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Topic Review
Threats to Sustainability
Plastics are a precious, versatile set of materials. The accumulation of plastic waste threatens the environment. Recycling plastic waste can produce many new products. The many opportunities for using plastic waste create pressure for a strategy to develop or improve current waste management systems to reduce the negative impact on humans, fauna and flora.
  • 3.3K
  • 13 Dec 2022
Topic Review
Atmospheric Correction for Landsat 8
Ocean colour (OC) remote sensing is important for monitoring marine ecosystems. However, inverting the OC signal from the top-of-atmosphere (TOA) radiance measured by satellite sensors remains a challenge as the retrieval accuracy is highly dependent on the performance of the atmospheric correction as well as sensor calibration. In this study, the performances of four atmospheric correction (AC) algorithms, the Atmospheric and Radiometric Correction of Satellite Imagery (ARCSI), Atmospheric Correction for OLI ‘lite’ (ACOLITE), Landsat 8 Surface Reflectance (LSR) Climate Data Record (Landsat CDR), herein referred to as LaSRC (Landsat 8 Surface Reflectance Code), and the Sea-Viewing Wide Field-of-View Sensor (SeaWiFS) Data Analysis System (SeaDAS), implemented for Landsat 8 Operational Land Imager (OLI) data, were evaluated. The OLI-derived remote sensing reflectance (Rrs) products (also known as Level-2 products) were tested against near-simultaneous in-situ data acquired from the OC component of the Aerosol Robotic Network (AERONET-OC). Analyses of the match-ups revealed that generic atmospheric correction methods (i.e., ARCSI and LaSRC), which perform reasonably well over land, provide inaccurate Level-2 products over coastal waters, in particular, in the blue bands. Between water-specific AC methods (i.e., SeaDAS and ACOLITE), SeaDAS was found to perform better over complex waters with root-mean-square error (RMSE) varying from 0.0013 to 0.0005 sr−1 for the 443 and 655 nm channels, respectively. An assessment of the effects of dominant environmental variables revealed AC retrieval errors were influenced by the solar zenith angle and wind speed for ACOLITE and SeaDAS in the 443 and 482 nm channels. Recognizing that the AERONET-OC sites are not representative of inland waters, extensive research and analyses are required to further evaluate the performance of various AC methods for high-resolution imagers like Landsat 8 and Sentinel-2 under a broad range of aquatic/atmospheric conditions.
  • 3.3K
  • 30 Oct 2020
Topic Review
Younger Dryas
The Younger Dryas (around 12,900 to 11,700 years BP) was a return to glacial conditions after the Late Glacial Interstadial, which temporarily reversed the gradual climatic warming after the Last Glacial Maximum (LGM) started receding around 20,000 BP. It is named after an indicator genus, the alpine-tundra wildflower Dryas octopetala, as its leaves are occasionally abundant in late glacial, often minerogenic-rich sediments, such as the lake sediments of Scandinavia. Physical evidence of a sharp decline in temperature over most of the Northern Hemisphere has been discovered by geological research. This temperature change occurred at the end of what the earth sciences refer to as the Pleistocene epoch and immediately before the current, warmer Holocene epoch. In archaeology, this time frame coincides with the final stages of the Upper Paleolithic in many areas. The Younger Dryas was the most recent and longest of several interruptions to the gradual warming of the Earth's climate since the severe LGM, about 27,000 to 24,000 years BP. The change was relatively sudden, taking place in decades, and it resulted in a decline of temperatures in Greenland by 4 to 10°C (7.2 to 18°F) and advances of glaciers and drier conditions, over much of the temperate Northern Hemisphere. It is thought to have been caused by a decline in the strength of the Atlantic meridional overturning circulation, which transports warm water from the Equator towards the North Pole, in turn thought to have been caused by an influx of fresh, cold water from North America to the Atlantic. The Younger Dryas was a period of climatic change, but the effects were complex and variable. In the Southern Hemisphere and some areas of the Northern Hemisphere, such as southeastern North America, a slight warming occurred.
  • 3.3K
  • 14 Oct 2022
Topic Review
Landsat 8 and Landsat 9
With the launch of Landsat 9 in September 2021, an optimal opportunity for in-flight cross-calibration occurred when Landsat 9 flew underneath Landsat 8 while being moved into its final orbit. Since the two instruments host nearly identical imaging systems, the underfly event offered ideal cross-calibration conditions. Using the underfly imagery collected by the instruments to estimate cross-calibration parameters for Landsat 9 for a calibration update scheduled at the end of the on-orbit initial verification (OIV) period was studied. Three types of uncertainty were considered: geometric, spectral, and angular (bidirectional reflectance distribution function—BRDF). Differences caused by geometric uncertainty were found to be negligible for this application. 
