The connection of phytoplankton biomass in the Marguerite Bay polynya of the western Antarctic peninsula to the Southern Annular Mode

Ning Jiang Zhaoru Zhang Ruifeng Zhang Chuning Wang Meng Zhou

Ning Jiang, Zhaoru Zhang, Ruifeng Zhang, Chuning Wang, Meng Zhou. The connection of phytoplankton biomass in the Marguerite Bay polynya of the western Antarctic peninsula to the Southern Annular Mode[J]. Acta Oceanologica Sinica. doi: 10.1007/s13131-023-2201-y
Citation: Ning Jiang, Zhaoru Zhang, Ruifeng Zhang, Chuning Wang, Meng Zhou. The connection of phytoplankton biomass in the Marguerite Bay polynya of the western Antarctic peninsula to the Southern Annular Mode[J]. Acta Oceanologica Sinica. doi: 10.1007/s13131-023-2201-y

doi: 10.1007/s13131-023-2201-y

The connection of phytoplankton biomass in the Marguerite Bay polynya of the western Antarctic peninsula to the Southern Annular Mode

Funds: The Key Research & Development Program of the Ministry of Science and Technology of China under contract No. 2022YFC2807601; the National Natural Science Foundation of China under contract Nos 41941008 and 41876221; the Shanghai Science and Technology Committee under contract Nos 20230711100 and 21QA1404300; the Impact and Response of Antarctic Seas to Climate Change under contract No. IRASCC 1-02-01B; the National Key Research and Development Program of China under contract No. 2019YFC1509102; the Shanghai Frontiers Science Center of Polar (SCOPS); the Shanghai Pilot Program for Basic Research-Shanghai Jiao Tong University under contract No. 21TQ1400201.
More Information
    • 关键词:
    •  / 
    •  / 
    •  / 
    •  / 
    •  
  • Figure  1.  Location of the numerical model domain in the Southern Ocean (red box) (a), location of the Marguerite Bay polynya area in the model domain (red box) (b), and distribution of the satellite-observed summer-mean sea ice concentration in the Marguerite Bay averaged over 2001–2020 (c). The white dashed rectangle represents the selected box enclosing the polynya, and the red line represents the 20% contour of sea ice concentration. The Pal LTER CTD sampling stations within the polynya area are shown by the plus markers (yellow: 2001; blue: 2002; black: 2003; red: 2004; green: 2005 and 2015; white: 2007, 2008, 2011 and 2017; purple: 2014 and 2018. Stations in different years labeled by the same color are very close to each other, but not at the exact locations). Temperature and salinity data were collected at all stations in the 12 years mentioned above, while Chl-a data were only collected in 2001, 2003, 2005, 2007, 2014, 2015 and 2018.

    Figure  2.  Taylor diagrams of comparisons between modelled and observed physical parameters in the Marguerite Bay polynya. a. The comparison between modelled and observed temperature (from Pal LTER; Fig. 1). b. The comparison between modelled and observed salinity (from Pal LTER). c. The comparison between modelled and calculated mixed layer depth (MLD) based on temperature and salinity in-situ measurements. d. The comparison between modelled and satellite-observed spring sea ice concentration (SIC). e. The comparison between modelled and satellite-observed summer sea ice concentration. f. The comparison between modelled and satellite-observed summer sea surface temperature (SST). The red plus markers indicate the information of correlation coefficients, standard deviations and root mean square errors of the modeled data; the closer they are to the Observations (Obs), the smaller the errors between the modeled and observed data are.

    Figure  3.  The modelled and satellite-observed annual cycles of area-mean sea ice concentration in the Marguerite Bay polynya for the years 2001–2020. The correlation coefficient and p-value are shown.

    Figure  4.  Time series of the satellite-observed summer-mean chlorophyll-a (Chl-a) concentration averaged over the Marguerite Bay polynya (green lines) and the winter (a), spring (b), and summer (c) SAM indices (SAMI; black lines) for 2001–2020. The correlation coefficients, p-values, and standard deviations of Chl-a (vertical bars) are shown.

    Figure  5.  Time series of the modelled spring (a) and summer (b) mean mixed layer depth (MLD) and summer-mean chlorophyll-a (Chl-a) concentration averaged over the Marguerite Bay polynya for 2001–2020. The correlation coefficients, p-values, and standard deviations (vertical bars) are shown.

