Editing Oceanography (section)

==Branches==
[[File:Antarctic frontal-system hg.png|thumb|Oceanographic frontal systems on the [[Southern Hemisphere]]]]
[[File:Rosenstiel Applied Marine Physics Building.jpg|thumb|The Applied Marine Physics Building at the [[University of Miami]]'s [[Rosenstiel School of Marine, Atmospheric, and Earth Science]] on [[Virginia Key]], in September 2007]]
The study of oceanography is divided into these five branches:

===Biological oceanography===
{{Main|Biological oceanography}}
{{see also|Marine biology}}

Biological oceanography investigates the ecology and biology of marine organisms in the context of the physical, chemical and geological characteristics of their ocean environment.

===Chemical oceanography===
{{Main|Chemical oceanography}}
Chemical oceanography is the study of the [[chemistry]] of the ocean. Whereas chemical oceanography is primarily occupied with the study and understanding of seawater properties and its changes, [[ocean chemistry]] focuses primarily on the [[geochemical cycle]]s. The following is a central topic investigated by chemical oceanography.

====Ocean acidification====
{{Main|Ocean acidification}}
Ocean acidification describes the decrease in ocean [[PH#Seawater|pH]] that is caused by [[human impact on the environment|anthropogenic]] [[carbon dioxide]] ({{CO2}}) emissions into the [[Earth's atmosphere|atmosphere]].<ref name="cald03">{{Cite journal|last=Caldeira|first=K.|author2=Wickett, M. E.|date=2003|title=Anthropogenic carbon and ocean pH|url=http://pangea.stanford.edu/research/Oceans/GES205/Caldeira_Science_Anthropogenic%20Carbon%20and%20ocean%20pH.pdf |archive-url=https://web.archive.org/web/20070604185633/http://pangea.stanford.edu/research/Oceans/GES205/Caldeira_Science_Anthropogenic%20Carbon%20and%20ocean%20pH.pdf |archive-date=2007-06-04 |url-status=live|journal=[[Nature (journal)|Nature]]|volume=425|issue=6956|pages=OS11C–0385|doi=10.1038/425365a|pmid=14508477|bibcode=2001AGUFMOS11C0385C|s2cid=4417880}}</ref> Seawater is slightly [[alkalinity|alkaline]] and had a preindustrial [[pH]] of about 8.2. More recently, anthropogenic activities have steadily increased the [[carbon dioxide]] content of the atmosphere; about 30–40% of the added CO<sub>2</sub> is absorbed by the oceans, forming [[carbonic acid]] and lowering the pH (now below 8.1<ref name="EPA_Ocean_Acidity">{{cite web|title=Ocean Acidity|publisher=[[EPA]]|date=13 September 2013|url=http://www.epa.gov/climatechange/science/indicators/oceans/acidity.html|access-date=1 November 2013}}</ref>) through ocean acidification.<ref name="Feely04">{{cite journal|last=Feely|first=R. A.|display-authors=etal|title=Impact of Anthropogenic CO<sub>2</sub> on the CaCO<sub>3</sub> System in the Oceans|journal=Science|volume=305|date=July 2004|pages=362–366|bibcode=2004Sci...305..362F|doi=10.1126/science.1097329 |pmid=15256664|issue=5682|s2cid=31054160}}</ref><ref name="Zeebe2008">{{cite journal|last1=Zeebe|first1=R. E.|last2=Zachos|first2=J. C.|last3=Caldeira|first3=K.|last4=Tyrrell|first4=T.|title=OCEANS: Carbon Emissions and Acidification|journal=Science|volume=321|issue=5885|date=4 July 2008|pages=51–52|doi=10.1126/science.1159124|pmid=18599765|s2cid=206513402}}</ref><ref name="GattusoHansson2011">{{cite book|author1=Gattuso, J.-P.|author2=Hansson, L.|title=Ocean Acidification|url=https://books.google.com/books?id=8yjNFxkALjIC|date=15 September 2011|publisher=[[Oxford University Press]]|isbn=978-0-19-959109-1|oclc=730413873}}</ref> The pH is expected to reach 7.7 by the year 2100.<ref name="AboutAntarctica"/>

