资源环境科技发展态势分析平台

Ocean chlorophyll (Chl)-induced heating can affect the climate system through the penetration of solar radiation in the upper ocean. Currently, the ocean biology-induced heating (OBH) feedback effects on the climate in the tropical Pacific are still not well understood, and the mechanisms regarding how SST is modulated remain elusive. In this paper, chlorophyll (Chl) data from satellites are combined with physical fields from Argo profiles to estimate OBH-related fields, including the penetration depth (H-p) and the ocean mixed-layer (ML) depth (H-m). In addition, some directly related heating terms with H-m and H-p are diagnosed, including the absorbed solar radiation component within the ML (denoted as Q(abs)), the rate of ML temperature changes that are directly induced by Q(abs) (denoted as R-sr=Q(abs)/(rho 0CpHm)), and the portion of solar radiation that penetrates through the bottom of the ML (denoted as Q(pen)). The structural relationships between these related fields are examined to illustrate how these heating terms are affected by H-p and H-m. The extent to which R-sr and Q(pen) are modulated by H-p is strikingly different during ENSO cycles. In the western-central equatorial Pacific, inter-annual variations in H-p tend to be out of phase with those in H-m. A decrease (increase) in Q(abs) from a positive (negative) H-p anomaly during El Nino (La Nina) tends to be offset by a negative (positive) H-m anomaly. Thus, R-sr is not closely related with H-p, even though Q(abs) is highly correlated with H-p, indicating that the direct thermal effect through Q(abs) is not a dominant factor that affects the SST. In contrast, the inter-annual variability of Q(pen) in the region is significantly enhanced by that of H-p, with their high positive correlation. The H-p-induced differential heating in the ML and subsurface layers from the Q(pen) and Q(abs) terms modifies the thermal contrast, stratification and vertical mixing, which represent a dominant indirect ocean dynamical effect on the SST. The revealed relationships between these related fields provide an observational basis for gaining structural insights into the OBH feedback effects and validating model simulations in the tropical Pacific.