State and trends of the Southern Ocean

Antarctic environment (2016, 2011)

State and trends of the Southern Ocean

Ocean temperature

This assessment summary component has changed from 2011.

In 2011 only the sea surface temperature was assessed, whereas the 2016 assessment includes the entire water column

The original 2011 summary, grade, trend and confidence levels have been replicated here to assist comparison of changes between reporting cycles.

The Southern Ocean has warmed in recent decades; warming is strongest in the upper ocean

Year(s):

2016

Deteriorating

Confidence (in grade):

Adequate

Confidence (in trend):

Adequate

Comparability (to previous reports):

Comparable

Ocean temperature

20162011

Antarctic environment

State and trends

Approach/Process

Expert consultation was used to determine state and trends.

Data/Information sources

In addition to the references cited in the 'State and trends' section, the following references also support this assessment:

Gille 2008

Gille, S. T. 2008. Decadal-scale temperature trends in the Southern Hemisphere ocean. Journal of Climate, 21, 4749-4765.

Joughin et al. 2014

Joughin I, Smith BE & Medley B (2014). Marine ice sheet collapse potentially under way for the Thwaites Glacier Basin, West Antarctica. Science 344(6185):735–738.

Purkey & Johnson 2010

Purkey SG & Johnson GC (2010). Warming of global abyssal and deep Southern Ocean waters between the 1990s and 2000s: contributions to global heat and sea level rise budgets. Journal of Climate 23(23):6336–6351.

Rhein et al. 2013

Rhein M, Rintoul SR, Aoki S, Campos E, Chambers D, Feely RA, Gulev S, Johnson GC, Josey SA, Kostianoy A, Mauritzen C, Roemmich D, Talley LD & Wang F (2013). Observations: ocean. In: Stocker TF, Qin D, Plattner G-K, Tignor M, Allen SK, Boschung J, Nauels A, Xia Y, Bex V & Midgley PM (eds), Climate change 2013: the physical science basis, contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change, Cambridge University Press, Cambridge, United Kingdom, 255–316.

Rignot et al. 2014

Rignot E, Mouginot J, Morlighem M, Seroussi H & Scheuchl B (2014). Widespread, rapid grounding line retreat of Pine Island, Thwaites, Smith, and Kohler glaciers, West Antarctica, from 1992 to 2011. Geophysical Research Letters 41(10):3502–3509.

Roemmich et al. 2015

Roemmich D, Church J, Gilson J, Monselesan D, Sutton P & Wijffels S (2015). Unabated planetary warming and its ocean structure since 2006. Nature Climate Change 5(3):240–245.

Schmidtko & Johnson 2012

Schmidtko S & Johnson GC (2012). Multi-decadal warming and shoaling of Antarctic intermediate water. Journal of Climate 25(1):201–221.

Comments

Assessment remains the same as in 2011.

Topics

The physical environment: The Southern Ocean

Since 1950, the upper kilometre of the water column and densest part of Antarctic bottom water in the Weddell Sea warmed by 0.2°C at 700-1000 metres between 35°S and 65°S.

Year(s):

2011

Deteriorating

Confidence (in grade):

Adequate

Confidence (in trend):

Adequate

Comparability (to previous reports):

Not assessed

Topics

The physical environment: The Southern Ocean

Ocean acidity

Polar pH levels are changing twice as fast as tropical ones. Pre-industrial acidity has dropped from pH 8.2 to pH 8.1

Year(s):

2016

Deteriorating

Confidence (in grade):

Adequate

Confidence (in trend):

Adequate

Comparability (to previous reports):

Comparable

Ocean acidity

20162011

Antarctic environment

State and trends

Approach/Process

Expert consultation was used to determine state and trends.

