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'''Paleosalinity''' (or Palaeosalinity) is the salinity of the global ocean or of an [[ocean basin]] at a point in geological history. | |||
== Importance == | |||
From [[Bjerrum plot]]s, it is found that a decrease in the salinity of an aqueous fluid will act to increase the value of the carbon dioxide-carbonate system equilibrium constants, (pK*). This means that the relative proportion of [[carbonate]] with respect to carbon dioxide is higher in more salinity fluids, e.g. [[seawater]], than in fresher waters. Of crucial importance for [[paleoclimatology]] is the observation that an increase in [[salinity]] will thus reduce the [[solubility]] of carbon dioxide in the oceans. Since there is thought to have been a 120m depression in sea level at the last glacial maximum due to the extensive formation of [[ice sheet]]s (which are solely freshwater), this represents a significant fractionation towards saltier seas during glacial periods. Correspondingly, this will cause a net outgassing of carbon dioxide into the atmosphere because of its reduced solubility, acting to increase atmospheric carbon dioxide by 6.5[[permille|‰]]. This is thought to partly offset the net decrease of 80-100‰ observed during glacial periods.<ref>{{cite journal | title = Glacial/interglacial variations in Carbon Dioxide | journal = Nature | first = D.M. | last = Sigman | coauthors = E.A. Boyle | volume = 407| id = | url = http://www.up.ethz.ch/education/biogeochem_cycles/reading_list/sigman_nat_00.pdf | format = PDF | accessdate = 2010-05-17 | pmid=11057657 | doi=10.1038/35038000 | year = 2000 | issue = 6806 | pages = 859–869}}</ref> | |||
=== Stratification === | |||
In addition, it is thought that extensive salinity stratification can lead to a reduction in the [[meridional overturning circulation]] (MOC) through the slowing of thermohaline circulation. Increased stratification means that there is effectively a barrier to subduction of parcels of water; [[isopycnal]]s effectively do no outcrop at the surface and are parallel to the surface. The ocean, in this case, can be described as "less ventilated", and this has been implicated in the slowing down of the MOC. | |||
== Measuring Paleosalinity == | |||
There may exist proxies for salinity, but to date the main way that salinity has been measured has been by directly measuring [[chlorinity]] in [[pore fluid]]s.<ref>{{cite journal | doi = 10.1126/science.1076252 | title = The Salinity, Temperature, and delta 18O of the Glacial Deep Ocean | journal = Science | first = J.F. | last = Adkins | coauthors = McIntyre, K. and Schrag, D.P. | volume = 298 | issue = 5599 | pages = 1769–73 | year = 2002 | pmid = 12459585| id = | url = http://schraglab.unix.fas.harvard.edu/publications/CV49.pdf | format = PDF | accessdate = 2010-05-17 | bibcode=2002Sci...298.1769A}}</ref> Adkins et al. (2002) used pore fluid chlorinity in [[Ocean Drilling Program|ODP]] cores, with the paleo-depth estimated from nearby coral horizons. Chlorinity was measured rather than pure salinity because the major ions in seawater are not constant with depth in the sediment column; for example, sulphate reduction and cation-clay interactions can change overall salinity, whereas chlorinity is not heavily affected. | |||
== Paleosalinity during the Last Glacial Maximum == | |||
Adkins' study found that global salinity increased with a global sea level drop of 120m. Analyzing <sup>18</sup>O data they also found that deep waters were within error of the freezing point, with oceanic waters exhibiting a greater degree of homogeneity in temperatures. In contrast, variations in salinity were much greater than they are today. Modern day salinities are all within 0.5 [[Practical salinity unit|psu]] of the global average salinity of 34.7 psu, whereas salinities during the last glacial maximum (LGM) ranged from 35.8 psu in the North Atlantic to 37.1 in the Southern Ocean. | |||
There are some notable differences in the hydrography at the LGM and present day. Today the North Atlantic Deep Water ([[NADW]]) is observed to be more saline than Antarctic Bottom Water ([[AABW]]), whereas at the last glacial maximum it was observed that the AABW was in fact more saline; a complete reversal. Today the NADW is more salty because of the Gulf Stream; this could thus indicate a reduction of flow through the Florida Straits due to lowered sea level. | |||
Another observation is that the Southern Ocean was vastly more salty at the LGM than today, and noticeably more salty. This is particularly intriguiging given the assumed importance of the [[Southern Ocean]] in oceanic dynamical regulation of ice ages. The extreme value of 37.1 psu is assumed to be a consequence of an increased degree of sea ice formation and export. This would account for the increased salinity, but would also account for the lack of oxygen isotopic fractionation; [[brine]] rejection without oxygen isotopic fractionation is thought to be highly characteristic of sea ice formation. | |||
=== The increased role of salinity === | |||
The presence of waters near the freezing point alters the balance of the relative effects of contrasts in salinity and temperature on sea water density. This is described in the equation, | |||