    Figure  6.  Spatial distributions of the modelled spring-mean mixed layer depth (MLD) in the Marguerite Bay polynya during years with low spring SAM index (SAMI) (a–e) and high spring SAM index (f–j), and time series of spring SAM index and spring MLD in the MBP for 2001–2020 (k). In a–j, the SAM indices are labeled in the upper left corner of the panels. In k, the correlation coefficient, p-value, and standard deviations of MLD (vertical bars) are also shown.

    Figure  7.  Time series of the modelled spring-mean sea surface salinity (SSS) and mixed layer depth (MLD) (a), sea surface salinity and surface density (SD) (b), and mixed layer depth and surface density (c) in the Marguerite Bay polynya for 2001–2020. The correlation coefficients, p-values, and standard deviations (vertical bars) are shown.

    Figure  8.  Time series of spring-mean precipitation rate (from ERA5) and sea surface salinity (SSS; modelled) (a), precipitation rate and SAM index (SAMI) (b), precipitation rate and surface air temperature (SAT; from ERA5) (c), and SAT and SAM index (d) for the Marguerite Bay polynya during 2001–2020. The correlation coefficients, p-values, and standard deviations (vertical bars) are shown.

    Figure  9.  The vertical profiles of chlorophyll-a (Chl-a) concentration at the 7 Pal LTER stations (Fig. 1) in 2001–2018.

    Figure  10.  The annual cycle of modelled mixed layer depth in the Marguerite Bay polynya for the years 2001–2020.

    Figure  11.  Schematic for the mechanisms linking the interannual variations of summer phytoplankton biomass in the Marguerite Bay polynya and spring SAM. The yellow dots represent iron (Fe), and the green dots represent phytoplankton biomass.