Data/Information sources

In addition to the references cited in the 'State and trends' section, the following references also support this assessment:

Constable et al. 2014

Constable AJ, Melbourne-Thomas J, Corney SP, Arrigo KR, Barbraud C, Barnes DKA, Bindoff NL, Boyd PW, Brandt A, Costa DP, Davidson AT, Ducklow HW, Emmerson L, Fukuchi M, Gutt J, Hindell MA, Hofmann EE, Hosie GW, Iida T, Jacob S, Johnston NM, Kawaguchi S, Kokubun N, Koubbi P, Lea MA, Makhado A, Massom RA, Meiners K, Meredith MP, Murphy EJ, Nicol S, Reid K, Richerson K, Riddle MJ, Rintoul SR, Smith WO, Southwell C, Stark JS, Sumner M, Swadling KM, Takahashi KT, Trathan PN, Welsford DC, Weimerskirch H, Westwood KJ, Wienecke BC, Wolf-Gladrow D, Wright SW, Xavier JC & Ziegler P (2014). Climate change and Southern Ocean ecosystems. I: how changes in physical habitats directly affect marine biota. Global Change Biology 20(10):3004–3025.

Frommel et al. 2012

Frommel AY, Maneja R, Lowe D, Malzahn AM, Geffen AJ, Folkvord A, Piatkowski U, Reusch TBH & Clemmesen C (2012). Severe tissue damage in Atlantic cod larvae under increasing ocean acidification. Nature Climate Change 2(1):42–46.

Orr et al. 2005

Orr JC, Fabry VJ, Aumont O, Bopp L, Doney SC, Feely RA, Gnanadesikan A, Gruber N, Ishida A, Joss F, Key RM, Lindsay K, Maier-Reime E, Matear R, Monfray P, Mouchet A, Najjar RG, Plattner G-K, Rodgers KB, Sabine CL, Sarmiento JL, Schlitzer R, Slater RD, Totterdell IJ, Weirig MF, Yamanaka Y & Yool A (2005). Anthropogenic ocean acidification over the twenty-first century and its impact on calcifying organisms. Nature 437:681–686.

Orr et al. 2009

Orr JC, Caldeira K, Fabry V, Gattuso J-P, Haugan P, Lehodey P, Patoja S, Pörtner HO, Riebesell U, Trull T, Urban E, Hood M & Broadgate W (2009). Research priorities for understanding ocean acidification. Oceanography 22:182–189.

Seibel et al. 2012

Seibel BA, Maas AE & Dierssen HM (2012). Energetic plasticity underlies a variable response to ocean acidification in the pteropod, Limacina helicina antarctica. PLoS ONE 7(4):e30464, doi:10.1371/journal.pone.0030464.

Shi et al. 2010

Shi D, Xu Y, Hopkinson BM & Morel FMM (2010). Effect of ocean acidification on iron availability to marine phytoplankton. Science 327:676–679.

Comments

Assessment remains the same as in 2011.

Topics

The physical environment: The Southern Ocean

Polar pH levels are changing twice as fast as tropical ones; pre-industrial pH 8.2 dropped to pH 8.1, indicating increased acidity

Year(s):

2011

Deteriorating

Confidence (in grade):

Adequate

Confidence (in trend):

Adequate

Comparability (to previous reports):

Not assessed

Topics

The physical environment: The Southern Ocean

Ocean salinity

The salinity of the Southern Ocean has reduced in recent decades

Year(s):

2016

Deteriorating

Confidence (in grade):

Adequate

Confidence (in trend):

Adequate

Comparability (to previous reports):

Comparable

Ocean salinity

20162011

Antarctic environment

State and trends

Approach/Process

Expert consultation was used to determine state and trends.

Data/Information sources

In addition to the references cited in the 'State and trends' section, the following references also support this assessment:

Böning et al. 2008

Böning CW, Dispert A, Visbeck M, Rintoul SR & Schwarzkopf FU (2008). The response of the Antarctic Circumpolar Current to recent climate change. Nature Geoscience 1(12):864–869.

Helm et al. 2010

Helm KP, Bindoff NL & Church JA (2010). Changes in the global hydrological-cycle inferred from ocean salinity. Geophysical Research Letters 37(18):L18701, doi:10.1029/2010GL044222.

