What induced the trend shift of mixed-layer depths in the Antarctic Circumpolar Current region in the mid-1980s?

Shan Liu Jingzhi Su Huijun Wang Cuijuan Sui

Shan Liu, Jingzhi Su, Huijun Wang, Cuijuan Sui. What induced the trend shift of mixed-layer depths in the Antarctic Circumpolar Current region in the mid-1980s?[J]. Acta Oceanologica Sinica. doi: 10.1007/s13131-023-2268-5
Citation: Shan Liu, Jingzhi Su, Huijun Wang, Cuijuan Sui. What induced the trend shift of mixed-layer depths in the Antarctic Circumpolar Current region in the mid-1980s?[J]. Acta Oceanologica Sinica. doi: 10.1007/s13131-023-2268-5

doi: 10.1007/s13131-023-2268-5

What induced the trend shift of mixed-layer depths in the Antarctic Circumpolar Current region in the mid-1980s?

Funds: The National Natural Science Foundation of China under contract Nos 41605052.
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  • Figure  1.  Annual mean (a) MLD (unit: m) and (b) SST (unit: °C) anomaly time series in the ACC region (35°S–65°S) for the period of 1960–2021 (taking 1991 to 2020 as the climatology). The blue and yellow lines are the linear trends for the periods of 1960–1985 and 1986–2021, and the red lines are the 11-yr running mean of the corresponding black lines. The long-term mean (1960-2021) values are shown in the right up corners. (c) (d) and (e) (f) are the same as (a) (b), but for austral winter (August-October) and summer (January-March) respectively.

    Figure  2.  Spatial patterns of the linear MLD trend (shaded areas, m∙a−1) and the MLD long-term mean (black contours, m) for periods (a) 1960–1985 and (b) 1986–2021. (c) is the trend difference between (a) and (b). (d)(e)(f) are the same as (a)(b)(c) but for SST (°C) and its trends (°C∙a−1). (g)-(i) and (j)-(l) are the spatial patterns of MLD and SST in austral winter. The “ave” values are their respective trend mean. The dotted areas exceed the 95% confidence level.

    Figure  3.  Spatial patterns of the linear wind speed trend (m∙s−1∙a−1) in the ACC region for (a) 1960−1985 and (b) 1986−2021. (c) is the difference between (a) and (b). (d)–(f) and (g)–(i) are the same as (a)–(c) but for surface ocean current speed (m∙s−1∙a−1) and wind stress curl (N∙m−3∙a−1). The black contours in (a)(b) are the climatic core position of the ACC (1991−2020). The blue and purple contours in (a)(b)(c) are the trends circumpolar contours for period (a) 1960–1985 and (b) 1986–2021. The contours in (d)–(f) and (g)–(i) are the same as (a)–(c) but for ocean current and wind stress vorticity.

    Figure  4.  The same as Fig. 3, but for austral winter.

    Figure  5.  The annual mean (solid lines) and winter (dashed lines) zonal averaged profiles for climatology (black lines) and trends (blue and purple lines) of (a) surface wind speed (black lines, m∙s−1; blue and purple lines, m∙s−1∙a−1), (b) ocean current speed (black lines, m∙s−1; blue and purple lines, m∙s−1∙a−1), (c) wind stress vorticity (black lines, N∙m−3; blue and purple lines, N∙m−3∙a−1) and (d) MLD (black lines, m; blue and purple lines, m∙a−1) from 40°S to 65°S in the SP sector (70°W–180°). (e)(f)(g)(h) are the same as (a)(b)(c)(d) but for the SI sector (0°–90°E). The climatological values are based on the period of 1991–2020. The blue and purple lines are the corresponding zonal mean trends in the periods 1960–1985 (P1 in the legend) and 1986–2021 (P2 in the legend), respectively.

    Figure  6.  The annual mean and winter standardized time series of MLD (black solid line), wind speed (blue dashed line), ocean current speed (orange dashed line) and wind stress curl meridional gradient (red dashed) in (a) K1 (76°W -150°W, 60°S -68°S) and (b) K2 (50°E -90°E,40°S -50°S) regions. The correlations between MLD and the corresponding variables are given in the following brackets. (c) (d) are the same as (a) (b), but for winter mean.

    Figure  7.  Spatial patterns of the annual mean linear heat flux trend (W∙m−2∙a−1) in the ACC region for (a) 1960–1985 and (b) 1986–2021. (c) is the difference between (a) and (b). (d)(e)(f) are the same as (a)(b)(c) but for freshwater (kg∙m2∙s−1∙a−1). The convention is that downward fluxes are positive.

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出版历程
  • 收稿日期:  2023-06-13
  • 录用日期:  2023-10-10
  • 网络出版日期:  2023-11-27

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