The Pacific Decadal Oscillation was recently making news for a peculiar climate trend in Alaska. How the Pacific Decadal Oscillation (PDO) is different from EL Nino Southern Oscillation (ENSO)?
1. While PDO refers to abnormal cooling of the Ocean water in Northern Pacific Ocean, ENSO refers to abnormal warming of the waters of Northern Pacific Ocean
2. PDO is a short term phenomenon, ENSO is a long term Phenomenon
Choose the correct option from the codes given below:

Answer: [D] Both 1 & 2 are incorrect

The “Pacific Decadal Oscillation” (PDO) is a long-lived El Nino-like pattern of Pacific climate variability. We need to differentiate between PDO and ENSO:

  • Both PDO and ENSO have similar spatial climate fingerprints yet the major difference is that PDO persists for 20-30 years while the typical ENSO persists for 6 to 18
  • The primary climatic fingerprints of the PDO are most visible in the North Pacific/North American sector, while secondary signatures exist in the tropics. On the contrary, the primary climatic fingerprints of the

ENSO are visible in tropics while secondary are visible in North Pacific/North American sector.

The PDO has two cycles, viz. Cold Cycle and Warm Cycle, very much similar to La Nina and EI Nino of the ENSO cycle.

Major changes in northeast Pacific marine ecosystems have been correlated with phase changes in the PDO; warm eras have seen enhanced coastal ocean biological productivity in Alaska and inhibited productivity off the west coast of the contiguous United States, while cold PDO eras have seen the opposite north-south pattern of marine ecosystem productivity.


PDO is under studies. Causes for the PDO are not currently known. Potential predictability for this climate oscillation are also not known.


The PDO has a major influence on Alaskan and for those matter global temperatures. The positive phase favors more EI Ninos and a stronger Aleutian low and warm water in the north Pacific off the Alaskan coast. The negative phase more La Ninas and cold eastern Gulf of Alaska waters. Note the strong similarity of the positive phase with EI Nino and the negative with La Nina.

PDO is responsible for bringing colder surface water temperatures and thus beginning the overall cooling effect in recent times in Alaska. This oscillation has brought a weakening of the ‘Aleutian Low’, the breeding ground for storms that end up regulating weather systems in the rest of the 48 states. With a less active Aleutian Low, cold winter storms have been sticking around Alaska longer and keeping the temperatures chilly.

This question is a part of GKToday's Integrated IAS General Studies Module