  • 3.2K
  • 01 Jun 2022
Topic Review
Kiev
Kiev or Kyiv (Ukrainian: Київ; Russian: Киев, romanized: Kiyev) is the capital and most populous city of Ukraine . It is in north-central Ukraine along the Dnieper River. Its population in July 2015 was 2,887,974 (though higher estimated numbers have been cited in the press), making Kiev the seventh-most populous city in Europe. Kiev is an important industrial, scientific, educational and cultural center of Eastern Europe. It is home to many high-tech industries, higher education institutions, and historical landmarks. The city has an extensive system of public transport and infrastructure, including the Kiev Metro. The city's name is said to derive from the name of Kyi, one of its four legendary founders. During its history, Kiev, one of the oldest cities in Eastern Europe, passed through several stages of prominence and obscurity. The city probably existed as a commercial center as early as the 5th century. A Slavic settlement on the great trade route between Scandinavia and Constantinople, Kiev was a tributary of the Khazars, until its capture by the Varangians (Vikings) in the mid-9th century. Under Varangian rule, the city became a capital of the Kievan Rus', the first East Slavic state. Completely destroyed during the Mongol invasions in 1240, the city lost most of its influence for the centuries to come. It was a provincial capital of marginal importance in the outskirts of the territories controlled by its powerful neighbours, first Lithuania, then Poland and Russia. The city prospered again during the Russian Empire's Industrial Revolution in the late 19th century. In 1918, after the Ukrainian National Republic declared independence from Soviet Russia, Kiev became its capital. From 1921 onwards Kiev was a city of Soviet Ukraine, which was proclaimed by the Red Army, and, from 1934, Kiev was its capital. The city was almost completely ruined during World War II but quickly recovered in the postwar years, remaining the Soviet Union's third-largest city. Following the collapse of the Soviet Union and Ukrainian independence in 1991, Kiev remained Ukraine's capital and experienced a steady influx of ethnic Ukrainian migrants from other regions of the country. During the country's transformation to a market economy and electoral democracy, Kiev has continued to be Ukraine's largest and wealthiest city. Its armament-dependent industrial output fell after the Soviet collapse, adversely affecting science and technology, but new sectors of the economy such as services and finance facilitated Kiev's growth in salaries and investment, as well as providing continuous funding for the development of housing and urban infrastructure. Kiev emerged as the most pro-Western region of Ukraine; parties advocating tighter integration with the European Union dominate during elections.
  • 3.2K
  • 10 Nov 2022
Topic Review
Floating Island
A floating island is a mass of floating aquatic plants, mud, and peat ranging in thickness from several centimeters to a few meters. Floating islands are a common natural phenomenon that are found in many parts of the world. They exist less commonly as an artificial phenomenon. Floating islands are generally found on marshlands, lakes, and similar wetland locations, and can be many hectares in size.
  • 3.2K
  • 21 Oct 2022
Topic Review
List of Research Stations in the Arctic
A number of governments maintain permanent research stations in the Arctic. Also known as Arctic bases, polar stations or ice stations, these bases are widely distributed across the northern polar region of the earth. Historically few research stations have been permanent. Most of them were temporary, being abandoned after the completion of the project or owing to lack of funding to continue the research. Some of these were military or intelligence stations (listening posts) created as a result of the proximity of the U.S. and Soviet Union to each other's landmass across the polar region. Ice stations are constructed on land or on ice that rests on land, while others are drifting ice stations built on the sea ice of the high latitudes of the Arctic Ocean.
  • 3.2K
  • 30 Nov 2022
Topic Review
Carbon Cycling in Mangrove Ecosystems
The carbon cycle in mangrove ecosystems is an important biogeochemical pathway in understanding the links between this forest ecosystem and both the atmosphere and the adjacent coastal ocean. Mangroves are a major habitat in the coastal zone for storing carbon in the soils of their deep forest floor, and for exporting to adjacent coastal seas significant quantities of dissolved inorganic carbon (DIC). The large export of DIC is sufficient to result in adjacent coastal waters becoming a source of carbon dioxide to the atmosphere in tropical and subtropical latitudes.
  • 3.2K
  • 21 Sep 2020
Topic Review
Artificial Island Developments
Artificial island development (AID) to tackle rampant urbanization on scarce land puts all marine biodiversity at huge risk and is recognized as a global conservation issue worldwide.
  • 3.2K
  • 16 May 2022
Topic Review
Bioremediation Techniques
Bioremediation is a process that uses biological organisms to remove or re-treat an environmental pollutant through metabolic processes and plants to eradicate hazardous pollutants and restore the ecosystem to its original condition.
  • 3.2K
  • 24 Apr 2023
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