Heaving Induced by PDO Driving Abyssal Water Decadal Variability in the Eastern Philippine Sea

Abstract

The abyssal ocean serves as a significant heat reservoir in the Earth system, essential for regulating global energy and carbon balance. Previous studies indicate that climate modes primarily affect thermohaline conditions above 1,000 m, but their direct influence on the abyssal ocean remains uncertain. We utilized observations and reanalysis data to identify an inherent correlation between the Pacific Decadal Oscillation (PDO) and potential temperature at depths of 2,000–4,500 dbar in the Eastern Philippine Sea. During its positive (negative) phases, PDO induces warm (cold) anomalies in abyssal water, exhibiting a distinct first baroclinic mode throughout the water column. The heaving process (the vertically adiabatic migration of isopycnals), primarily driven by the divergence of abyssal circulation linked to PDO, emerges as the dominant mechanism influencing the deep-water potential temperature variability. This study reveals that climate modes can rapidly modulate abyssal variability below the depth of 2,000 m.