Sea surface microlayer

The sea surface microlayer (SML) is the top 1000 micrometers (or 1 millimeter) of the ocean surface. It is the boundary layer where all exchange occurs between the atmosphere and the ocean.[1] The chemical, physical, and biological properties of the SML differ greatly from the sub-surface water just a few centimeters beneath.[2]

Overview of Properties

Organic compounds such as amino acids, carbohydrates, fatty acids, and phenols are highly enriched in the SML interface. Most of these come from biota in the sub-surface waters, which decay and become transported to the surface,[3][4] though other sources exist also such as atmospheric deposition, coastal runoff, and anthropogenic nutrification.[1] The relative concentration of these compounds is dependent on the nutrient sources as well as climate conditions such as wind speed and precipitation.[4] These organic compounds on the surface create a "film," referred to as a "slick" when visible,[2] which affects the physical and optical properties of the interface. These films occur because of the hydrophobic tendencies of many organic compounds, which causes them to protrude into the air-interface.[1][5] The existence of organic surfactants on the ocean surface impedes wave formation for low wind speeds. For increasing concentrations of surfactant there is an increasing critical wind speed necessary to create ocean waves.[1][2] Increased levels of organic compounds at the surface also hinders air-sea gas exchange at low wind speeds.[6] One way in which particulates and organic compounds on the surface are transported into the atmosphere is the process called "bubble bursting".[1][7] Bubbles generate the major portion of marine aerosols.[6][8][9] They can be dispersed to heights of several meters, picking up whatever particles latch on to their surface. However, the major supplier of materials comes from the SML.[3]

Health and Environment

Extensive research has shown that the SML contains elevated concentration of bacteria, viruses, toxic metals and organic pollutants as compared to the sub-surface water.[1][10][11][12][13] These materials can be transferred from the sea-surface to the atmosphere in the form of wind-generated aqueous aerosols due to their high vapor tension and a process known as volatilisation.[7] When airborne, these microbes can be transported long distances to coastal regions. If they hit land they can have detrimental effects on animals, vegetation and human health.[14] Marine aerosols that contain viruses can travel hundreds of kilometers from their source and remain in liquid form as long as the humidity is high enough (over 70%).[15][16][17] These aerosols are able to remain suspended in the atmosphere for about 31 days.[3] Evidence suggests that bacteria can remain viable after being transported inland through aerosols. Some reached as far as 200 meters at 30 meters above sea level.[18] A month-long study done by scientists in the Tyrrhenian Sea in 1999 revealed that signals of pollution from chemicals of petrogenic origin in the harbor of Livorno was the result of chemicals found in the SML.[19] It was also noted that the process which transfers this material to the atmosphere causes further enrichment in both bacteria and viruses in comparison to either the SML or sub-surface waters (up to three orders of magnitude in some locations).[18]

Measurement

Devices used to sample the concentrations of particulates and compounds of the SML include a glass fabric, metal mesh screens, and other hydrophobic surfaces. These are placed on a rotating cylinder which collects surface samples as it rotates on top of the ocean surface.[20]

