2.3 Southern Ocean

• Main Authors: Rintoul, SR, Fahrback, E, Abele, D, Ackley, S, Allison, I, Brandt, A, Brussaard, C, Cavanagh, RD, Danis, B, de Baar, H, de Broyer, C, Evans, C, Heywood, K, Hofmann, E, Hoppema, M, Iversen, SA, Johnston, NM, Klepikov, A, Luis, AJ, Murphy, EJ, Segers, H, Strass, V, Summerhayes, C, Tancell, C, Wadley, V, Woodworth, P, Worby, AP, Bowie, AR
• Format: Book Part
• Language: English
• Published: CCI Press in collaboration with the University of the Arctic and ICSU/WMO Joint Committee for International Polar Year 2007-2008 2011
• Subjects: Earth Sciences; Physical Geography and Environmental Geoscience; Physical Geography and Environmental Geoscience not elsewhere classified; Antarctic; Cubillos; Sarmiento; Southern Ocean; The Antarctic; Antarc*; Antarctica; Arctic; Ice Sheet; International Polar Year; IPY; Sea ice
• Online Access: http://www.icsu.org/publications/reports-and-reviews/ipy-summary; http://ecite.utas.edu.au/76088

Recent scientific advances have led to growingrecognition that Southern Ocean processes influenceclimate and biogeochemical cycles on global scales.The Southern Ocean connects the ocean basins andlinks the shallow and deep limbs of the overturningcirculation, a global-scale system of ocean currentsthat influences how much heat and carbon the oceancan store (Rintoul et al., 2001). The upwelling of deepwaters returns carbon (e.g. le Quer et al., 2007) andnutrients (e.g. Sarmiento et al., 2004) to the surfaceocean; the compensating sinking of surface watersinto the ocean interior sequesters carbon and heatand renews oxygen levels. The capacity of the oceanto moderate the pace of climate change is controlledstrongly by the circulation of the Southern Ocean. Thefuture of the Antarctic ice sheet, and therefore sealevelrise, is increasingly understood to be determinedby the rate at which the relatively warm oceancan melt floating glacial ice around the margin ofAntarctica (Rignot and Jacobs, 2002). The expansionand contraction of Antarctic sea ice influences surfacealbedo, air-sea exchange of heat and of gases, suchas carbon dioxide and oxygen, and the habitat for avariety of marine organisms (Thomas and Dieckmann,2002). The Southern Ocean is also home to unique andproductive ecosystems and rich biodiversity.Given the significance of the Southern Ocean to theEarth system, any change in the region would haveimpacts that extend well beyond the high southernlatitudes. Recent studies suggest change is underway:the Southern Ocean is warming and fresheningthroughout most of the ocean depth (Gille, 2008;Bning et al., 2008); major currents are shifting to thesouth, causing regional changes in sea-level (Sokolovand Rintoul, 2009a,b) and the distribution of organisms(Cubillos et al., 2007), and supplying additional heat tomelt ice around the rim of Antarctica (Jacobs, 2006);and the future of the Southern Ocean carbon sink is atopic of vigorous debate (le Quer et al., 2007; Bninget al., 2008). Climate feedbacks involving oceancirculation, changes in sea ice (hence albedo) and thecarbon cycle have the potential to alter rates of climatechange in the future, but the magnitude and likelihoodof such feedbacks remains poorly understood.Progress in understanding Southern Ocean processeshas been slowed by the historical lack of observationsin this remote part of the globe. Growingrecognition of the importance of the Southern Oceanhas resulted in an increasing focus on the region; atthe same time, new technologies have led to greatimprovements in our ability to observe the SouthernOcean. International Polar Year 20072008 effectivelyharnessed the human and logistic resources of theinternational community and exploited technologydevelopments to deliver an unprecedented view ofthe status of the Southern Ocean, provided a baselinefor assessing change and demonstrated the feasibility,value and timeliness of a Southern Ocean ObservingSystem (Chapter 3.3). During IPY, a circumpolar, multidisciplinarysnapshot of the status of the SouthernOcean was obtained for the first time; many properties,processes or regions had not been measured before.Scientists from more than 25 nations participatedin Southern Ocean IPY.Here, we summarize the rationale, field programsand early scientific highlights from IPY programs inthe Southern Ocean to show that the IPY has providedsignificant advances in our understanding of theSouthern Ocean.