• Alexander, M. A., and C. Deser, 1995: A mechanism for the recurrence of wintertime midlatitude SST anomalies. J. Phys. Oceanogr., 25, 122137, https://doi.org/10.1175/1520-0485(1995)025<0122:AMFTRO>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Alexander, M. A., and J. D. Scott, 2008: The role of Ekman ocean heat transport in the Northern Hemisphere response to ENSO. J. Climate, 21, 56885707, https://doi.org/10.1175/2008JCLI2382.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Alexander, M. A., C. Deser, and M. S. Timlin, 1999: The reemergence of SST anomalies in the North Pacific Ocean. J. Climate, 12, 24192433, https://doi.org/10.1175/1520-0442(1999)012<2419:TROSAI>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Alexander, M. A., M. S. Timlin, and J. D. Scott, 2001: Winter-to-winter recurrence of sea surface temperature, salinity, and mixed layer depth anomalies. Prog. Oceanogr., 49, 4161, https://doi.org/10.1016/S0079-6611(01)00015-5.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Alexander, M. A., I. Bladé, M. Newman, J. R. Lanzante, N.-C. Lau, and J. D. Scott, 2002: The atmospheric bridge: The influence of ENSO teleconnections on air–sea interaction over the global oceans. J. Climate, 15, 22052231, https://doi.org/10.1175/1520-0442(2002)015<2205:TABTIO>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Alizadeh-Choobari, O., 2017: Contrasting global teleconnection features of the eastern Pacific and central Pacific El Niño events. Dyn. Atmos. Oceans, 80, 139154, https://doi.org/10.1016/j.dynatmoce.2017.10.004.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Ashok, K., S. K. Behera, S. A. Rao, H. Weng, and T. Yamagata, 2007: El Niño Modoki and its possible teleconnection. J. Geophys. Res., 112, C11007, https://doi.org/10.1029/2006JC003798.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Barlow, M., S. Nigam, and E. H. Berbery, 2001: ENSO, Pacific decadal variability, and U.S. summertime precipitation, drought, and stream flow. J. Climate, 14, 21052128, https://doi.org/10.1175/1520-0442(2001)014<2105:EPDVAU>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Biondi, F., A. Gershunov, and D. R. Cayan, 2001: North Pacific decadal climate variability since 1661. J. Climate, 14, 510, https://doi.org/10.1175/1520-0442(2001)014<0005:NPDCVS>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Cai, W., and Coauthors, 2018: Increased variability of eastern Pacific El Niño under greenhouse warming. Nature, 564, 201206, https://doi.org/10.1038/s41586-018-0776-9.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Carréric, A., B. Dewitte, W. Cai, A. Capotondi, K. Takahashi, S.-W. Yeh, G. Wang, and V. Guémas, 2020: Change in strong eastern Pacific El Niño events dynamics in the warming climate. Climate Dyn., 54, 901918, https://doi.org/10.1007/s00382-019-05036-0.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Cayan, D. R., M. D. Dettinger, H. F. Diaz, and N. E. Graham, 1998: Decadal variability of precipitation over western North America. J. Climate, 11, 31483166, https://doi.org/10.1175/1520-0442(1998)011<3148:DVOPOW>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Dettinger, M. D., D. R. Cayan, H. F. Diaz, and D. M. Meko, 1998: North–south precipitation patterns in western North America on interannual-to-decadal timescales. J. Climate, 11, 30953111, https://doi.org/10.1175/1520-0442(1998)011<3095:NSPPIW>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Dewitte, B., J. Choi, S.-I. An, and S. Thual, 2012: Vertical structure variability and equatorial waves during central Pacific and eastern Pacific El Niño in a coupled general circulation model. Climate Dyn., 38, 22752289, https://doi.org/10.1007/s00382-011-1215-x.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Fang, J., and X. Yang, 2016: Structure and dynamics of decadal anomalies in the wintertime midlatitude North Pacific ocean–atmosphere system. Climate Dyn., 47, 19892007, https://doi.org/10.1007/s00382-015-2946-x.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Frankignoul, C., P. Müller, and E. Zorita, 1997: A simple model of the decadal response of the ocean to stochastic wind forcing. J. Phys. Oceanogr., 27, 15331546, https://doi.org/10.1175/1520-0485(1997)027<1533:ASMOTD>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Frankignoul, C., N. Sennechael, Y. Kwon, and M. Alexander, 2011: Influence of the meridional shifts of the Kuroshio and the Oyashio Extensions on the atmospheric circulation. J. Climate, 24, 762777, https://doi.org/10.1175/2010JCLI3731.