References

  1. ^ a b c d e f Liss, P.S., Duce, R.A., 1997. The Sea Surface and Global Change. Cambridge Univ. Press, Cambridge.
  2. ^ a b c Zhang, Zhengbin et al. (2003). Studies on the sea surface microlayer II. The layer of sudden change of physical and chemical properties. Journal of Colloid and Interface Science. 264, 148-159.
  3. ^ a b c Aller, J., Kuznetsova, M., Jahns, C., Kemp, P. (2005) The sea surface microlayer as a source of viral and bacterial enrichment in marine aerosols. Journal of aerosol science. Vol. 36, pp. 801-812.
  4. ^ a b Carlson, David J. (1983). Dissolved Organic Materials in Surface Microlayers: Temporal and Spatial Variability and Relation to Sea State. Limnology and Oceanography, 28.3. 415-431
  5. ^ Carlson, David J. (1982). Surface microlayer phenolic enrichments indicate sea surface slicks. Nature. 296.1. 426-429.
  6. ^ a b Woodcock, A. (1953). Salt nuclei in marine air as a function of altitude and wind force. Journal of Meteorology, 10, 362–371.
  7. ^ a b Wallace Jr., G.T., Duce, R.A., 1978. Transport of particulateorganic matter by bubbles in marine waters. Limnol. Oceanogr. 23 Ž6., 1155–1167.
  8. ^ Gustafsson, M. E. R., & Franzen, L. G. (2000). Inland transport of marine aerosols in southern Sweden. Atmospheric Environments, 34, 313–325.
  9. ^ Grammatika, M., & Zimmerman, W. B. (2001). Microhydrodynamics offloatation process in the sea surface layer. Dynamics of Atmospheres and Ocean, 34, 327–348.
  10. ^ Blanchard, D.C., 1983. The production, distribution and bacterial enrichment of the sea-salt aerosol. In: Liss, P.S., Slinn, W.G.N. ŽEds.., Air–Sea Exchange of Gases and Particles. D. Reidel Publishing Co., Dordrecht, Netherlands, pp. 407-444.
  11. ^ Hoffmann, G.L., Duce, R.A., Walsh, P.R., Hoffmann, E.J., Ray, B.J., 1974. Residence time of some particulate trace metals in the oceanic surface microlayer: significance of atmospheric deposition. J. Rech. Atmos. 8, 745–759.
  12. ^ Hunter, K.A., 1980. Process affecting particulate trace metals in the sea surface microlayer. Mar. Chem. 9, 49–70.
  13. ^ Hardy, J.T., Word, J., 1986. Contamination of the water surface of Puget Sound. Puget Sound Notes, U.S. EPA. Region 10 Seattle, WA, pp. 3–6.
  14. ^ WHO, 1998. Draft guidelines for safe recreational water environments: coastal and fresh waters, draft for consultation. World Health Organization, Geneva, EOSrDRAFTr98 14, pp. 207–299.
  15. ^ Klassen, R. D., & Roberge, P. R. (1999). Aerosol transport modeling as an aid to understanding atmospheric corrosivity patterns. Materials & Design, 20, 159–168.
  16. ^ Moorthy, K. K., Satheesh, S. K., & Krishna Murthy, B.V. (1998). Characteristics ofspectral optical depths and size distributions of aerosols over tropical oceanic regions. Journal of Atmospheric and Solar–Terrestrial Physics, 60, 981–992.
  17. ^ Chow, J. C., Watson, J. G., Green, M. C., Lowenthal, D. H., Bates, B., Oslund, W., & Torre, G. (2000). Cross-border transport and spatial variability of suspended particles in Mexicali and California’s Imperial Valley. Atmospheric Environment, 34, 1833–1843.
  18. ^ a b Marks, R., Kruczalak, K., Jankowska, K., & Michalska, M. (2001). Bacteria and fungi in air over the GulfofGdansk and Baltic sea. Journal of Aerosol Science, 32, 237–250.
  19. ^ Cincinelli A.; Stortini A.M.; Perugini M.; Checchini L.; Lepri L., 2001. Organic Pollutants in sea-surface microlayer and aerosol in the coastal environment Of Leghorn- (Tyrrhenian Sea). Marine Chemistry, Volume 76, Number 1, pp. 77-98(22)
  20. ^ Harvey, George W. (1966). Microlayer Collection from the Sea Surface: A New Method and Initial Results. Limnology and Oceanography, 11.4. 608-613
Bahama Banks

The Bahama Banks are the submerged carbonate platforms that make up much of the Bahama Archipelago. The term is usually applied in referring to either the Great Bahama Bank around Andros Island, or the Little Bahama Bank of Grand Bahama Island and Great Abaco, which are the largest of the platforms, and the Cay Sal Bank north of Cuba. The islands of these banks are politically part of the Bahamas. Other banks are the three banks of the Turks and Caicos Islands, namely the Caicos Bank of the Caicos Islands, the bank of the Turks Islands, and wholly submerged Mouchoir Bank. Further southeast are the equally wholly submerged Silver Bank and Navidad Bank north of the Dominican Republic.

Carbonate platform

A carbonate platform is a sedimentary body which possesses topographic relief, and is composed of autochthonic calcareous deposits. Platform growth is mediated by sessile organisms whose skeletons build up the reef or by organisms (usually microbes) which induce carbonate precipitation through their metabolism. Therefore, carbonate platforms can not grow up everywhere: they are not present in places where limiting factors to the life of reef-building organisms exist. Such limiting factors are, among others: light, water temperature, transparency and pH-Value. For example, carbonate sedimentation along the Atlantic South American coasts takes place everywhere but at the mouth of the Amazon River, because of the intense turbidity of the water there. Spectacular examples of present-day carbonate platforms are the Bahama Banks under which the platform is roughly 8 km thick, the Yucatan Peninsula which is up to 2 km thick, the Florida platform, the platform on which the Great Barrier Reef is growing, and the Maldive atolls. All these carbonate platforms and their associated reefs are confined to tropical latitudes. Today's reefs are built mainly by scleractinian corals, but in the distant past other organisms, like archaeocyatha (during the Cambrian) or extinct cnidaria (tabulata and rugosa) were important reef builders.

Keith Hunter (chemist)

Keith Andrew Hunter (24 November 1951 – 24 October 2018) was a New Zealand ocean chemist who was a professor of chemistry and pro-vice-chancellor of sciences, at the University of Otago.

List of submarine volcanoes

A list of active and extinct submarine volcanoes and seamounts located under the world's oceans. There are estimated to be 40,000 to 55,000 seamounts in the global oceans. Almost all are not well-mapped and many may not have been identified at all. Most are unnamed and unexplored. This list is therefore confined to seamounts that are notable enough to have been named and/or explored.

