Quick
Search: 		  
advanced search
 GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help 
Geology Signup for GSW Email News
JOURNAL HOME HELP CONTACT PUBLISHER SUBSCRIBE ARCHIVE SEARCH TABLE OF CONTENTS
Geology; June 2009; v. 37; no. 6; p. 527-530; DOI: 10.1130/G25581A.1
© 2009 Geological Society of America
This Article
Right arrow Abstract
Right arrow Figures Only
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Felis, T.
Right arrow Articles by Kawahata, H.
Right arrow Search for Related Content
GeoRef
Right arrow GeoRef Citation

Subtropical coral reveals abrupt early-twentieth-century freshening in the western North Pacific Ocean

Thomas Felis1,*, Atsushi Suzuki2, Henning Kuhnert1, Mihai Dima3,4, Gerrit Lohmann3 and Hodaka Kawahata2,5,6

1 MARUM–Center for Marine Environmental Sciences, University of Bremen, 28359 Bremen, Germany
2 Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8567, Japan
3 Alfred Wegener Institute for Polar and Marine Research, 27570 Bremerhaven, Germany
4 Department of Atmospheric Physics, Faculty of Physics, University of Bucharest, 77125 Bucharest, Romania
5 Graduate School of Frontier Sciences, University of Tokyo, Tokyo 164-8639, Japan
6 Ocean Research Institute, University of Tokyo, Tokyo 164-8639, Japan

Correspondence: *E-mail: tfelis{at}uni-bremen.de


   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 MATERIAL AND METHODS
 RESULTS
 DISCUSSION
 CONCLUSIONS
 REFERENCES CITED
 
Instrumental climate observations provide robust records of global land and ocean temperatures during the twentieth century. Unlike for temperature, continuous salinity observations in the surface ocean are scarce prior to 1970, and the magnitude of salinity changes during the twentieth century is largely unknown. Surface ocean salinity is a major component in climate dynamics, as it influences ocean circulation and water mass formation. Here we present an annually resolved reconstruction of salinity variations in the surface waters of the western subtropical North Pacific Ocean since 1873, based on bimonthly records of {delta}18O, Sr/Ca, and U/Ca in a coral from the Ogasawara Islands. The reconstruction indicates that an abrupt regime shift toward fresher surface ocean conditions occurred between 1905 and 1910. Observational atmospheric data suggest that the abrupt freshening was associated with a weakening of the winds that drive the Kuroshio Current system and the associated subtropical gyre circulation. We note that the abrupt early-twentieth-century freshening in the western subtropical North Pacific precedes abrupt climate change in the northern North Atlantic by a few years. The potential for abrupt regime shifts in surface ocean salinity should be considered in climate predictions for the coming decades.


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
MATERIAL AND METHODS
 RESULTS
 DISCUSSION
 CONCLUSIONS
 REFERENCES CITED
 
Changes in surface ocean salinity and their role in influencing ocean circulation, water mass formation, and global climate are currently being widely discussed. However, assessing the range of salinity changes in the past is crucial for improved estimates on future climate based on model simulations. In the North Pacific Ocean, little is known about the range of surface ocean salinity variations throughout the twentieth century, due to a lack of continuous instrumental observations and appropriate proxy records.

The Kuroshio Current system is an important component of Earth's climate system. The northward-flowing Kuroshio, the western boundary current of the wind-driven North Pacific subtropical gyre, transports warm and saline tropical waters to higher latitudes (Fig. 1A). After leaving the Japanese coast it flows eastward as the Kuroshio Extension. A recirculation gyre exists to the south of the Kuroshio and its extension. In this region of the Pacific, where cold dry air masses from continental Asia encounter the warm Kuroshio waters, the ocean to atmosphere heat flux is among the highest in the world (KESS, 2008; Qiu, 2002; Yasuda, 2003). Here we present a reconstruction of sea-surface salinity (SSS) since 1873 from an annually banded coral growing in the western subtropical North Pacific, within the Kuroshio Current system.


Figure 01
View larger version (52K):
[in this window]
[in a new window]

  		Figure 1. Map of the North Pacific Ocean and bimonthly {delta}18O, Sr/Ca, and U/Ca records from a western subtropical North Pacific coral. A: Sea-surface salinity map (Conkright et al., 2002). The coral site in the Ogasawara Islands and schematic flow patterns of Kuroshio, Kuroshio Extension, and Kuroshio recirculation are shown (Imawaki et al., 2001; Taneda et al., 2000). B: Coral {delta}18O, Sr/Ca, and U/Ca records. Gray bar—time interval 1905–1910.