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Freund, M. B., B. J. Henley, D. J. Karoly, H. V. McGregor, N. J. Abram, and D. Dommenget, 2019: Higher frequency of central Pacific El Niño events in recent decades relative to past centuries. Nat. Geosci., 12, 450455, https://doi.org/10.1038/s41561-019-0353-3.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Garfinkel, C. I., M. M. Hurwitz, D. W. Waugh, and A. H. Butler, 2012: Are the teleconnections of Central Pacific and Eastern Pacific El Niño distinct in boreal wintertime? Climate Dyn., 41, 18351852, https://doi.org/10.1007/s00382-012-1570-2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Graf, H. F., and D. Zanchettin, 2012: Central Pacific El Niño, the “subtropical bridge,” and Eurasian climate. J. Geophys. Res., 117, D01102, https://doi.org/10.1029/2011JD016493.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Graham, N. E., 1994: Decadal-scale climate variability in the tropical and North Pacific during the 1970s and 1980s: Observations and model results. Climate Dyn., 10, 135162, https://doi.org/10.1007/BF00210626.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • He, S., H. Wang, and J. Liu, 2013: Changes in the relationship between ENSO and Asia–Pacific midlatitude winter atmospheric circulation. J. Climate, 26, 33773393, https://doi.org/10.1175/JCLI-D-12-00355.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Hu, D., and Z. Guan, 2018: Decadal relationship between the stratospheric Arctic vortex and Pacific decadal oscillation. J. Climate, 31, 33713386, https://doi.org/10.1175/JCLI-D-17-0266.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Huang, B., and Coauthors, 2015: Extended Reconstructed Sea Surface Temperature version 4 (ERSST.v4). Part I: Upgrades and intercomparisons. J. Climate, 28, 911930, https://doi.org/10.1175/JCLI-D-14-00006.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Hurwitz, M. M., P. A. Newman, and C. I. Garfinkel, 2012: On the influence of North Pacific sea surface temperature on the Arctic winter climate. J. Geophys. Res., 117, D19110, https://doi.org/10.1029/2012JD017819.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Jadin, E. A., K. Wei, Y. A. Zyulyaeva, W. Chen, and L. Wang, 2010: Stratospheric wave activity and the Pacific decadal oscillation. J. Atmos. Sol.-Terr. Phys., 72, 11631170, https://doi.org/10.1016/j.jastp.2010.07.009.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Kalnay, E., and Coauthors, 1996: The NCEP/NCAR 40-Year Reanalysis Project. Bull. Amer. Meteor. Soc., 77, 437472, https://doi.org/10.1175/1520-0477(1996)077<0437:TNYRP>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Kao, H. Y., and J. Y. Yu, 2009: Contrasting eastern-Pacific and central-Pacific types of ENSO. J. Climate, 22, 615632, https://doi.org/10.1175/2008JCLI2309.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Krishnan, R., and M. Sugi, 2003: Pacific decadal oscillation and variability of the Indian summer monsoon rainfall. Climate Dyn., 21, 233242, https://doi.org/10.1007/s00382-003-0330-8.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Kwon, Y.-O., and C. Deser, 2007: North Pacific decadal variability in the Community Climate System Model version 2. J. Climate, 20, 24162433, https://doi.org/10.1175/JCLI4103.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Larkin, N. K., and D. E. Harrison, 2005: On the definition of El Niño and associated seasonal average U.S. weather anomalies. Geophys. Res. Lett., 32, L13705, https://doi.org/10.1029/2005GL022738.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Latif, M., and T. P. Barnett, 1994: Causes of decadal climate variability over the North Pacific and North America. Science, 266, 634637, https://doi.org/10.1126/science.266.5185.634.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Latif, M., and T. P. Barnett, 1996: Decadal climate variability over the North Pacific and North America: Dynamics and predictability. J. Climate, 9, 24072423, https://doi.org/10.1175/1520-0442(1996)009<2407:DCVOTN>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Li, Y., and W. S. Tian, 2017: Different impact of central Pacific and eastern Pacific El Niño on the duration of sudden stratospheric warming. Adv. Atmos. Sci., 34, 771782, https://doi.org/10.1007/s00376-017-6286-0.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Liguori, G., and E. Di Lorenzo, 2018: Meridional modes and increasing Pacific decadal variability under anthropogenic forcing. Geophys. Res. Lett., 45, 983991, https://doi.org/10.1002/2017GL076548.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Mantua, N. J., and S. R. Hare, 2002: The Pacific decadal oscillation. J. Oceanogr., 58, 3544, https://doi.org/10.1023/A:1015820616384.

