon, freshwater pools, beaches, and 2000ha of mangrove stands. Whatever potable water is available, its quality is not good. (b) The water cycle is the process by which water continually changes its form and circulates between oceans, atmosphere, and land. [29] Since 1982,[30] satellites have been increasingly utilized to measure SST and have allowed its spatial and temporal variation to be viewed more fully. [32] These wavelengths are chosen because they are: The satellite-measured SST provides both a synoptic view of the ocean and a high frequency of repeat views,[35] allowing the examination of basin-wide upper ocean dynamics not possible with ships or buoys. [42] Later in the 17th century, Dutch ships started hunting bowhead whales near Jan Mayen; the bowhead population between Svalbard and Jan Mayen was then about 25,000 individuals. Imp.] Nutrients, such as those from fertilizers and pollution, wash off the land and into the water, causing algal blooms that block sunlight necessary for seagrass growth. Oceanographers use various definitions of the number to use as the mixed layer depth at any given time, based on making measurements of physical properties of the water. The salinity varies between 34.3 and 34.6 and is lowest in spring owing to the inflow of melted snow from rivers. All these factors make it somewhat difficult to compare satellite data to measurements from buoys or shipboard methods, complicating ground truth efforts. In a moist atmosphere, this lapse rate is 6.5C/km, while in an atmosphere with less than 100% relative humidity, the required lapse rate is 9.8C/km. A barrier layer is formed in the isothermal layer when salty water is subducted (i.e. Warned my father when we moved into our new flat. It increased in the 1920s owing to the milder climate and then collapsed in the following decades until 1970; the decrease was, however, at least partly caused by overfishing. The storminess was relatively high between 1880 and 1910, decreased significantly in 19101960, and then recovered to the original level. To the west, the Scotland-Greenland Ridge separates the Norwegian Sea from the North Atlantic. Q.4. [62] Whereas drilling at depths exceeding 500 metres has been conducted since 1995, only a few deep gas fields have been explored commercially. 1. It contains numerous trenches and irregular peaks, which usually have an amplitude of less than 100 metres, but can reach up to 400 metres. [7] Around the rim of the lagoon are the larger islands of the Atoll. (g) Malini leaned against the pole when she felt that she was going to faint. It takes the rain with it, causing extensive drought in the western Pacific and rainfall in the normally dry eastern Pacific. [2] Sharks, manta rays, and barracuda populate the seas surrounding the island. Q.2. The value of the worlds ecosystem services and natural capital (PDF) - Robert Costanza, Ralph DArge, Rudolf de Groot, et al. It is low tide when waterfalls to its lowest level and recedes from the shore. [26] A large network of coastal buoys in U.S. waters is maintained by the National Data Buoy Center (NDBC). This also reduced the population of cod a major predator of capelin as the herring was still too small in numbers to replace the capelin in the cod's diet. Aldabra is the world's second-largest coral atoll,[2] lying south-east of the continent of Africa. [32] Other endemic plants includes Pandanus aldabrensis, the Aldabra lily (Aloe aldabrensis) and a sub-species of tropicbird orchid, Angraecum eburneum. In a 2011 assessment, nearly one quarter of all seagrass species for which information was adequate to judge were threatened (endangered or vulnerable) or near threatened using the International Union for the Conservation of Nature (IUCN) Red List criteria. Temperatures rose between 1920 and 1960,[19] and the frequency of storms decreased in this period. For example seas around Japan and the eastern coast of North America. Inside a cold cyclone, 500hPa temperatures can fall as low as 30C (22F), which can initiate convection even in the driest atmospheres. Ans. [4]:1228 Land surface temperatures have increased faster than ocean temperatures as the ocean absorbs about 92% of excess heat generated by climate change.[5]. The lower delta plain is the middle of the delta. [58] Russia is planning to expand its offshore oil production in the Arctic, which should increase the traffic of tankers through the Norwegian Sea to markets in Europe and America; it is expected that the number of oil shipments through the northern Norwegian Sea will increase from 166 in 2002 to 615 in 2015.