  • Annett A L, Fitzsimmons J N, Séguret M J M, et al. 2017. Controls on dissolved and particulate iron distributions in surface waters of the Western Antarctic Peninsula shelf. Marine Chemistry, 196: 81–97. doi: 10.1016/j.marchem.2017.06.004
    Annett A L, Skiba M, Henley S F, et al. 2015. Comparative roles of upwelling and glacial iron sources in Ryder Bay, coastal western Antarctic Peninsula. Marine Chemistry, 176: 21–33. doi: 10.1016/j.marchem.2015.06.017
    Arblaster J M, Meehl G A. 2006. Contributions of external forcings to southern annular mode trends. Journal of Climate, 19(12): 2896–2905. doi: 10.1175/JCLI3774.1
    Ardelan M V, Holm-Hansen O, Hewes C D, et al. 2010. Natural iron enrichment around the Antarctic Peninsula in the Southern Ocean. Biogeosciences, 7(1): 11–25. doi: 10.5194/bg-7-11-2010
    Arrigo K R, DiTullio G R, Dunbar R B, et al. 2000. Phytoplankton taxonomic variability in nutrient utilization and primary production in the Ross Sea. Journal of Geophysical Research: Oceans, 105(C4): 8827–8846. doi: 10.1029/1998JC000289
    Arrigo K R, Mills M M, Kropuenske L R, et al. 2010. Photophysiology in two major southern ocean phytoplankton taxa: photosynthesis and growth of Phaeocystis antarctica and Fragilariopsis cylindrus under different irradiance levels. Integrative and Comparative Biology, 50(6): 950–966. doi: 10.1093/icb/icq021
    Arrigo K R, van Dijken G L. 2003. Phytoplankton dynamics within 37 Antarctic coastal polynya systems. Journal of Geophysical Research: Oceans, 108(C8): 3271. doi: 10.1029/2002JC001739
    Arrigo K R, van Dijken G L, Alderkamp A C, et al. 2017. Early spring phytoplankton dynamics in the western Antarctic Peninsula. Journal of Geophysical Research: Oceans, 122(12): 9350–9369. doi: 10.1002/2017JC013281
    Arrigo K R, van Dijken G L, Strong A L. 2015. Environmental controls of marine productivity hot spots around Antarctica. Journal of Geophysical Research: Oceans, 120(8): 5545–5565. doi: 10.1002/2015JC010888
    Atkinson A, Siegel V, Pakhomov E, et al. 2004. Long-term decline in krill stock and increase in salps within the Southern Ocean. Nature, 432(7013): 100–103. doi: 10.1038/nature02996
    Becquevort S, Smith Jr W O. 2001. Aggregation, sedimentation and biodegradability of phytoplankton-derived material during spring in the Ross Sea, Antarctica. Deep-Sea Research Part II: Topical Studies in Oceanography, 48(19–20): 4155–4178
    Bown J, Laan P, Ossebaar S, et al. 2017. Bioactive trace metal time series during Austral Summer in Ryder Bay, Western Antarctic Peninsula. Deep-Sea Research Part II: Topical Studies in Oceanography, 139: 103–119. doi: 10.1016/j.dsr2.2016.07.004
    Bown J, van Haren H, Meredith M P, et al. 2018. Evidences of strong sources of DFe and DMn in ryder bay, western antarctic peninsula. Philosophical Transactions of the Royal Society A Mathematical, Physical and Engineering Sciences, 376(2122): 20170172
    Bromwich D, Liu Z, Rogers A N, et al. 1998. Winter atmospheric forcing of the Ross Sea polynya. In: Jacobs S S, Weiss R F, eds. Ocean, Ice, and Atmosphere: Interactions at the Antarctic Continental Margin. Washington: American Geophysical Union, 101–133
    Bromwich D H, Nicolas J P, Monaghan A J, et al. 2012. Central West Antarctica among the most rapidly warming regions on Earth. Nature Geoscience, 6(2): 139–145
    Budgell W P. 2005. Numerical simulation of ice-ocean variability in the Barents Sea region. Ocean Dynamics, 55(3): 370–387
    Budillon G, Fusco G, Spezie G. 2000. A study of surface heat fluxes in the Ross Sea (Antarctica). Antarctic Science, 12(2): 243–254. doi: 10.1017/S0954102000000298
    Butler A H, Thompson D W J, Gurney K R. 2007. Observed relationships between the southern annular mode and atmospheric carbon dioxide. Global Biogeochemical Cycles, 21(4): GB4014
    Clarke A, Meredith M P, Wallace M I, et al. 2008. Seasonal and interannual variability in temperature, chlorophyll and macronutrients in northern Marguerite Bay, Antarctica. Deep-Sea Research Part II: Topical Studies in Oceanography, 55(18–19): 1988–2006