Ocean surface topography

Ocean surface topography or sea surface topography, also called ocean dynamic topography, are highs and lows on the ocean surface, similar to the hills and valleys of Earth's land surface depicted on a topographic map.

These variations are expressed in terms of average sea surface height (SSH) relative to the Earth's geoid.

The main purpose of measuring ocean surface topography is to understand the large-scale ocean circulation.

Oceanic plateau

An oceanic or submarine plateau is a large, relatively flat elevation that is higher than the surrounding relief with one or more relatively steep sides.There are 184 oceanic plateaus covering an area of 18,486,600 km2 (7,137,700 sq mi), or about 5.11% of the oceans. The South Pacific region around Australia and New Zealand contains the greatest number of oceanic plateaus (see map).

Oceanic plateaus produced by large igneous provinces are often associated with hotspots, mantle plumes, and volcanic islands — such as Iceland, Hawaii, Cape Verde, and Kerguelen. The three largest plateaus, the Caribbean, Ontong Java, and Mid-Pacific Mountains, are located on thermal swells. Other oceanic plateaus, however, are made of rifted continental crust, for example Falkland Plateau, Lord Howe Rise, and parts of Kerguelen, Seychelles, and Arctic ridges.

Plateaus formed by large igneous provinces were formed by the equivalent of continental flood basalts such as the Deccan Traps in India and the Snake River Plain in the United States.

In contrast to continental flood basalts, most igneous oceanic plateaus erupt through young and thin (6–7 km (3.7–4.3 mi)) mafic or ultra-mafic crust and are therefore uncontaminated by felsic crust and representative for their mantle sources.

These plateaus often rise 2–3 km (1.2–1.9 mi) above the surrounding ocean floor and are more buoyant than oceanic crust. They therefore tend to withstand subduction, more-so when thick and when reaching subduction zones shortly after their formations. As a consequence, they tend to "dock" to continental margins and be preserved as accreted terranes. Such terranes are often better preserved than the exposed parts of continental flood basalts and are therefore a better record of large-scale volcanic eruptions throughout Earth's history. This "docking" also means that oceanic plateaus are important contributors to the growth of continental crust. Their formations often had a dramatic impact on global climate, such as the most recent plateaus formed, the three, large, Cretaceous oceanic plateaus in the Pacific and Indian Ocean: Ontong Java, Kerguelen, and Caribbean.

Outline of oceanography

The following outline is provided as an overview of and introduction to Oceanography.

Physical oceanography

Physical oceanography is the study of physical conditions and physical processes within the ocean, especially the motions and physical properties of ocean waters.

Physical oceanography is one of several sub-domains into which oceanography is divided. Others include biological, chemical and geological oceanography.

Physical oceanography may be subdivided into descriptive and dynamical physical oceanography.Descriptive physical oceanography seeks to research the ocean through observations and complex numerical models, which describe the fluid motions as precisely as possible.

Dynamical physical oceanography focuses primarily upon the processes that govern the motion of fluids with emphasis upon theoretical research and numerical models. These are part of the large field of Geophysical Fluid Dynamics (GFD) that is shared together with meteorology. GFD is a sub field of Fluid dynamics describing flows occurring on spatial and temporal scales that are greatly influenced by the Coriolis force.

Sea foam

Sea foam, ocean foam, beach foam, or spume is a type of foam created by the agitation of seawater, particularly when it contains higher concentrations of dissolved organic matter (including proteins, lignins, and lipids) derived from sources such as the offshore breakdown of algal blooms. These compounds can act as surfactants or foaming agents. As the seawater is churned by breaking waves in the surf zone adjacent to the shore, the surfactants under these turbulent conditions trap air, forming persistent bubbles that stick to each other through surface tension. Sea foam is a global phenomenon and it varies depending on location and the potential influence of the surrounding marine, freshwater, and/or terrestrial environments. Due to its low density and persistence, foam can be blown by strong on-shore winds from the beach face inland.

Undersea mountain range

Undersea mountain ranges are mountain ranges that are mostly or entirely underwater, and specifically under the surface of an ocean. If originated from current tectonic forces, they are often referred to as a mid-ocean ridge. In contrast, if formed by past above-water volcanism, they are known as a seamount chain. The largest and best known undersea mountain range is a mid-ocean ridge, the Mid-Atlantic Ridge. It has been observed that, "similar to those on land, the undersea mountain ranges are the loci of frequent volcanic and earthquake activity".

Wave base

The wave base, in physical oceanography, is the maximum depth at which a water wave's passage causes significant water motion. For water depths deeper than the wave base, bottom sediments and the seafloor are no longer stirred by the wave motion above.

Waves
Circulation
Tides
Landforms
Plate
tectonics
Ocean zones
Sea level
Acoustics
Satellites
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