Tropical–North Pacific Climate Linkages over the Past Four Centuries*

Abstract

Analyses of instrumental data demonstrate robust linkages between decadal-scale North Pacific and tropical Indo-Pacific climatic variability. These linkages encompass common regime shifts, including the noteworthy 1976 transition in Pacific climate. However, information on Pacific decadal variability and the tropical high-latitude climate connection is limited prior to the twentieth century. Herein tree-ring analysis is employed to extend the understanding of North Pacific climatic variability and related tropical linkages over the past four centuries. To this end, a tree-ring reconstruction of the December-May North Pacific index (NPI)-an index of the atmospheric circulation related to the Aleutian low pressure cell-is presented (1600-1983). The NPI reconstruction shows evidence for the three regime shifts seen in the instrumental NPI data, and for seven events in prior centuries. It correlates significantly with both instrumental tropical climate indices and a coral-based reconstruction of an optimal tropical Indo-Pacific climate index, supporting evidence for a tropical-North Pacific link extending as far west as the western Indian Ocean. The coral-based reconstruction shows the twentieth-century regime shifts evident in the instrumental NPI and instrumental tropical Indo-Pacific climate index, and three previous shifts. Changes in the strength of correlation between the reconstructions over time, and the different identified shifts in both series prior to the twentieth century, suggest a varying tropical influence on North Pacific climate, with greater influence in the twentieth century. One likely mechanism is the low-frequency variability of the El Niño-Southern Oscillation (ENSO) and its varying impact on Indo-Pacific climate.

Synoptic scale controls on the δ18O in precipitation across Beringia

“…This dipole-like pattern corresponds to the mapped GNIP δ 18 O precip anomalies (Figures 2a and 2b). The 100 year δ 18 O diatom record from Heart Lake is also consistent with other NPIinferred paleorecords from across Beringia, including northwest North American tree ring records (r = 0.66, P < 0.001) [D'Arrigo et al, 2005], Na + concentrations in Mount Logan ice (r = À0.45, P < 0.001) [Osterberg et al, 2014], and the weight abundance of BSi in Heart Lake (r = À0.48, P < 0.01) [Krawiec and Kaufman, 2014].…”

Atmospheric controls on northeast Pacific temperature variability and change, 1900–2012

“…Based on the strong, physically realistic correlation between large-scale SLP and SST indices from 1900 to 2012, we conclude that dynamical forcing accounts for virtually all of the observed warming in NE Pacific Arc SST over the 1900-2012 period as well. Tree-ring proxies of the PDO pattern and NE Pacific coastal SST also display evidence of century-long trends during the last several hundred years (43)(44)(45)(46). Further study may clarify the mechanisms behind the low-frequency circulation-temperature variability of the NE Pacific, so that a fuller understanding of natural and anthropogenic changes can be attained.…”

Cycles and shifts: 1,300 years of multi-decadal temperature variability in the Gulf of Alaska

“…This may partly result from: (1) the varying spatial coverage of tree-ring data used for these PDO reconstructions; (2) the fact that the models are all calibrated during the recent period using teleconnected relationships that may not be time-stable, and/or; (3) possible modulation of local climate from El Niñ oSouthern Oscillation (ENSO) and volcanic events (D'Arrigo and Wilson 2006) or other non-stationarities in the growth-climate response. However, the early lack of agreement among the PDO reconstructions may also reflect a real pattern of less coherency in the Pacific atmosphere-ocean system prior to the twentieth century (Gedalof et al 2002;D'Arrigo et al 2005). It should be noted, however, that a recent analysis of most of the available PDO reconstructions (Verdon and Franks 2006) indicates similar timings in regime Fig.…”

“…Instrumental records are not long enough to place these twentieth century changes in a longer-term context and therefore a true understanding of the temporal and spatial modes of these synoptic features is not possible from these data alone. However, annually resolved proxy archives like tree-rings and corals have been successfully used to reconstruct synoptic indices of Pacific Decadal Variability (Linsley et al 2000;Biondi et al 2001;D'Arrigo et al 2001;Gedalof and Smith 2001;Gedalof et al 2002;D'Arrigo et al 2005;. From the growing database of these proxies, it may soon be possible to make specific inferences about past decadal variability and its forcing mechanisms.…”