    Dare R A, Atkinson B W. 2000. Atmospheric response to spatial variations in concentration and size of polynyas in the Southern Ocean sea-ice zone. Boundary-Layer Meteorology, 94(1): 65–88. doi: 10.1023/A:1002442212593
    Dinniman M S, Klinck J M, Hofmann E E. 2012. Sensitivity of Circumpolar Deep Water transport and ice shelf basal melt along the West Antarctic Peninsula to changes in the winds. Journal of Climate, 25(14): 4799–4816. doi: 10.1175/JCLI-D-11-00307.1
    Dinniman M S, Klinck J M, Smith Jr W O. 2007. Influence of sea ice cover and icebergs on circulation and water mass formation in a numerical circulation model of the Ross Sea, Antarctica. Journal of Geophysical Research: Oceans, 112(C11): C11013. doi: 10.1029/2006JC004036
    Dong Shenfu, Sprintall J, Gille S T, et al. 2008. Southern Ocean mixed-layer depth from Argo float profiles. Journal of Geophysical Research: Oceans, 113(C6): C06013
    Ducklow H W, Fraser W R, Meredith M P, et al. 2013. West Antarctic peninsula: an ice-dependent coastal marine ecosystem in transition. Oceanography, 26(3): 190–203. doi: 10.5670/oceanog.2013.62
    Fairall C W, Bradley E F, Hare J E, et al. 2003. Bulk parameterization of air-sea fluxes: Updates and verification for the COARE algorithm. Journal of Climate, 16(4): 571–591. doi: 10.1175/1520-0442(2003)016<0571:BPOASF>2.0.CO;2
    Fyfe J C. 2003. Separating extratropical zonal wind variability and mean change. Journal of Climate, 16(5): 863–874. doi: 10.1175/1520-0442(2003)016<0863:SEZWVA>2.0.CO;2
    Garibotti I A, Vernet M, Ferrario M E, et al. 2003. Phytoplankton spatial distribution patterns along the western Antarctic Peninsula (Southern Ocean). Marine Ecology Progress Series, 261: 21–39. doi: 10.3354/meps261021
    Gillett N P, Thompson D W J. 2003. Simulation of recent southern hemisphere climate change. Science, 302(5643): 273–275. doi: 10.1126/science.1087440
    Graham J A, Dinniman M S, Klinck J M. 2016. Impact of model resolution for on-shelf heat transport along the West Antarctic Peninsula. Journal of Geophysical Research: Oceans, 121(10): 7880–7897. doi: 10.1002/2016JC011875
    Gupta A S, England M H. 2006. Coupled ocean-atmosphere-ice response to variations in the southern annular mode. Journal of Climate, 19(18): 4457–4486. doi: 10.1175/JCLI3843.1
    Haidvogel D B, Arango H, Budgell W P, et al. 2008. Ocean forecasting in terrain-following coordinates: Formulation and skill assessment of the Regional Ocean Modeling System. Journal of Computational Physics, 227(7): 3595–3624. doi: 10.1016/j.jcp.2007.06.016
    Häkkinen S, Mellor G L. 1992. Modeling the seasonal variability of a coupled Arctic ice-ocean system. Journal of Geophysical Research: Oceans, 97(C12): 20285–20304. doi: 10.1029/92JC02037
    Hall A, Visbeck M. 2002. Synchronous variability in the southern hemisphere atmosphere, sea ice, and ocean resulting from the annular mode. Journal of Climate, 15(21): 3043–3057. doi: 10.1175/1520-0442(2002)015<3043:SVITSH>2.0.CO;2
    Hamre B, Stamnes J J, Frette B, et al. 2008. Could stratospheric ozone depletion lead to enhanced aquatic primary production in the polar regions?. Limnology and Oceanography, 53(1): 332–338. doi: 10.4319/lo.2008.53.1.0332
    Hansen J, Ruedy R, Glascoe J, et al. 1999. GISS analysis of surface temperature change. Journal of Geophysical Research: Atmospheres, 104(D24): 30997–31022. doi: 10.1029/1999JD900835
    Holland D M, Jenkins A. 1999. Modeling thermodynamic ice-ocean interactions at the base of an ice shelf. Journal of Physical Oceanography, 29(8): 1787–1800. doi: 10.1175/1520-0485(1999)029<1787:MTIOIA>2.0.CO;2
    Huang Kuan, Ducklow H, Vernet M, et al. 2012. Export production and its regulating factors in the West Antarctica Peninsula region of the Southern Ocean. Global Biogeochemical Cycles, 26(2): GB2005
    Hunke E C, Dukowicz J K. 1997. An elastic-viscous-plastic model for sea ice dynamics. Journal of Physical Oceanography, 27(9): 1849–1867. doi: 10.1175/1520-0485(1997)027<1849:AEVPMF>2.0.CO;2
    Jiang Mingshun, Measures C I, Barbeau K A, et al. 2019. Fe sources and transport from the Antarctic Peninsula shelf to the southern Scotia Sea. Deep-Sea Research Part I: Oceanographic Research Papers, 150: 103060. doi: 10.1016/j.dsr.2019.06.006