[59]. Be a Detective Ans. Q. Water is life. How do we classify ocean movements? The name Aldabra, originally Al-Hadra or Al-Khadra (with several variants), was given by Arab seafarers[3] for "the atolls harsh, sun-baked environment"; this name was included in the Portuguese maps of the 16th century. In fact, the oldest known plant is a clone of the Mediterranean seagrass Posidonia oceanica, which may be up to 200,000 years old, dating back to the ice ages of the late Pleistocene. The darker shades of green indicate more species are present. (i) Poles There is also a difference of about 10C between the sea and the coastline. It is because industrial effluents and untreated water of industries get mixed into streams and rivers. Strong sea currents, maelstroms, and especially frequent storms made fishing a dangerous occupation: several hundred men died on the "Fatal Monday" in March 1821, 300 of them from a single parish, and about a hundred boats with their crews were lost within a short time in April 1875.[38]. Ocean temperatures (more than 20 metres below the surface) also vary by region and time, and they contribute to variations in ocean heat content and ocean stratification. That means the impact could spread far beyond the agencys payday lending rule. Deltas' greatest importance to human activities, fish and wildlife lay in their characteristic highly fertile soil The red line is the density profile, black line is temperature, and the blue line is salinity. [8] The Norwegian Arctic cod mostly occurs in the Barents Sea and at the Svalbard Archipelago. (e) I am a zonal champion now declared the excited athlete. Pacific Ocean, body of salt water extending from the 60 S parallel in the south to the Arctic in the north and lying between the continents of Asia and Australia on the west and North America and South America on the east. Duarte TAns. It is also used to calibrate measurements from weather satellites. NOAA's GOES (Geostationary Orbiting Earth Satellites) satellites are geo-stationary above the Western Hemisphere which enables to them to deliver SST data on an hourly basis with only a few hours of lag time. But it's what they do in their native habitat that has the biggest benefits for humans and the ocean. Using coupled, atmospheric/ocean models and tuning the mixing to eliminate BLT for one year prior to El Nino, it was shown that the heat buildup associated with barrier layer is a requirement for big El Nino. This value is well above 16.1C (60.9F), the long term global average surface temperature of the oceans. in the northern Indian Ocean), or advection of salty water subducted in the subtropics (found in all subtropical ocean gyres). The standard procedure for determining the mixed layer depth is to examine the profile of potential temperature, the temperature which the air would have if it were brought to the pressure found at the surface without gaining or losing heat. The villagers built a chapel, in the middle of the badamier trees, using timber and steel; the chapel was considered an essential addition to the plantation houses and office buildings. Ans. Ans. 2. Aldabra was until recently free of introduced birds, but the introduced Foudia madagascariensis that was introduced to Assumption Island now occurs on Aldabra. Unfortunately, seagrasses are in trouble. Runion was later returned to France, and Mauritius gained possession of Aldabra as well as the rest of the Seychelles. (Hint: Her delta in Egypt is famous) This helps the ships to arrive at the harbour more easily. Some of the most successful restoration stories come from the Chesapeake Bay and coastal Virginia in the Eastern United States where, through 2014, the Virginia Institute of Marine Science has seeded 456 acres with 7.65 million seagrass seeds. Because the specific heat of ocean water is much larger than that of air, the top 2.5 m of the ocean holds as much heat as the entire atmosphere above it. Advertisement. It reaches a speed of 10 Sv (1 Sv = million m3/s) and its maximum depth is 700 metres at the Lofoten Islands, but normally it is within 500 metres. Answer the following questions briefly. Explain the water cycle with a neat and labelled diagram. Sexual Reproduction: Seagrasses reproduce sexually like terrestrial grasses, but pollination for seagrasses is completed with the help of water. Dead seagrass leaves also play an important role in coastal ecosystems. [45] The kraken also appears in Alfred Tennyson's poem of the same name, in Herman Melville's Moby Dick, and in Twenty Thousand Leagues Under the Sea by Jules Verne. Q. A number of the species that depend on seagrasses are important for commercial and recreational fisheries. [V. Some of these living and dead seagrass blades are also washed to other areas of the ocean, feeding organisms in ecosystems as far as the deep sea. To the south lies