The formation of North Atlantic Deep Water (NADW) involves the transfer of upper-layer water to abyssal depths at a rate of 15 to 20 × 10^6 m^3/s. This process is crucial for the global thermohaline circulation, linking the main thermoclines of the ocean. The return flow of warm water, which is essential for maintaining the NADW production cycle, primarily occurs within the ocean's warm water thermocline layer. The warm water route, involving the Pacific to Indian Ocean flow through the Indonesian Seas, advection across the Indian Ocean, and southward transfer through the Mozambique Channel, is proposed as the primary pathway for the return flow. This route is more significant than the cold water route via the Drake Passage. The warm water route is characterized by strong vertical mixing, nutrient enrichment, and increased salinity and volume flux. The Agulhas Current, a key component of this route, can vary in its flow into the Atlantic, influenced by wind-driven circulation and the Southern Oscillation. The Indonesian Sea link, which includes the Pacific to Indian Ocean exchange, is also susceptible to variability on various time scales. The overall circulation pattern, including the warm water route and the Agulhas Current, plays a vital role in global heat and freshwater fluxes and may be affected by climate variability.The formation of North Atlantic Deep Water (NADW) involves the transfer of upper-layer water to abyssal depths at a rate of 15 to 20 × 10^6 m^3/s. This process is crucial for the global thermohaline circulation, linking the main thermoclines of the ocean. The return flow of warm water, which is essential for maintaining the NADW production cycle, primarily occurs within the ocean's warm water thermocline layer. The warm water route, involving the Pacific to Indian Ocean flow through the Indonesian Seas, advection across the Indian Ocean, and southward transfer through the Mozambique Channel, is proposed as the primary pathway for the return flow. This route is more significant than the cold water route via the Drake Passage. The warm water route is characterized by strong vertical mixing, nutrient enrichment, and increased salinity and volume flux. The Agulhas Current, a key component of this route, can vary in its flow into the Atlantic, influenced by wind-driven circulation and the Southern Oscillation. The Indonesian Sea link, which includes the Pacific to Indian Ocean exchange, is also susceptible to variability on various time scales. The overall circulation pattern, including the warm water route and the Agulhas Current, plays a vital role in global heat and freshwater fluxes and may be affected by climate variability.