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<p>The eastern Subpolar North Atlantic (SPNA) is crucial to modulate the variation of Atlantic Meridional Overturning Circulation (MOC), by its local gyre circulations and accompanied water mass transformations. Using the trans-basin mooring data in the eastern SPNA, previous studies provided a fundamental understanding to the seasonality of the local MOC. However, the substantial freshening and cooling trend since 2008/2009 could be associated with a potential decadal event in the MOC of the eastern SPNA, though the extent to which these freshwater anomalies influence subpolar overturning variability remains uncertain. To resolve this issue, this study utilizes a high-resolution reanalysis dataset validated against the observations. The time series of the upper limb MOC in the reanalysis presents a pronounced decadal decline in the eastern SPNA (-2.2&#xa0;Sv/decade, 2009–2020), primarily contributed by the Irminger Sea and, more specifically, the region of East Greenland Current (EGC). Decomposition of MOC variations suggests this decline appears linked to an increase in upper limb water volume, likely driven by the upper limb’s freshening in the EGC region. This freshening primarily originates from polar waters transported by the EGC via the Denmark Strait. These findings based on the reanalysis data highlight the sensitivity of MOC to freshwater perturbations in this critical region.</p>

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Decadal decline of the meridional overturning circulation in the eastern subpolar North Atlantic diagnosed from a high-resolution reanalysis dataset

  • 期刊论文

  • 发表日期：

    2026年2月13日

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  • Hanshi Wang,
  • Xiaopei Lin,
  • Jian Shi,
  • Zhenhui Yi,
  • Xingyue Xia,
  • Junwei Chai

摘要

The eastern Subpolar North Atlantic (SPNA) is crucial to modulate the variation of Atlantic Meridional Overturning Circulation (MOC), by its local gyre circulations and accompanied water mass transformations. Using the trans-basin mooring data in the eastern SPNA, previous studies provided a fundamental understanding to the seasonality of the local MOC. However, the substantial freshening and cooling trend since 2008/2009 could be associated with a potential decadal event in the MOC of the eastern SPNA, though the extent to which these freshwater anomalies influence subpolar overturning variability remains uncertain. To resolve this issue, this study utilizes a high-resolution reanalysis dataset validated against the observations. The time series of the upper limb MOC in the reanalysis presents a pronounced decadal decline in the eastern SPNA (-2.2 Sv/decade, 2009–2020), primarily contributed by the Irminger Sea and, more specifically, the region of East Greenland Current (EGC). Decomposition of MOC variations suggests this decline appears linked to an increase in upper limb water volume, likely driven by the upper limb’s freshening in the EGC region. This freshening primarily originates from polar waters transported by the EGC via the Denmark Strait. These findings based on the reanalysis data highlight the sensitivity of MOC to freshwater perturbations in this critical region.