  • Mantua, N. J., S. R. Hare, Y. Zhang, J. M. Wallace, and R. C. Francis, 1997: A Pacific interdecadal climate oscillation with impacts on salmon production. Bull. Amer. Meteor. Soc., 78, 10691079, https://doi.org/10.1175/1520-0477(1997)078<1069:APICOW>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Miller, A. J., and N. Schneider, 2000: Interdecadal climate regime dynamics in the North Pacific Ocean: Theories, observations and ecosystem impacts. Prog. Oceanogr., 47, 355379, https://doi.org/10.1016/S0079-6611(00)00044-6.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Miller, A. J., D. R. Cayan, T. P. Barnett, N. E. Graham, and J. M. Oberhuber, 1994: Interdecadal variability of the Pacific Ocean: Model response to observed heat flux and wind stress anomalies. Climate Dyn., 9, 287302, https://doi.org/10.1007/BF00204744.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Minobe, S., 2000: Spatio-temporal structure of the pentadecadal variability over the North Pacific. Prog. Oceanogr., 47, 381408, https://doi.org/10.1016/S0079-6611(00)00042-2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Miyasaka, T., H. Nakamura, B. Taguchi, and M. Nonaka, 2014: Multidecadal modulations of the low-frequency climate variability in the wintertime North Pacific since 1950. Geophys. Res. Lett., 41, 29482955, https://doi.org/10.1002/2014GL059696.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Namias, J., and R. M. Born, 1970: Temporal coherence in North Pacific sea-surface temperature patterns. J. Geophys. Res., 75, 59525955, https://doi.org/10.1029/JC075i030p05952.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Namias, J., and R. M. Born, 1974: Further studies of temporal coherence in North Pacific sea surface temperatures. J. Geophys. Res., 79, 797798, https://doi.org/10.1029/JC079i006p00797.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Newman, M., G. P. Compo, and M. A. Alexander, 2003: ENSO-forced variability of the Pacific decadal oscillation. J. Climate, 16, 38533857, https://doi.org/10.1175/1520-0442(2003)016<3853:EVOTPD>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Newman, M., and Coauthors, 2016: The Pacific decadal oscillation, revisited. J. Climate, 29, 43994427, https://doi.org/10.1175/JCLI-D-15-0508.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Pak, G., Y.-H. Park, F. Vivier, Y.-O. Kwon, and K.-I. Chang, 2014: Regime-dependent nonstationary relationship between the East Asian winter monsoon and North Pacific Oscillation. J. Climate, 27, 81858204, https://doi.org/10.1175/JCLI-D-13-00500.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Qiu, B., and S. Chen, 2005: Variability of the Kuroshio Extension jet, recirculation gyre, and mesoscale eddies on decadal time scales. J. Phys. Oceanogr., 35, 20902103, https://doi.org/10.1175/JPO2807.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Rayner, N. A., and Coauthors, 2003: Global analyses of sea surface temperature, sea ice, and night marine air temperature since the late nineteenth century. J. Geophys. Res., 108, 4407, https://doi.org/10.1029/2002JD002670.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Sasaki, Y. N., and N. Schneider, 2011: Decadal shifts of the Kuroshio Extension jet: Application of thin-jet theory. J. Phys. Oceanogr., 41, 979993, https://doi.org/10.1175/2010JPO4550.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Sasaki, Y. N., S. Minobe, and N. Schneider, 2013: Decadal response of the Kuroshio Extension jet to Rossby waves: Observation and thin-jet theory. J. Phys. Oceanogr., 43, 442456, https://doi.org/10.1175/JPO-D-12-096.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Schneider, N., and B. D. Cornuelle, 2005: The forcing of the Pacific decadal oscillation. J. Climate, 18, 43554373, https://doi.org/10.1175/JCLI3527.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Shiozaki, M., T. Enomoto, and K. Takaya, 2021: Disparate midlatitude responses to the eastern Pacific El Niño. J. Climate, 34, 773786, https://doi.org/10.1175/JCLI-D-20-0246.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Soulard, N., H. Lin, and B. Yu, 2019: The changing relationship between ENSO and its extratropical response patterns. Sci. Rep., 9, 6507, https://doi.org/10.1038/s41598-019-42922-3.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Taguchi, B., S.-P. Xie, N. Schneider, M. Nonaka, H. Sasaki, and Y. Sasai, 2007: Decadal variability of the Kuroshio Extension: Observations and an eddy-resolving model hindcast. J. Climate, 20, 23572377, https://doi.org/10.1175/JCLI4142.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Taguchi, B., H. Nakamura, M. Nonaka, N. Komori, A. Kuwano-Yoshida, K. Takaya, and A. Goto, 2012: Seasonal evolutions of atmospheric response to decadal SST anomalies in the North Pacific subarctic frontal zone: Observations and a coupled model simulation. J. Climate, 25, 111139, https://doi.org/10.1175/JCLI-D-11-00046.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Tao, L., X. Yang, J. Fang, and X. Sun, 2020: PDO-related wintertime atmospheric anomalies over the midlatitude North Pacific: Local versus remote SST forcing. J. Climate, 33, 69897010, https://doi.org/10.1175/JCLI-D-19-0143.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Trenberth, K. E., 1990: Recent observed interdecadal climate changes in the Northern Hemisphere. Bull. Amer. Meteor. Soc., 71, 988993, https://doi.org/10.1175/1520-0477(1990)071<0988:ROICCI>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Trenberth, K. E., and J. W. Hurrell, 1994: Decadal atmosphere–ocean variations in the Pacific. Climate Dyn., 9, 303319, https://doi.org/10.1007/BF00204745.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Wang, H., and Coauthors, 2015: A review of seasonal climate prediction research in China. Adv. Atmos. Sci., 32, 149168, https://doi.org/10.1007/s00376-014-0016-7.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Wang, L., W. Chen, and R. Huang, 2007: Changes in the variability of North Pacific Oscillation around 1975/1976 and its relationship with East Asian winter climate. J. Geophys. Res., 112, D11110, https://doi.org/10.1029/2006JD008054.