Rhein et al., 2013

Van Wijk & Rintoul 2014

Van Wijk EM & Rintoul SR (2014). Freshening drives contraction of Antarctic bottom water in the Australian Antarctic Basin. Geophysical Research Letters 41(5):1657–1664.

Comments

Assessment remains the same as in 2011.

Topics

The physical environment: The Southern Ocean

The coastal waters between the Ross Sea and the southern Indian Ocean are fresher now than 50 years ago, making the Antarctic bottom water that forms here less saline

Year(s):

2011

Deteriorating

Confidence (in grade):

Adequate

Confidence (in trend):

Adequate

Comparability (to previous reports):

Not assessed

Topics

The physical environment: The Southern Ocean

Southern Ocean circulation and structure

Changes in wind forcing caused by human activities (ozone depletion and increased greenhouse gases) have driven a polewards shift of Southern Ocean currents, contributing to warming. Antarctic bottom water has warmed, freshened and decreased in volume, and this has likely influenced large-scale circulation. Changes in patterns in sea ice formation and melting may influence shallow overturning near the continent

Year(s):

2016

Deteriorating

Confidence (in grade):

Adequate

Confidence (in trend):

Adequate

Comparability (to previous reports):

Not comparable

Southern Ocean circulation and structure

20162011

Antarctic environment

State and trends

Approach/Process

Expert consultation was used to determine state and trends.

Data/Information sources

In addition to the references cited in the 'State and trends' section, the following references also support this assessment:

Bindoff & Hobbs 2016

Bindoff NL & Hobbs WR (2016). Southern Ocean: sea-ice-driven shallow overturning. Nature Geoscience 9(8):569–570.

Jacobs et al. 2011

Jacobs, S. S., Jenkins, A., Giulivi, C. F. and Dutrieux, P. 2011. Stronger ocean circulation and increased melting under Pine Island Glacier ice shelf. Nature Geoscience, 4, 519-523.

Joughin et al. 2014

Joughin I, Smith BE & Medley B (2014). Marine ice sheet collapse potentially under way for the Thwaites Glacier Basin, West Antarctica. Science 344(6185):735–738.

Purkey & Johnson 2013

Purkey SG & Johnson GC (2013). Antarctic bottom water warming and freshening: contributions to sea level rise, ocean freshwater budgets, and global heat gain. Journal of Climate 26:6105–6122.

Rignot et al. 2014

Takahashi et al. 2009

Takahashi T, Sutherland S, Wanninkhof R, Sweeney C, Feely R, Chipman D, Hales B, Friederich G, Chavez F, Sabine C, Watson A, Bakker D, Schuster U, Metzl N, Yoshikawa-Inoue H, Ishii M, Midorikawa T, Nojiri Y, Körtzingerm A, Steinhoffm T, Hoppema M, Olafsson J, Arnarson T, Tilbrook B, Johannessen T, Olsen A, Bellerby R, Wong C, Delille B, Bates N & deBaar H (2009). Climatological mean and decadal change in surface ocean pCO2, and net sea-air CO2 flux over the global oceans. Deep-Sea Research Part II: Topical Studies in Oceanography 56:554–577.

Comments

Assessment remains the same as in 2011.

Topics

The physical environment: The Southern Ocean

Increase in wind strength is expected to affect the ACC and upwelling of circumpolar deep water, formation of different water masses and gyre activity

Year(s):

2011

Unclear

Confidence (in grade):

Low

Confidence (in trend):

Low

Comparability (to previous reports):

Not assessed

Topics

The physical environment: The Southern Ocean

Sea level

Global sea levels are rising because of uptake of heat by the oceans and run-off from ice caps and glaciers. The rate of sea level change shows regional and global variation with time because of particular aspects of climate variability

Year(s):

2016

Deteriorating

Confidence (in grade):

Adequate

Confidence (in trend):

Adequate

Comparability (to previous reports):

Not comparable

Sea level

20162011

Antarctic environment

State and trends

Approach/Process

Expert consultation was used to determine state and trends.