:<math>\frac{\Delta\rho}{\rho}=\alpha\Delta T-\beta\Delta S</math> | |||
where <math>\alpha</math> is the [[thermal expansion coefficient]] and <math>\beta</math> is the [[haline contraction coefficient]]. In particular, the ratio <math>\frac{\beta}{\alpha}</math> is crucial. Using the observed temperatures and salinities, in the modern ocean, <math>\frac{\beta}{\alpha}</math> is about 10 whilst at the LGM <math>\frac{\beta}{\alpha}</math> it is estimated to have been closer to 25. The modern [[thermohaline circulation]] is thus more controlled by density contrasts due to thermal differences, whereas during the LGM the oceans were more than twice as sensitive to differences in salinity rather than temperature. In this way, the thermohaline circulation can be considered to have been less "thermo" and more "haline". | |||
== See also == | |||
* [[Fresh water]] | |||
* [[Seawater]] | |||
* [[Thermohaline circulation]] | |||
== References == | |||
{{reflist}} | |||
== External links == | |||
*[http://www.salinometry.com/salinity-history History of salinity.] | |||
[[Category:Chemical oceanography]] | |||
[[Category:Aquatic ecology]] | |||
[[Category:Oceanography]] | |||
[[Category:Coastal geography]] | |||
Revision as of 12:38, 11 September 2013
Paleosalinity (or Palaeosalinity) is the salinity of the global ocean or of an ocean basin at a point in geological history.
Importance
From Bjerrum plots, it is found that a decrease in the salinity of an aqueous fluid will act to increase the value of the carbon dioxide-carbonate system equilibrium constants, (pK*). This means that the relative proportion of carbonate with respect to carbon dioxide is higher in more salinity fluids, e.g. seawater, than in fresher waters. Of crucial importance for paleoclimatology is the observation that an increase in salinity will thus reduce the solubility of carbon dioxide in the oceans. Since there is thought to have been a 120m depression in sea level at the last glacial maximum due to the extensive formation of ice sheets (which are solely freshwater), this represents a significant fractionation towards saltier seas during glacial periods. Correspondingly, this will cause a net outgassing of carbon dioxide into the atmosphere because of its reduced solubility, acting to increase atmospheric carbon dioxide by 6.5‰. This is thought to partly offset the net decrease of 80-100‰ observed during glacial periods.[1]
Stratification
In addition, it is thought that extensive salinity stratification can lead to a reduction in the meridional overturning circulation (MOC) through the slowing of thermohaline circulation. Increased stratification means that there is effectively a barrier to subduction of parcels of water; isopycnals effectively do no outcrop at the surface and are parallel to the surface. The ocean, in this case, can be described as "less ventilated", and this has been implicated in the slowing down of the MOC.
Measuring Paleosalinity
There may exist proxies for salinity, but to date the main way that salinity has been measured has been by directly measuring chlorinity in pore fluids.[2] Adkins et al. (2002) used pore fluid chlorinity in ODP cores, with the paleo-depth estimated from nearby coral horizons. Chlorinity was measured rather than pure salinity because the major ions in seawater are not constant with depth in the sediment column; for example, sulphate reduction and cation-clay interactions can change overall salinity, whereas chlorinity is not heavily affected.
Paleosalinity during the Last Glacial Maximum
Adkins' study found that global salinity increased with a global sea level drop of 120m. Analyzing 18O data they also found that deep waters were within error of the freezing point, with oceanic waters exhibiting a greater degree of homogeneity in temperatures. In contrast, variations in salinity were much greater than they are today. Modern day salinities are all within 0.5 psu of the global average salinity of 34.7 psu, whereas salinities during the last glacial maximum (LGM) ranged from 35.8 psu in the North Atlantic to 37.1 in the Southern Ocean.
There are some notable differences in the hydrography at the LGM and present day. Today the North Atlantic Deep Water (NADW) is observed to be more saline than Antarctic Bottom Water (AABW), whereas at the last glacial maximum it was observed that the AABW was in fact more saline; a complete reversal. Today the NADW is more salty because of the Gulf Stream; this could thus indicate a reduction of flow through the Florida Straits due to lowered sea level.
Another observation is that the Southern Ocean was vastly more salty at the LGM than today, and noticeably more salty. This is particularly intriguiging given the assumed importance of the Southern Ocean in oceanic dynamical regulation of ice ages. The extreme value of 37.1 psu is assumed to be a consequence of an increased degree of sea ice formation and export. This would account for the increased salinity, but would also account for the lack of oxygen isotopic fractionation; brine rejection without oxygen isotopic fractionation is thought to be highly characteristic of sea ice formation.