    • Search Google Scholar
    • Export Citation
  • Weng, H., K. Ashok, S. K. Behera, S. A. Rao, and T. Yamagata, 2007: Impacts of recent El Niño Modoki dry/wet conditions in the Pacific Rim during boreal summer. Climate Dyn., 29, 113129, https://doi.org/10.1007/s00382-007-0234-0.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Woo, S. H., M. K. Sung, S. W. Son, and J. S. Kug, 2015: Connection between weak stratospheric vortex events and the Pacific decadal oscillation. Climate Dyn., 45, 34813492, https://doi.org/10.1007/s00382-015-2551-z.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Wu, S., Z. Liu, R. Zhang, and T. Delworth, 2011: On the observed relationship between the Pacific Decadal Oscillation and the Atlantic Multi-decadal Oscillation. J. Oceanogr., 67, 2735, https://doi.org/10.1007/s10872-011-0003-x.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Yeh, S.-W., J.-S. Kug, B. Dewitte, M.-H. Kwon, B. P. Kirkman, and F.-F. Jin, 2009: El Niño in a changing climate. Nature, 461, 511514, https://doi.org/10.1038/nature08316.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Yeh, S.-W., and Coauthors, 2018: ENSO atmospheric teleconnections and their response to greenhouse gas forcing. Rev. Geophys., 56, 185206, https://doi.org/10.1002/2017RG000568.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Zhang, P., Z. Wu, and H. Chen, 2017: Interdecadal variability of the ENSO–North Pacific atmospheric circulation in winter. Atmos.–Ocean, 55, 110120, https://doi.org/10.1080/07055900.2017.1291411.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Zhang, W., and F. Jin, 2012: Improvements in the CMIP5 simulations of ENSO-SSTA meridional width. Geophys. Res. Lett., 39, L23704, https://doi.org/10.1029/2012GL053588.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Zhang, W., J. Li, and F. Jin, 2009: Spatial and temporal features of ENSO meridional scales. Geophys. Res. Lett., 36, L15605, https://doi.org/10.1029/2009GL038672.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Zhang, W., F. Jin, J. Zhao, and J. Li, 2013: On the bias in simulated ENSO SSTA meridional widths of CMIP3 models. J. Climate, 26, 31733186, https://doi.org/10.1175/JCLI-D-12-00347.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Zhao, M., H. H. Hendon, O. Alves, G. Liu, and G. Wang, 2016: Weakened eastern Pacific El Niño predictability in the early twenty-first century. J. Climate, 29, 68056822, https://doi.org/10.1175/JCLI-D-15-0876.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
All Time Past Year Past 30 Days
Abstract Views 252 252 19
Full Text Views 164 164 6
PDF Downloads 187 187 8