    Joy-Warren H L, van Dijken G L, Alderkamp A C, et al. 2019. Light is the primary driver of early season phytoplankton production along the western Antarctic Peninsula. Journal of Geophysical Research: Oceans, 124(11): 7375–7399. doi: 10.1029/2019JC015295
    Karnovsky N, Ainley D G, Lee P. 2007. Chapter 12 the impact and importance of production in polynyas to top-trophic predators: Three case histories. Elsevier Oceanography Series, 74: 391–410
    La H S, Park K. 2016. The Evident Role of Clouds on Phytoplankton Abundance in Antarctic Coastal Polynyas. Terrestrial Atmospheric and Oceanic Sciences, 27(2): 293–301. doi: 10.3319/TAO.2015.11.30.01(Oc)
    Lefebvre W, Goosse H, Timmermann R, et al. 2004. Influence of the southern annular mode on the sea ice-ocean system. Journal of Geophysical Research: Oceans, 109(C9): C09005
    Li Xichen, Cai Wenju, Meehl G A, et al. 2021. Tropical teleconnection impacts on Antarctic climate changes. Nature Reviews Earth & Environment, 2(10): 680–698
    Li Yun, Ji Rubao, Jenouvrier S, et al. 2016. Synchronicity between ice retreat and phytoplankton bloom in circum-Antarctic polynyas. Geophysical Research Letters, 43(5): 2086–2093. doi: 10.1002/2016GL067937
    Marini C, Frankignoul C, Mignot J. 2011. Links between the southern annular mode and the Atlantic meridional overturning circulation in a climate model. Journal of Climate, 24(3): 624–640. doi: 10.1175/2010JCLI3576.1
    Marshall G J. 2003. Trends in the southern annular mode from observations and reanalyses. Journal of Climate, 16(24): 4134–4143. doi: 10.1175/1520-0442(2003)016<4134:TITSAM>2.0.CO;2
    Marshall J, Speer K. 2012. Closure of the meridional overturning circulation through Southern Ocean upwelling. Nature Geoscience, 5(3): 171–180. doi: 10.1038/ngeo1391
    Massom R A, Harris P T, Michael K J, et al. 1998. The distribution and formative processes of latent-heat polynyas in East Antarctica. Annals of Glaciology, 27: 420–426. doi: 10.3189/1998AoG27-1-420-426
    Measures C I, Brown M T, Selph K E, et al. 2013. The influence of shelf processes in delivering dissolved iron to the HNLC waters of the Drake Passage, Antarctica. Deep-Sea Research Part II: Topical Studies in Oceanography, 90: 77–88. doi: 10.1016/j.dsr2.2012.11.004
    Mellor G L, Kantha L. 1989. An ice-ocean coupled model. Journal of Geophysical Research: Oceans, 94(C8): 10937–10954. doi: 10.1029/JC094iC08p10937
    Montes-Hugo M, Doney S C, Ducklow H W, et al. 2009. Recent changes in phytoplankton communities associated with rapid regional climate change along the western Antarctic peninsula. Science, 323(5920): 1470–1473. doi: 10.1126/science.1164533
    Montes-Hugo M A, Yuan Xiaojun. 2012. Climate patterns and phytoplankton dynamics in Antarctic latent heat polynyas. Journal of Geophysical Research: Oceans, 117(C5): C05031
    Moreau S, Mostajir B, Bélanger S, et al. 2015. Climate change enhances primary production in the western Antarctic Peninsula. Global Change Biology, 21(6): 2191–2205. doi: 10.1111/gcb.12878
    Pezza A B, Rashid H A, Simmonds I. 2012. Climate links and recent extremes in Antarctic sea ice, high-latitude cyclones, southern annular mode and ENSO. Climate Dynamics, 38(1): 57–73
    Planquette H, Sherrell R M, Stammerjohn S, et al. 2013. Particulate iron delivery to the water column of the Amundsen Sea, Antarctica. Marine Chemistry, 153: 15–30. doi: 10.1016/j.marchem.2013.04.006
    Polvani L M, Waugh D W, Correa G J P, et al. 2011. Stratospheric ozone depletion: the main driver of twentieth-century atmospheric circulation changes in the southern hemisphere. Journal of Climate, 24(3): 795–812. doi: 10.1175/2010JCLI3772.1
    Roberts A, Allison I, Lytle V I. 2001. Sensible- and latent-heat-flux estimates over the Mertz Glacier polynya, East Antarctica, from in-flight Measurements. Annals of Glaciology, 33: 377–384. doi: 10.3189/172756401781818112
    Saba G K, Fraser W R, Saba V S, et al. 2014. Winter and spring controls on the summer food web of the coastal West Antarctic Peninsula. Nature Communications, 5: 4318. doi: 10.1038/ncomms5318