The increased role of salinity
The presence of waters near the freezing point alters the balance of the relative effects of contrasts in salinity and temperature on sea water density. This is described in the equation,
where is the thermal expansion coefficient and is the haline contraction coefficient. In particular, the ratio is crucial. Using the observed temperatures and salinities, in the modern ocean, is about 10 whilst at the LGM it is estimated to have been closer to 25. The modern thermohaline circulation is thus more controlled by density contrasts due to thermal differences, whereas during the LGM the oceans were more than twice as sensitive to differences in salinity rather than temperature. In this way, the thermohaline circulation can be considered to have been less "thermo" and more "haline".
See also
References
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The data offered is for normal info purposes only and isn't supposed to be personalised investment or monetary advice. Motley Fool Singapore contributor Stanley Lim would not personal shares in any corporations talked about. Singapore private home costs increased by 1.eight% within the fourth quarter of 2012, up from 0.6% within the earlier quarter. Resale prices of government-built HDB residences which are usually bought by Singaporeans, elevated by 2.5%, quarter on quarter, the quickest acquire in five quarters. And industrial property, prices are actually double the levels of three years ago. No withholding tax in the event you sell your property. All your local information regarding vital HDB policies, condominium launches, land growth, commercial property and more
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In its statement, the singapore property listing - website link, government claimed that the majority citizens buying their first residence won't be hurt by the new measures. Some concessions can even be prolonged to chose teams of consumers, similar to married couples with a minimum of one Singaporean partner who are purchasing their second property so long as they intend to promote their first residential property. Lower the LTV limit on housing loans granted by monetary establishments regulated by MAS from 70% to 60% for property purchasers who are individuals with a number of outstanding housing loans on the time of the brand new housing purchase. Singapore Property Measures - 30 August 2010 The most popular seek for the number of bedrooms in Singapore is 4, followed by 2 and three. Lush Acres EC @ Sengkang
Discover out more about real estate funding in the area, together with info on international funding incentives and property possession. Many Singaporeans have been investing in property across the causeway in recent years, attracted by comparatively low prices. However, those who need to exit their investments quickly are likely to face significant challenges when trying to sell their property – and could finally be stuck with a property they can't sell. Career improvement programmes, in-house valuation, auctions and administrative help, venture advertising and marketing, skilled talks and traisning are continuously planned for the sales associates to help them obtain better outcomes for his or her shoppers while at Knight Frank Singapore. No change Present Rules
Extending the tax exemption would help. The exemption, which may be as a lot as $2 million per family, covers individuals who negotiate a principal reduction on their existing mortgage, sell their house short (i.e., for lower than the excellent loans), or take part in a foreclosure course of. An extension of theexemption would seem like a common-sense means to assist stabilize the housing market, but the political turmoil around the fiscal-cliff negotiations means widespread sense could not win out. Home Minority Chief Nancy Pelosi (D-Calif.) believes that the mortgage relief provision will be on the table during the grand-cut price talks, in response to communications director Nadeam Elshami. Buying or promoting of blue mild bulbs is unlawful.
A vendor's stamp duty has been launched on industrial property for the primary time, at rates ranging from 5 per cent to 15 per cent. The Authorities might be trying to reassure the market that they aren't in opposition to foreigners and PRs investing in Singapore's property market. They imposed these measures because of extenuating components available in the market." The sale of new dual-key EC models will even be restricted to multi-generational households only. The models have two separate entrances, permitting grandparents, for example, to dwell separately. The vendor's stamp obligation takes effect right this moment and applies to industrial property and plots which might be offered inside three years of the date of buy. JLL named Best Performing Property Brand for second year running
The data offered is for normal info purposes only and isn't supposed to be personalised investment or monetary advice. Motley Fool Singapore contributor Stanley Lim would not personal shares in any corporations talked about. Singapore private home costs increased by 1.eight% within the fourth quarter of 2012, up from 0.6% within the earlier quarter. Resale prices of government-built HDB residences which are usually bought by Singaporeans, elevated by 2.5%, quarter on quarter, the quickest acquire in five quarters. And industrial property, prices are actually double the levels of three years ago. No withholding tax in the event you sell your property. All your local information regarding vital HDB policies, condominium launches, land growth, commercial property and more
There are various methods to go about discovering the precise property. Some local newspapers (together with the Straits Instances ) have categorised property sections and many local property brokers have websites. Now there are some specifics to consider when buying a 'new launch' rental. Intended use of the unit Every sale begins with 10 p.c low cost for finish of season sale; changes to 20 % discount storewide; follows by additional reduction of fiftyand ends with last discount of 70 % or extra. Typically there is even a warehouse sale or transferring out sale with huge mark-down of costs for stock clearance. Deborah Regulation from Expat Realtor shares her property market update, plus prime rental residences and houses at the moment available to lease Esparina EC @ Sengkang