Editing Oxygen minimum zone (section)

== Changes ==
OMZs have changed over time due to effects from numerous global chemical and biological processes.<ref>{{Cite web|url=https://oceanservice.noaa.gov/facts/deadzone.html|title=What is a dead zone?|last=US Department of Commerce|first=National Oceanic and Atmospheric Administration|website=oceanservice.noaa.gov|language=EN-US|access-date=2019-11-13}}</ref> To assess these changes, scientists utilize climate models and sediment samples to understand changes to dissolved oxygen in OMZs.<ref name=":2">{{Cite journal|last1=Stramma|first1=Lothar|last2=Schmidtko|first2=Sunke|last3=Levin|first3=Lisa A.|last4=Johnson|first4=Gregory C.|date=April 2010|title=Ocean oxygen minima expansions and their biological impacts|journal=Deep Sea Research Part I: Oceanographic Research Papers|volume=57|issue=4|pages=587–595|doi=10.1016/j.dsr.2010.01.005|bibcode=2010DSRI...57..587S|issn=0967-0637}}</ref> Many recent studies of OMZs have focused on their fluctuations over time and how they may be currently changing as a result of [[climate change]].<ref name=":2" /><ref name=":1">{{Cite journal|last1=van Geen|first1=A.|last2=Smethie|first2=W. M.|last3=Horneman|first3=A.|last4=Lee|first4=H.|date=2006-10-07|title=Sensitivity of the North Pacific oxygen minimum zone to changes in ocean circulation: A simple model calibrated by chlorofluorocarbons|journal=Journal of Geophysical Research|volume=111|issue=C10|pages=C10004|doi=10.1029/2005jc003192|bibcode=2006JGRC..11110004V|issn=0148-0227|doi-access=free}}</ref>

=== In geological time scales ===
Some research has aimed to understand how OMZs have changed over [[Geologic time scale|geological time scales]].<ref name=":1" /> Throughout the history of Earth's oceans, OMZs have fluctuated on long time scales, becoming larger or smaller depending on multiple variables.<ref name=":7">{{Cite journal|last1=Cartapanis|first1=Olivier|last2=Tachikawa|first2=Kazuyo|last3=Bard|first3=Edouard|date=2011-10-29|title=Northeastern Pacific oxygen minimum zone variability over the past 70 kyr: Impact of biological production and oceanic ventilation|journal=Paleoceanography|volume=26|issue=4|pages=PA4208|doi=10.1029/2011pa002126|bibcode=2011PalOc..26.4208C|issn=0883-8305|doi-access=free}}</ref> The factors that change OMZs are the amount of oceanic [[primary production]] resulting in increased respiration at greater depths, changes in the oxygen supply due to poor ventilation, and amount of oxygen supplied through [[thermohaline circulation]].<ref name=":7" />

=== Since industrialization ===
{{excerpt|Ocean deoxygenation#Role of climate change}}