Data/Information sources

In addition to the references cited in the 'State and trends' section, the following references also support this assessment:

Church et al. 2013

Church, J., Clark, P., Cazenave, A., Gregory, J., Jevrejeva, S., Levermann, A., Merrifield, M., Milne, G., Nerem, R., Nunn, P., Payne, A., Pfeffer, W., Stammer, D. and Unnikrishnan, A. 2013. Sea Level Change. In: Stocker, T. (ed.) Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge, United Kingdom and New York, NY, USA: Cambridge University Press.

Fasullo et al. 2016

Fasullo JT, Nerem RS & Hamlington B (2016). Is the detection of accelerated sea level rise imminent? Scientific Reports 6:31245, doi:10.1038/srep31245.

Purkey & Johnson 2010

Rhein et al. 2013

Roemmich et al. 2015

Roemmich D, Church J, Gilson J, Monselesan D, Sutton P & Wijffels S (2015). Unabated planetary warming and its ocean structure since 2006. Nature Climate Change 5(3):240–245.

Comments

Assessment remains the same as in 2011.

Topics

The physical environment: The Southern Ocean

In December 2009, data were obtained from about 135 locations from 250 tide gauges, but large gaps still exist in datasets

Sea level changes are not expected to be uniform across Earth. Sea level rise in the Southern Ocean south of the ACC is predicted to be less than in the Arctic

Year(s):

2011

Unclear

Confidence (in grade):

Low

Confidence (in trend):

Low

Comparability (to previous reports):

Not assessed

Topics

The physical environment: The Southern Ocean

ACC = Antarctic Circumpolar Current

Assessment Summary Key

Grades

Very good

There are no significant changes in physical and/or chemical processes as a result of human activities

Good

There are some significant changes in physical and/or chemical processes as a result of human activities

Poor

There are substantial changes in physical and/or chemical processes as a result of human activities that significantly affect ecosystem functions in some areas

Very poor

There are substantial changes in physical and/or chemical processes as a result of human activities that significantly affect ecosystem functions in much of the region

Recent Trends

Improving
Stable
Deteriorating
Unclear

Confidence

Adequate: Adequate high-quality evidence and high level of consensus
Somewhat adequate: Adequate high-quality evidence or high level of consensus
Limited: Limited evidence or limited consensus
Very limited: Limited evidence and limited consensus
Low: Evidence and consensus too low to make an assessment

Comparability

Comparable: Grade and trend are comparable to the previous assessment
Somewhat comparable: Grade and trend are somewhat comparable to the previous assessment
Not comparable: Grade and trend are not comparable to the previous assessment
Not previously assessed

Klekociuk A, Wienecke B (2016). Antarctic environment: State and trends of the Southern Ocean. In: Australia state of the environment 2016, Australian Government Department of the Environment and Energy, Canberra, https://soe.environment.gov.au/assessment-summary-73-state-and-trends-southern-ocean, DOI 10.4226/94/58b65b2b307c0

The assessment summaries in State of the Environment reporting provide snapshots of key information, and focus on identifying areas for continued or more concentrated attention on strengthening environmental systems to cope with pressures in the future. Assessment summaries are provided for state and trend, pressures and management responses in each of the themes. The summary text in the assessment tables should be read in conjunction with the explanatory text in each section of the theme chapters.

The authors have indicated the strength of the evidence for assessments with a ‘level of confidence’. If adequate high-quality data were available or consensus was high, confidence is indicated as high. If there were only limited data or consensus to determine grades, confidence is indicated as low. Where data are insufficient to attempt scores, this is also indicated, and the component remains on the list to remind readers that it is still an important aspect of the Australian environment, and that more information is needed to improve our understanding and capacity to respond to environmental challenges.

State and trends of the Southern Ocean