Hindcast of the 1976/77 and 1998/99 climate shifts in the Pacific

• Published in: Journal of Climate
• Main Authors: Ding, Hui, Greatbatch, Richard John, Latif, Mojib, Park, Wonsun, Gerdes, Rüdiger
• Format: Article in Journal/Newspaper
• Language: English
• Published: AMS (American Meteorological Society) 2013
• Subjects: Pacific; aleutian low; Sea ice
• Online Access: https://oceanrep.geomar.de/id/eprint/20815/; https://oceanrep.geomar.de/id/eprint/20815/1/jcli-d-12-00626.1-1.pdf; https://doi.org/10.1175/JCLI-D-12-00626.1

The use of a coupled ocean/atmosphere/sea-ice model to hindcast (i.e. historical forecast) recent climate variability is described and illustrated for the cases of the 1976/77 and 1998/99 climate shift events in the Pacific. The initialization is achieved by running the coupled model in partially coupled mode whereby global observed wind stress anomalies are used to drive the ocean/sea-ice component of the coupled model while maintaining the thermodynamic coupling between the ocean/sea-ice and atmosphere components. Here we show that hindcast experiments can successfully capture many features associated with the 1976/77 and 1998/99 climate shifts. For instance, hindcast experiments started from the beginning of 1976 can capture sea surface temperature (SST) warming in the central-eastern equatorial Pacific and the positive phase of the Pacific Decadal Oscillation (PDO) throughout the 9 years following the 1976/77 climate shift, including the deepening of the Aleutian low pressure system. Hindcast experiments started from the beginning of 1998 can also capture part of the anomalous conditions during the 4 years after the 1998/99 climate. We argue that the dynamical adjustment of heat content anomalies that are present in the initial conditions in the tropics is important for the successful hindcast of the two climate shifts.