Regime shifts in global SSTs

1
Regime shifts in global SSTs Yasunaka, S. and K.
Hanawa (Tohoku Univ., Japan) International
Journal of Climatology 25 913-930 (2005)

• Purposes
• To describe the spatio-temporal structure of the
  regime shifts in the global scale.
• To investigate the relationship between the ENSO
  events and the regime shifts.

• Detection of regime shifts

Ratio of the significantly changed grids to the
data-filled grids

• JFM Large ratios are detected at
• 1925/26, 1940s, 1957/58, 1970/71, 1976/77
• More than half of 9 individual oceans have large
  change.
• They can be regarded as global regime shifts.

2

• Relation to ENSO events

Time series of the Niño 3.4 index
JFM JAS
Regime shifts ENSO events ENSO events
concurrently occurring with the regime shifts

• The regime shifts occur concurrently with the
  ENSO events.
• The ENSO events with the regime shifts show
  characteristic seasonal evolutions.

• Seasonal evolution of the regime shifts is
  similar to that of the ENSO events.

• Relation to dominant variation modes
• EOF analysis ENSO, Southern Hem.
  trend, NP, AO modes
• Significant phase reversals in the ENSO, NP, and
  AO modes at the regime shifts

• Interaction between the regime shifts and the
  ENSO events
• The ENSO event would play as a
  trigger of the regime shift.
• The NP mode would suppress phase
  reversal of the ENSO event.