An important element for the [[skeleton]]s of marine animals is [[calcium]], but [[calcium carbonate]] becomes more soluble with pressure, so carbonate shells and skeletons dissolve below the [[carbonate compensation depth]].<ref name="Pinet">{{cite book|last=Pinet|first=Paul R.|date=1996|title=Invitation to Oceanography|pages=126, 134–135|publisher=[[West Publishing Company]]|url=https://books.google.com/books?id=eAqQvGYap24C|isbn=978-0-314-06339-7}}</ref> Calcium carbonate becomes more soluble at lower pH, so ocean acidification is likely to affect marine organisms with calcareous shells, such as oysters, clams, sea urchins and corals,<ref name="PMEL">{{cite web|url=http://www.pmel.noaa.gov/co2/story/What+is+Ocean+Acidification%3F|title=What is Ocean Acidification?|publisher=NOAA PMEL Carbon Program|access-date=15 September 2013|archive-date=2 September 2013|archive-url=https://web.archive.org/web/20130902071022/http://www.pmel.noaa.gov/co2/story/What+is+Ocean+Acidification%3F|url-status=dead}}</ref><ref name="orr05">{{Cite journal|last=Orr|first=James C.|display-authors=etal|date=2005|title=Anthropogenic ocean acidification over the twenty-first century and its impact on calcifying organisms|url=http://www.ipsl.jussieu.fr/~jomce/acidification/paper/Orr_OnlineNature04095.pdf|archive-url=https://web.archive.org/web/20080625100559/http://www.ipsl.jussieu.fr/~jomce/acidification/paper/Orr_OnlineNature04095.pdf|archive-date=25 June 2008|journal=Nature|volume=437|issue=7059|pages=681–686|doi=10.1038/nature04095|pmid=16193043|bibcode=2005Natur.437..681O|s2cid=4306199}}</ref> and the carbonate compensation depth will rise closer to the sea surface. Affected [[plankton]]ic organisms will include [[pteropod]]s, [[coccolithophorid]]s and [[foraminifera]], all important in the [[food chain]]. In tropical regions, [[coral]]s are likely to be severely affected as they become less able to build their calcium carbonate skeletons,<ref name="Cohen2009">{{cite journal|last1=Cohen|first1=A.|last2=Holcomb|first2=M.|date=2009|title=Why Corals Care About Ocean Acidification: Uncovering the Mechanism|journal=Oceanography|volume=24|pages=118–127|doi=10.5670/oceanog.2009.102|issue=4|hdl=1912/3179|doi-access=free|bibcode=2009Ocgpy..22d.118C |hdl-access=free}}</ref> in turn adversely impacting other [[Coral reef|reef]] dwellers.<ref name="AboutAntarctica">{{cite web|url=http://www.antarctica.gov.au/about-antarctica/environment/climate-change/ocean-acidification-and-the-southern-ocean|title=Ocean acidification|date=28 September 2007|publisher=Department of Sustainability, Environment, Water, Population & Communities: Australian Antarctic Division |access-date=17 April 2013}}</ref>

The current rate of ocean chemistry change seems to be unprecedented in Earth's geological history, making it unclear how well marine ecosystems will adapt to the shifting conditions of the near future.<ref name="Hönisch2012">{{cite journal |last1=Hönisch |first1=Bärbel |author-link=Bärbel Hönisch |last2=Ridgwell |first2=Andy |last3=Schmidt |first3=Daniela N. |last4=Thomas |first4=E. |last5=Gibbs |first5=S. J. |last6=Sluijs |first6=A. |last7=Zeebe |first7=R. |last8=Kump |first8=L. |last9=Martindale |first9=R. C. |last10=Greene |first10=S. E. |last11=Kiessling |first11=W. |display-authors=4 |date=2012 |title=The Geological Record of Ocean Acidification |journal=[[Science (journal)|Science]] |volume=335 |issue=6072 |pages=1058–1063 |bibcode=2012Sci...335.1058H |doi=10.1126/science.1208277 |pmid=22383840 |last12=Ries |first12=J. |last13=Zachos |first13=J. C. |last14=Royer |first14=D. L. |last15=Barker |first15=S. |last16=Marchitto |first16=T. M. |last17=Moyer |first17=R. |last18=Pelejero |first18=C. |last19=Ziveri |first19=P. |last20=Foster |first20=G. L. |last21=Williams |first21=B. |hdl=1983/24fe327a-c509-4b6a-aa9a-a22616c42d49 |s2cid=6361097|url=https://dspace.library.uu.nl/bitstream/1874/385704/1/Geological_Record.pdf }}</ref> Of particular concern is the manner in which the combination of acidification with the expected additional stressors of higher [[ocean temperature]]s and [[hypoxia (environmental)|lower oxygen levels]] will impact the seas.<ref name="Gruber2011">{{cite journal|last=Gruber|first=N.|title=Warming up, turning sour, losing breath: ocean biogeochemistry under global change|journal=Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences|volume=369|issue=1943|date=18 April 2011|pages=1980–96|doi=10.1098/rsta.2011.0003|pmid=21502171|bibcode = 2011RSPTA.369.1980G |doi-access=free}}</ref>