the European continental shelf and the North Sea, to the east is the Eurasian continental shelf with the Barents Sea. an outline map of the world. The shape of ocean basins and adjacent land masses influence the path of circulation. Thus most settlements in Iceland and Greenland were on the west coasts of the islands, which were also warmer due to the Atlantic currents. Ocean temperature of at least 26.5C (79.7F) spanning through at minimum a 50-metre depth is one of the precursors needed to maintain a tropical cyclone (a type of mesocyclone). Asexual Clonal Growth: Similar to grasses on land, seagrass shoots are connected underground by a network of large root-like structures called rhizomes. This article incorporates public domain material from websites or documents of the National Oceanic and Atmospheric Administration. [33] Other large animals of the sea are hooded and harp seals and squid. [4][9] A small settlement was established on Picard Island facing west near the beach. Introduction of invasive species was banned, faunal species were protected under law, and active research on the ecology and biodiversity of the atoll was undertaken by the Royal Society of London from the mid-1970s. [49] Systematic oceanographic research in the Norwegian Sea started in the late 19th century, when declines in the yields of cod and herring off the Lofoten prompted the Norwegian government to investigate the matter. Sediment washing into the water from agriculture and land development can also damage seagrass beds by both smothering the seagrass and blocking sunlight. Seagrasses are often called nursery habitats because the leafy underwater canopy they create provides shelter for small invertebrates (like crabs and shrimp and other types of crustaceans), small fish and juveniles of larger fish species. Antarctica is the only continent without seagrasses. This current originates in the North Atlantic Current and passes along the European continental slope; increased evaporation due to the warm European climate results in the elevated salinity. The most important products of the Norwegian Sea are no longer fish, but oil and especially gas found under the ocean floor. [7][27] While the terrestrial topography (spread over an elevation range of 08 metres (026ft)[26]) is rugged and dictated by the geomorphic conditions, the land surface comprises limestone of about 125,000 years age, which has uplifted many times above the sea level. This pattern generally increases nutrients for marine life in the region, and can have a profound effect in some regions where the bottom waters are particularly nutrient-rich. [3][4] The second is wind-driven currents, which create layers in which there are velocity shears. However, extensive hunting had wiped out the whales in that region by the early 20th century.[32]. Three extant species of lizards occur, the skink Cryptoblepharus boutonii and the geckos Phelsuma abbotti and Hemidactylus mercatorius. This process is often described and modelled as an example of Kelvin-Helmholtz instability, though other processes may play a role as well. Weather satellites have been available to determine sea surface temperature information since 1967, with the first global composites created during 1970. Thus in lakes where the surface gets very cold, the mixed layer briefly extends all the way to the bottom in the spring, as surface warms as well as in the fall, as the surface cools. (i) Water cycle [7][26] Eco tourism is controlled and introduction of invasive species is restricted. Since then, invasive Caulerpa has been found in California and southwestern Australia where eradication programs are in place to prevent its spread. The ocean current influences the temperature conditions of the area. [1], The Norwegian Sea is a transition zone between boreal and Arctic conditions, and thus contains flora and fauna characteristic of both climatic regions. The Indira Point in the Andaman and Nicobar Islands got submerged after the tsunami. [6], The coasts of the Norwegian Sea were shaped during the last ice age. Briney, Amanda. This is particularly clear off the Norwegian coast along Helgeland and north to the Lofoten Islands. For every seagrass species there is on average more than one associated threatened marine species. 5. These include 'Mangliye blan' or white mangrove (Avicennia marina) which grows to 12 metres (39ft), 'Mangliye lat' or black mangrove (Bruguiera gymnorhiza) which grows to 18 metres (59ft) in a conical shape, 'Mangliye zonn' (Ceriops tagal) which grows to 7 metres (23ft) with a buttressed trunk, and 'Mangliye rouz' or red mangrove (Rhizophora mucronata) which is the tallest species up to 20 metres (66ft) in height.