Meridional Position Changes of the Sea Surface Temperature Anomalies in the North Pacific

View More View Less
  • 1 a Key Laboratory for Semi-Arid Climate Change of the Ministry of Education, College of Atmospheric Sciences, Lanzhou University, China
  • | 2 b State Key Laboratory of Satellite Ocean Environment Dynamics, Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou, China
  • | 3 c Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, China
  • | 4 d School of Oceanography, Shanghai Jiao Tong University, Shanghai, China
  • | 5 e College of Global Change and Earth System Science, Beijing Normal University, Beijing, China
© Get Permissions Rent on DeepDyve
Restricted access

Abstract

Changes in the meridional position of the sea surface temperature (SST) anomalies (SSTAs) associated with the interannual component (PC1-I) of the principal component 1 (PC1) of the first leading mode of the North Pacific SST (referred to here as PC1-I-related SSTAs) are investigated using reanalysis products and climate model output. It is found that the PC1-I-related SSTAs (or PC1-I anomalies) significantly shift southward at a rate of 1.04° latitude per decade and have moved southward by 4.4° since the 1960s. Our further analysis indicates that the southward shift of the PC1-I-related SSTAs is due to changes in ENSO teleconnections. Compared to the 1950–75 period (PRE era), the meridional width of the ENSO-induced tropical positive geopotential height (GH) anomaly is narrower during the 1991–2016 period (POST era), inducing a southward shift of the subtropical westerly anomaly over the North Pacific through geostrophic wind relations. This southward shift of the westerly anomaly favors the southward shift of the ENSO-induced negative GH anomaly (cyclonic circulation anomaly) over the North Pacific by positive vorticity forcing of the zonal wind shear. The southward-shifting GH anomaly associated with ENSO further forces the PC1-I anomaly to shift southward. Furthermore, the contraction of the ENSO-induced tropical positive GH anomaly is related to the contraction of the meridional width of ENSO. The modeling results support that the decrease in the ENSO meridional width favors the contraction of the ENSO-induced tropical positive GH anomaly and the southward shift of ENSO teleconnections over the North Pacific, contributing to the southward shift of the PC1-I anomaly.

© 2021 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses).

Corresponding author: Wenshou Tian, wstian@lzu.edu.cn

Abstract

Changes in the meridional position of the sea surface temperature (SST) anomalies (SSTAs) associated with the interannual component (PC1-I) of the principal component 1 (PC1) of the first leading mode of the North Pacific SST (referred to here as PC1-I-related SSTAs) are investigated using reanalysis products and climate model output. It is found that the PC1-I-related SSTAs (or PC1-I anomalies) significantly shift southward at a rate of 1.04° latitude per decade and have moved southward by 4.4° since the 1960s. Our further analysis indicates that the southward shift of the PC1-I-related SSTAs is due to changes in ENSO teleconnections. Compared to the 1950–75 period (PRE era), the meridional width of the ENSO-induced tropical positive geopotential height (GH) anomaly is narrower during the 1991–2016 period (POST era), inducing a southward shift of the subtropical westerly anomaly over the North Pacific through geostrophic wind relations. This southward shift of the westerly anomaly favors the southward shift of the ENSO-induced negative GH anomaly (cyclonic circulation anomaly) over the North Pacific by positive vorticity forcing of the zonal wind shear. The southward-shifting GH anomaly associated with ENSO further forces the PC1-I anomaly to shift southward. Furthermore, the contraction of the ENSO-induced tropical positive GH anomaly is related to the contraction of the meridional width of ENSO. The modeling results support that the decrease in the ENSO meridional width favors the contraction of the ENSO-induced tropical positive GH anomaly and the southward shift of ENSO teleconnections over the North Pacific, contributing to the southward shift of the PC1-I anomaly.

© 2021 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses).

Corresponding author: Wenshou Tian, wstian@lzu.edu.cn
Save