Interannual Variability in the Tropical Atlantic and Linkages to the Pacific

Abstract

The variability of sea surface temperature anomalies (SSTAs) in the tropical Atlantic is examined using data from 1900 to the present. SSTAs are filtered to focus on the interannual band with fluctuations less than 60 months. Both SSTAs over the northern tropical Atlantic (NTA) and the southern tropical Atlantic (STA) are associated with the El Niño?Southern Oscillation (ENSO) variability in the tropical Pacific. SSTAs over the STA are associated with the quasi-biennial component of ENSO with a timescale of 22?32 months, and SSTAs over the NTA are influenced by the low-frequency part of the ENSO signal with a timescale of 36?48 months. The ENSO influence is seasonally dependent. The strongest linkages occur in the spring of each hemisphere. In addition to ENSO, SSTAs in the north equatorial Atlantic are also modulated by the circulation and net heat flux anomalies associated with the North Atlantic oscillation (NAO). The atmospheric impact on the ocean is different in the STA and NTA regions. When the quasi-biennial signal is strong in the central Pacific during September?November, warm SSTAs excite the Pacific South American wave train extending from the Pacific to the South Atlantic. The associated wind-driven dynamics initiates the changes in the STA. The local net heat flux anomalies and ocean wave dynamics influence the location and the strength of the SSTA maximum. The SSTAs over the NTA region are driven by the local heat flux anomalies related to the trade wind changes associated with the low-frequency component of ENSO in the Pacific. The magnitudes of SSTAs depend on the phase of the NAO. The net heat flux anomalies associated with the NAO may enhance or diminish the impact of ENSO over the NTA region and modulate SSTAs in the North Atlantic.