Fig. 2: Time series of the SPG index and its lag correlation with subsurface salinity and temperature anomalies for the period 1970–2019. | npj Climate and Atmospheric Science

Fig. 2: Time series of the SPG index and its lag correlation with subsurface salinity and temperature anomalies for the period 1970–2019.

From: North Atlantic subpolar gyre provides downstream ocean predictability

Fig. 2

a Standardized time series of SPG index. Lag correlation between the SPG index and subsurface, b salinity and c temperature at lag years 3–5 (salinity and temperature lag SPG index) in ASSIM. The SPG index is defined as density anomaly at 310 m depth over 55–35°W, 50–62°N [area outlined in black in (b)]. The positive (negative) SPG index indicates strong (weak) SPG circulation and strong (red dots) and weak SPG (blue dots) phases are identified with above 0.5 and below −0.5, respectively. Stippling in (b) and (c) denotes 95% confidence level based on Student’s t test.

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