    Schmidtko S, Johnson G C, Lyman J M. 2013. MIMOC: A global monthly isopycnal upper-ocean climatology with mixed layers. Journal of Geophysical Research: Oceans, 118(4): 1658–1672. doi: 10.1002/jgrc.20122
    Screen J A, Gillett N P, Karpechko A Y, et al. 2010. Mixed layer temperature response to the southern annular mode: mechanisms and model representation. Journal of Climate, 23(3): 664–678. doi: 10.1175/2009JCLI2976.1
    Shchepetkin A F, McWilliams J C. 2009. Correction and commentary for “Ocean forecasting in terrain-following coordinates: Formulation and skill assessment of the regional ocean modeling system” by Haidvogel et al., J. Comp. Phys. 227, pp. 3595–3624. Journal of Computational Physics, 228(24): 8985–9000. doi: 10.1016/j.jcp.2009.09.002
    Simpkins G R, Ciasto L M, Thompson D W J, et al. 2012. Seasonal relationships between large-scale climate variability and Antarctic sea ice concentration. Journal of Climate, 25(16): 5451–5469. doi: 10.1175/JCLI-D-11-00367.1
    Smith Jr W, Gosselin M, Legendre L, et al. 1997. New production in the Northeast Water Polynya: 1993. Journal of Marine Systems, 10(1–4): 199–209
    Smith R C, Martinson D G, Stammerjohn S E, et al. 2008. Bellingshausen and western Antarctic Peninsula region: pigment biomass and sea-ice spatial/temporal distributions and interannual variabilty. Deep-Sea Research Part II: Topical Studies in Oceanography, 55(18–19): 1949–1963
    Spearman C. 1904. The proof and measurement of association between two things. The American Journal of Psychology, 15(1): 72–101. doi: 10.2307/1412159
    Steele M, Mellor G L, McPhee M G. 1989. Role of the molecular sublayer in the melting or freezing of sea ice. Journal of Physical Oceanography, 19(1): 139–147. doi: 10.1175/1520-0485(1989)019<0139:ROTMSI>2.0.CO;2
    Steinberg D K, Ruck K E, Gleiber M R, et al. 2015. Long-term (1993–2013) changes in macrozooplankton off the western Antarctic Peninsula. Deep-Sea Research Part I: Oceanographic Research Papers, 101: 54–70. doi: 10.1016/j.dsr.2015.02.009
    Tagliabue A, Sallée J B, Bowie A R, et al. 2014. Surface-water iron supplies in the Southern Ocean sustained by deep winter mixing. Nature Geoscience, 7(4): 314–320. doi: 10.1038/ngeo2101
    Talley L D. 2011. Descriptive Physical Oceanography: An Introduction. Amsterdam: Academic Press
    Tamura T, Ohshima K I, Fraser A D, et al. 2016. Sea ice production variability in Antarctic coastal polynyas. Journal of Geophysical Research: Oceans, 121(5): 2967–2979. doi: 10.1002/2015JC011537
    Taylor K E. 2001. Summarizing multiple aspects of model performance in a single diagram. Journal of Geophysical Research: Atmospheres, 106(D7): 7183–7192. doi: 10.1029/2000JD900719
    Thompson D W J, Wallace J M. 2000. Annular modes in the extratropical circulation. Part I: Month-to-month variability. Journal of Climate, 13(5): 1000–1016. doi: 10.1175/1520-0442(2000)013<1000:AMITEC>2.0.CO;2
    Turner J, Phillips T, Hosking J S, et al. 2013. The Amundsen sea low. International Journal of Climatology, 33(7): 1818–1829. doi: 10.1002/joc.3558
    Vernet M, Martinson D, Iannuzzi R, et al. 2008. Primary production within the sea-ice zone west of the Antarctic Peninsula: I-sea ice, summer mixed layer, and irradiance. Deep-Sea Research Part II: Topical Studies in Oceanography, 55(18/19): 2068–2085
    Zhang Zhaoru, Hofmann E E, Dinniman M S, et al. 2020. Linkage of the physical environments in the northern Antarctic Peninsula region to the Southern Annular Mode and the implications for the phytoplankton production. Progress in Oceanography, 188: 102416. doi: 10.1016/j.pocean.2020.102416
    Zhang Zhaoru, Uotila P, Stössel A, et al. 2018. Seasonal southern hemisphere multi-variable reflection of the southern annular mode in atmosphere and ocean reanalyses. Climate Dynamics, 50(3): 1451–1470
    Zweng M M, Reagan J R, Antonov J I, et al. 2013. World Ocean Atlas 2013. Volume 2: Salinity. In: Levitus S, Mishonov A, ed. NOAA Atlas NESDIS74. Washington: Government Printing Office
  • 加载中
图(11)
计量
  • 文章访问数:  297
  • HTML全文浏览量:  123
  • PDF下载量:  34
  • 被引次数: 0
出版历程
  • 收稿日期:  2022-09-16
  • 录用日期:  2023-02-03
  • 网络出版日期:  2023-07-18

目录

    /

    返回文章
    返回