===Geological oceanography===
{{Main|Marine geology}}
Geological oceanography is the study of the [[geology]] of the ocean floor including [[plate tectonics]] and [[paleoceanography]].

===Physical oceanography===
{{Main|Physical oceanography}}
Physical oceanography studies the ocean's physical attributes including temperature-salinity structure, mixing, [[ocean surface wave|surface waves]], internal waves, surface [[tide]]s, [[internal tides]], and [[ocean current|currents]]. The following are central topics investigated by physical oceanography.

====Seismic Oceanography====
{{Main|Seismic Oceanography}}

====Ocean currents====
{{Further|Ocean current}}
Since the early ocean expeditions in oceanography, a major interest was the study of ocean currents and temperature measurements. The [[tides]], the [[Coriolis effect]], changes in direction and strength of [[wind]], salinity, and temperature are the main factors determining ocean currents. The [[thermohaline circulation]] (THC) (''thermo-'' referring to [[temperature]] and ''-haline'' referring to [[salinity|salt content]]) connects the ocean basins and is primarily dependent on the [[Water (molecule)#Density of saltwater and ice|density of sea water]]. It is becoming more common to refer to this system as the 'meridional overturning circulation' because it more accurately accounts for other driving factors beyond temperature and salinity. 
*Examples of sustained currents are the [[Gulf Stream]] and the [[Kuroshio Current]] which are [[wind]]-driven [[western boundary currents]].

====Ocean heat content====
[[File:Oceans of Climate Change.ogv|thumbnail|right|[https://climate.nasa.gov/climate_reel/OceansClimateChange640360 Oceans of Climate Change] NASA]]
{{Further|Oceanic heat content}}
[[Oceanic heat content]] (OHC) refers to the extra heat stored in the ocean from changes in [[Earth's energy balance]]. The increase in the ocean heat play an important role in [[sea level rise]], because of [[thermal expansion]]. [[Ocean warming]] accounts for 90% of the energy accumulation associated with [[global warming]] since 1971.<ref>{{cite report |author= IPCC|author-link= Intergovernmental Panel on Climate Change|date= 2013|title= Climate Change 2013: The Physical Science Basis|url= http://www.ipcc.ch/pdf/assessment-report/ar5/wg1/WG1AR5_SPM_FINAL.pdf |archive-url=https://web.archive.org/web/20141029034929/https://www.ipcc.ch/pdf/assessment-report/ar5/wg1/WG1AR5_SPM_FINAL.pdf |archive-date=2014-10-29 |url-status=live|publisher= [[Cambridge University Press]]|page= 8}}</ref><ref>{{cite web |url=https://news.ucar.edu/132773/2020-was-record-breaking-year-ocean-heat |title=2020 was a record-breaking year for ocean heat - Warmer ocean waters contribute to sea level rise and strengthen storms |date=2021-01-13 |author=Laura Snider |publisher=[[National Center for Atmospheric Research]]}}</ref>

===Paleoceanography===
{{Main|Paleoceanography}}
Paleoceanography is the study of the history of the oceans in the geologic past with regard to circulation, chemistry, biology, geology and patterns of sedimentation and biological productivity. Paleoceanographic studies using environment models and different proxies enable the scientific community to assess the role of the oceanic processes in the global climate by the reconstruction of past climate at various intervals. Paleoceanographic research is also intimately tied to palaeoclimatology.