[34]. The stronger the wind blows, the bigger the wave becomes. We should think about the ways of its conservation for our own sake. The deepest mixed layers (exceeding 2000 m in regions such as the Labrador Sea) are formed through this final process, which is a form of RayleighTaylor instability. Tides & Currents Products NOAA's Tides and Currents website, developed and supported by the Center for Operational Oceanographic Products and Services (CO-OPS), provides the following products. The first is the ocean waves, which act in two ways. Seagrasses can form dense underwater meadows, some of which are large enough to be seen from space. Q.2. M.A., Geography, California State University - East Bay, B.A., English and Geography, California State University - Sacramento. The rhizomes can spread under the sediment and send up new shoots. This has been observed most strikingly in the Baltic sea with the disappearance of cod due to overfishing and corresponding increases in smaller fishes and crustaceans which limited epiphyte-grazing invertebrates, resulting in seagrass decline. In order to fully appreciate the role deltas play in our larger ecosystem, it is first important to understand rivers. Thus, water is very essential and therefore we must conserve it. National Geographic stories take you on a journey thats always enlightening, often surprising, and unfailingly fascinating. in the western Pacific), monsoon related river runoff (e.g. Occasionally when some mesograzer species are at very high densities they can create thick masses of mucus and sediment tubes that block light to the seagrass leaves, and they can even eat the seagrass directly. As of 2019, there is an estimated 6.5 hm3 of crude oil in the Norwegian Sea, with an expectation to increase oil production in the region up until 2025. In lakes, temperature structure is complicated by the fact that fresh water is heaviest at 3.98C (degrees Celsius). As these areas continue to grow the water becomes shallower and eventually, landforms begin to rise above the surface of the water, typically elevating to just above sea level. King Harald Fairhair is credited with being the driving force to colonize these islands as well as others in the Norwegian sea. It has been estimated that in this way the world's seagrass meadows can capture up to 83 million metric tons of carbon each year. In addition to (or perhaps in defiance of) these human uses, river deltas boast some of the most biodiverse systems on the planet. [4], There are a variety of techniques for measuring this parameter that can potentially yield different results because different things are actually being measured. This die-off was so severe that a small snail specialized to live on eelgrass went extinct as a result. Seagrasses provide many important services to people as well, but many seagrasses meadows have been lost because of human activities. It is one of the two UNESCO World Heritage Sites in the Seychelles;,[55] and is managed by the Seychelles Islands Foundation (SIF). Ocean Literacy Essential Principles and Fundamental Concepts. [55] The countermeasures by the NATO countries resulted in a significant naval presence in the Norwegian Sea and intense cat-and-mouse games between Soviet and NATO aircraft, ships, and especially submarines. Q.12. After an international protest by scientists (known as 'the Aldabra Affair'),[13] however, the military plans were abandoned and the atoll instead received full protection. Q. [8] Compared with the deep waters of the surrounding seas, NSDW has more nutrients but less oxygen and is relatively old. [14], The Norwegian Sea is connected with the Greenland Sea and the Arctic Ocean by the 2,600-metre deep Fram Strait. Settling of the shelf after the separation of the continents has resulted in landslides, such as the Storegga Slide about 8,000 years ago that induced a major tsunami. [7] Sir David Attenborough called Aldabra "One of the wonders of the world", and it is also known as one of "crown jewels" of the Indian Ocean. Sea surface temperature (SST), or ocean surface temperature, is the water temperature close to the ocean's surface. Depth contours, shoreline configurations, and interactions with other currents influence a current's direction and strength. Puffins and guillemots also suffered from the collapse of the herring population, especially the puffins on the Lofoten Islands. Waves are formed when winds scrape across the ocean surface. Its properties also show significant annual fluctuations, with long-term average temperature being below 3C and salinity between 34.7 and 34.9. Within the atoll, paved walking paths exist from the village of La Gigi, which leads to a promontory from where scenic views of the large lagoon (during low tides) and the mangrove species are seen. Ans. [25] The atoll consists of reef limestone of Pleistocene age (with irregular coral formations called "champignon",[26] made up of two layers of varying stages of crystallization [27]) and this extends over an average width of 2 kilometres (1.2mi) rising to a height of 8 metres (26ft) above sea level, and forming the rim line (low cliffs with "deep notches, preceded by jagged pinnacles") of the shallow central lagoon. (iii) Ocean currents. Cats have been removed from all of the islands except Grande Terre Island, which allowed for the reintroduction of the Aldabra rail to Picard Island. As a result, the quality of water is deteriorating day by day. A single acre of seagrass can support upwards of 40,000 fish and 50 million small invertebrates, and there are often tens to hundreds more animals in a seagrass bed compared to adjacent bare sandy areas. [43], At the 500hPa level, the air temperature averages 7C (18F) within the tropics, but air in the tropics is normally dry at this height, giving the air room to wet-bulb, or cool as it moistens, to a more favorable temperature that can then support convection. The southern basin is larger and deeper, with large areas between 3,500 and 4,000 metres deep. They have no flowers or veins, and their holdfasts simply attach to the bottom and are generally not specialized to take in nutrients. Episodes of warm seawater temperatures can also damage seagrasses. [7] Many species of butterflies also flutter around Aldabra. (e) Tides are the rhythmic rise and fall of ocean water that occurs twice in a day. [9], Aldabra, along with Desroches and Farquhar, was part of the British Indian Ocean Territory from 1965 until Seychelles' independence in 1976. [18], El Nio is defined by prolonged differences in Pacific Ocean surface temperatures when compared with the average value. When El Nio conditions last for many months, extensive ocean warming and the reduction in Easterly Trade winds limits upwelling of cold nutrient-rich deep water and its economic impact to local fishing for an international market can be serious. The windward southern coast is made up of sand dunes.[7]. While the capelin benefited from the reduced fishing, the temperature rise in the 1980s and competition for food with the herring resulted in a near disappearance of young capelin from the Norwegian Sea. They contain almost 98 percent of all the water on Earth . The small vulnerable juveniles are prey to coconut crabs, land crabs, rats and birds. Sewerage water also gets mixed into these water bodies. For the cruise ship, see. Salle, A.B.A. The Chesapeake Bay (/ t s p i k / CHESS--peek) is the largest estuary in the United States. Warm current The Gulf Stream [4] However, the eastern Pacific Ocean, subtropical North Atlantic Ocean, and Southern Ocean have warmed more slowly than the global average or have experienced cooling since the 1950s. Name one warm current and one cold current. In nutrient poor regions, the seagrass plants themselves help nutrient cycling by taking up nutrients from the soil and releasing them into the water through their leaves, acting as a nutrient pump. Like other flowering plants, their roots can absorb nutrients. It is connected to the Langeled pipeline, currently the world's longest underwater pipeline, and thus to a major European gas pipeline network. 2. Onshore winds can cause a considerable warm-up even in areas where upwelling is fairly constant, such as the northwest coast of South America. [7] They are covered with a mixture of gravel, sand, and mud, and the trenches are used by fish as spawning grounds. Healthy plants are thought to be resistant to the disease, indicating importance of reducing other stressors like pollution. [35][36] Tortoise size varies substantially across the atoll, but adult tortoises typically have a carapace length of 105 centimetres (41in) and can weigh up to 350 kilograms (770lb). Ans. Q.5. The lagoon is encircled by fringing coral reef. They raise the water level close to the shores. It is a precious resource of nature. (h) Samantha mesmerised everybody with her magic tricks. The high tides also help in fishing. In the eastern zone of the lagoon, though the surface is continuous, sediment beds are also seen. Such deltas are characterized by a dendritic structure (branched, like a tree) due to newly-formed distributaries during times of high water. The Norwegian Sea is ice-free and provides a direct route from the Atlantic to the Russian ports in the Arctic (Murmansk, Arkhangelsk, and Kandalaksha), which are directly linked to central Russia. Climate and tides. (h) Thames, (i) yellow,(j) Conga. Oceans cover nearly 71 percent of Earths surface. [8] Submarine thresholds and continental slopes mark the borders of these basins with the adjacent seas. Green and F.T. Aldabra was designated as a site under the Indian Ocean South East Asia (IOSEA) turtle network, in their 2014 convention. (Hint: colour!) [7][26] This flora includes 19 endemic species and 22 species that are only common to neighboring islands, and several of these species are on the IUCN Red List. Seagrasses support commercial fisheries and biodiversity, clean the surrounding water and help take carbon dioxide out of the atmosphere. These distinct structures and growth forms affect how seagrasses influence their environment and what species live in the habitats they create. A two-roomed jail was also built in the village, a remnant of which is extant. 10. The accepted definition is a warming or cooling of at least 0.5C (0.9F) averaged over the east-central tropical Pacific Ocean. (d) Temperature, winds, the gravitational pull of the sun, the earth, and the moon; warm and cold currents are the factors that affect the movement of ocean water. Because the specific heat of ocean water is much larger than that of air, the top 2.5 m of the ocean holds as much heat as the entire atmosphere above it. ", National Centers for Environmental Prediction, "El Nio / Southern Oscillation (ENSO) June 2009", "Global Sea-Surface Temperature Distribution Determined From an Environmental Satellite", 10.1175/1520-0493(1972)100<0010:GSTDDF>2.3.CO;2, "Accuracy of in situ sea surface temperatures used to calibrate infrared satellite measurements", "Infrared and microwave remote sensing of sea surface temperature (SST)", University Corporation for Atmospheric Research, "Subject: A15) How do tropical cyclones form? Ans. Q.6. Warm sea surface temperatures are known to be a cause of tropical cyclogenesis over the Earth's oceans. NASA's (National Aeronautic and Space Administration) Moderate Resolution Imaging Spectroradiometer (MODIS) SST satellites have been providing global SST data since 2000, available with a one-day lag. Aldabra atoll is in the most southwesterly part of the Seychelles, and is closer to the coast of Africa 630km (390mi) than to Mah. Efforts made to grow plantation crops of coconuts, cotton, and sisal failed due to inadequate water sources on the atoll; relics of these plantations are still found on some of the islands. It is an artificial enclosure for keeping small house plants. [7] The temperature and salinity of this current show strong seasonal and annual fluctuations. The atmospheric mixed layer results from convective air motions, typically seen towards the middle of the day when air at the surface is warmed and rises. Tides may be high or low. (f)The tiffin box rolled down and all the food fell in dusty potholes. (a)(i), (b)(ii), (c)(i). The carbon stored in sediments from coastal ecosystems including seagrass meadows, mangrove forests and salt marshes is known as "blue carbon" because it is stored in the sea. The travel distance from Rotterdam to Tokyo is 21,100km (13,111mi) via the Suez Canal and only 14,100km (8,761mi) through the Norwegian Sea. [V. In addition, BLT is the key factor in establishing the mean state that is perturbed during El Nino/La Nia[15]. As of 2015, the seagrass Zostera marina has increased from these seeded plots to cover 6,195 acres. They contain salty water. The combined influence of temperature and salinity changes results in an abrupt density change, or pycnocline. It got submerged. The deepening of the mixed layer in the wintertime in the North Atlantic is therefore associated with a strong decrease in surface chlorophyll a. These external factors contribute to an impressive diversity of deltas around the world. Many people believe that the ancient Greek historian Herodotus first coined the term delta nearly 2,500 years ago as many deltas are shaped like the Greek delta () symbol. Tsunami is a Japanese word that means harbour waves as the harbours get destroyed whenever there is a tsunami. These westward currents are driven by downwelling Rossby waves and represent either a westward advection of BLT or a preferential deepening of the deeper thermocline versus the shallower halocline due to Rossby wave dynamics (i.e. In 2018, 41% of stocks were excessively harvested. Often, an abrupt temperature change called a thermocline occurs to mark the bottom of the mixed layer; sometimes there may be an abrupt salinity change called a halocline that occurs as well. By working together, these international science teams hope to not only understand how these critical coastal habitats work, but how to best protect them and ensure their existence in the future.
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