 

   MATERIAL AND METHODS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIAL AND METHODS
RESULTS
 DISCUSSION
 CONCLUSIONS
 REFERENCES CITED
 
A core was drilled in 2002 through a living Porites coral at Chichijima, Ogasawara Islands (Japan), located in the southwestward return flow of the Kuroshio recirculation system (Taneda et al., 2000). The massive colony, growing at 5.6 m water depth on the island's northern side (27° 6.355' N, 142° 11.645' E), is directly exposed to open-ocean conditions. The bimonthly resolved records of {delta}18O, Sr/Ca, and U/Ca generated from the aragonitic coral skeleton show clear annual cycles that can be counted back to the year 1873 (Fig. 1B) (for detailed methods see GSA Data Repository1). This age model is corroborated by the skeletal pattern of annual density-band pairs as revealed by X-radiographs (Fig. DR1 in the GSA Data Repository). The annual cycles in coral {delta}18O, Sr/Ca, and U/Ca reflect the sea-surface temperature (SST) seasonality, which has an amplitude of 7 °C at Chichijima.


   RESULTS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIAL AND METHODS
 RESULTS
DISCUSSION
 CONCLUSIONS
 REFERENCES CITED
 
The most striking feature of the coral {delta}18O record is a prominent shift toward more negative values in the early twentieth century (Fig. 1B). Because coral {delta}18O reflects both temperature and {delta}18O of seawater, this shift could indicate a change toward warmer and/or fresher conditions. The corresponding coral Sr/Ca and U/Ca paleothermometer records, however, do not reveal simultaneous warming. The annual average coral Sr/Ca and U/Ca records are in excellent agreement with each other and are highly correlated with a 20-year instrumental SST record from Chichijima (Fig. 2). We reconstructed SST from coral Sr/Ca and U/Ca, which allowed us to subtract the temperature component from coral {delta}18O. We generated two annually resolved salinity reconstructions by combining the annual average coral {delta}18O record with the Sr/Ca and U/Ca records, respectively. The residual coral {delta}18O ({Delta}{delta}18O) reflects variations in {delta}18Oseawater, which are closely related to salinity changes. The two annually resolved coral {Delta}{delta}18O records are in excellent agreement with each other and are highly correlated with regional SSS based on reanalysis data (SODA 1.4.2) (Carton and Giese, 2008), giving confidence in their application as SSS proxy. Furthermore, our results suggest that U/Ca in this coral is a robust paleothermometer and not influenced by salinity variations.


Figure 02
View larger version (42K):
[in this window]
[in a new window]

  		Figure 2. Interannual records of Sr/Ca, U/Ca, {delta}18O, and paleosalinity from a western subtropical North Pacific coral. Instrumental SST and SSS axes are visually scaled. Thin lines—annual records and corresponding error bars; bold lines—three-year running averages; gray bar—time interval 1905–1910. A: Coral Sr/Ca and U/Ca records, and local sea-surface temperature (SST) (Tokyo Metropolitan Ogasawara Fisheries Center). B: Coral {delta}18O record. C: Residual coral {delta}18O records ({Delta}{delta}18O) based on {delta}18O and Sr/Ca, and {delta}18O and U/Ca; coral-based sea surface salinity (SSS) anomaly calculated from regional {delta}18Oseawater-salinity relationship (0.42{per thousand} per 1 psu) (Schmidt et al., 1999); and regional SSS from Simple Ocean Data Assimilation (SODA) reanalysis (Carton and Giese, 2008) (27.0°–27.5° N, 142.0°–142.5° E). D: Northeast Asia winter (December, January, February) sea-level pressure (SLP) (45°–60° N, 110°–130° E) (Basnett and Parker, 1997). E: Fram Strait sea-ice export reconstruction (Schmith and Hansen, 2003).

 
Coral physiology, calcification rate, and diagenesis can be excluded as causes of the early-twentieth-century shift toward more negative coral {delta}18O. The Ogasawara coral {Delta}{delta}18OSr/Ca and {Delta}{delta}18OU/Ca records are therefore interpreted to indicate an abrupt freshening of the surface waters in the western subtropical North Pacific between 1905 and 1910, which has the character of a regime shift. The average of the two paleosalinity records indicates that this freshening was associated with a 0.345 ± 0.005{per thousand} decrease in seawater {delta}18OVPDB. Using the relationship of 0.433{per thousand} {delta}18OVSMOW per 1 psu (0.420{per thousand} {delta}18OVPDB per 1 psu) for this region of the Pacific (24.5°–35° N, 140°–171° E; 0–50 m water depth) (Schmidt et al., 1999), this would translate into a 0.82 ± 0.01 psu decrease in SSS. The analytical uncertainty for annual average coral {Delta}{delta}18O is ±0.038{per thousand} or ±0.09 psu. The magnitude of the freshening is high but on the same order as interdecadal variations in South Pacific coral {delta}18Oseawater reconstructions (Calvo et al., 2007; Hendy et al., 2002; Linsley et al., 2006; Quinn et al., 2006) when translated into salinity. We note that the quantification of the freshening is dependent on the applied {delta}18Oseawater-salinity relationship. For instance, a 0.345 ± 0.005{per thousand} decrease in {delta}18Oseawater would translate into a 0.14 ± 0.02 psu decrease in SSS, based on the regression of coral {Delta}{delta}18O with regional SSS. However, the amplitude of regional SSS is dependent on the reanalysis procedure and data set version. A higher interannual variability in coral-based compared to SODA 1.4.2 salinity has also been observed at other locations (Cahyarini et al., 2008).


   DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 MATERIAL AND METHODS
 RESULTS
 DISCUSSION
CONCLUSIONS
 REFERENCES CITED
 
Potential causes of the abrupt 1905–1910 surface ocean freshening include changes in precipitation and atmospheric and oceanic circulation. Instrumental observations of Ogasawara precipitation started in 1907 (Vose et al., 1992). At the western margin of the Pacific, however, precipitation records from Okinawa (26.2° N) and Tokyo (35.8° N) extend back into the nineteenth century and show no evidence for an early-twentieth-century regime shift. We therefore exclude precipitation changes as a cause of the freshening.

The difference in average Northern Hemisphere sea-level pressure (SLP) fields (Basnett and Parker, 1997) between the periods after (1910–1942) and before the freshening (1873–1905) reveals maximum gradients over southern Japan, close to the Ogasawara Islands (Fig. 3). This spatial and temporal coincidence provides evidence that the reconstructed freshening is associated with a shift in the large-scale atmospheric circulation. The SLP anomalies indicate an anomalous anticyclonic circulation over northeast Asia most pronounced in winter, and an anomalous cyclonic circulation over the western subtropical North Pacific most prominent in summer (Fig. DR2). An anomalous easterly/northeasterly surface circulation over southern Japan is associated with this atmospheric pattern, which is physically consistent with a weakening of the prevailing westerlies/southwesterlies over the western subtropical to midlatitude North Pacific.


Figure 03
View larger version (35K):
[in this window]
[in a new window]

  		Figure 3. Sea-level pressure (SLP) difference between the periods after and before the 1905–1910 freshening. Average SLP (Basnett and Parker, 1997) for 1910–1942 minus that for 1873–1905 for annual average conditions. Climatological surface winds, which are weakened by the anomalous atmospheric circulation resulting from the SLP anomaly pattern that is characterized by maximum gradients over southern Japan, are schematically represented as white arrows. Units are hPa. White dot—Ogasawara Islands.

 
Since precipitation changes are not likely the cause of the freshening, this suggests changes in evaporation and/or water masses. Our findings are consistent with a weakening of the winds that drive the Kuroshio Current system and the associated subtropical gyre circulation. In this region of the North Pacific, wind stress forcing, Kuroshio transport, subtropical gyre intensity, and westward expansion of high-salinity waters are strongly coupled (Deser et al., 1999; Miller et al., 1998; Nakano et al., 2005; Qiu and Chen, 2005; Shuto, 1996; Suga et al., 2000; Yasuda and Hanawa, 1997). A weakened Kuroshio would result in decreased northward transport of warm saline water to subtropical latitudes. Weakened westerlies would, in addition to reducing Kuroshio transport, result in decreased advection of cold dry air from Asia, reducing evaporation over the ocean. The two mechanisms would affect regional SSS in the same sense, resulting in an amplified freshening signal, but would affect SST in the opposite sense. This is consistent with the only minor cooling accompanying the abrupt freshening (Fig. 2), probably reflecting the dominance of Kuroshio transport relative to continental air advection in controlling regional SST. High-salinity surface waters (>35 psu) are restricted today to the central subtropical North Pacific (Fig. 1A). Because a wind-driven weakening of the Kuroshio Current system is associated with an eastward contraction of these waters (Shuto, 1996; Suga et al., 2000), this mechanism could have further amplified the freshening in the western subtropical North Pacific. We conclude that the Ogasawara Islands represent a very sensitive location with respect to SSS changes, because the combination of atmospheric and oceanic advection processes results in a large-amplitude salinity signal.

Observational studies indicate a four- to five-year lag of the strength of the Kuroshio Extension and associated gyre-scale circulation relative to wind stress forcing (Deser et al., 1999). Consistent with these observations, the winter SLP record from the northeast Asian atmospheric anomaly center reveals that the 1905–1910 freshening lags an abrupt shift toward higher SLP (1901–1905) by approximately four years (Fig. 2). This suggests an important role for the northeast Asian atmospheric center in initiating the weakening of the winds that drive the Kuroshio Current system. In the subtropical atmospheric center, a corresponding shift toward lower summer SLP is more gradual (Fig. DR3). We note that the early-twentieth-century freshening shift is different from the overall interannual to decadal variability of our salinity reconstruction. This variability with significant variance at periods of two to six years (Fig. DR4) does not show strong similarity to northeast Asian SLP throughout most of the twentieth century, and is very likely controlled by other processes.

Pacific {delta}18Oseawater reconstructions resolving interannual to decadal variability are restricted to coral records (Calvo et al., 2007; Hendy et al., 2002; Linsley et al., 2006; Quinn et al., 2006). These Southern Hemisphere records reveal no early-twentieth-century freshening but a mid-nineteenth-century freshening of the tropical southwestern Pacific (Hendy et al., 2002). However, a causal link between the latter and our subtropical northwestern Pacific freshening is speculative. The coral {delta}18O record closest to the Ogasawara Islands, from tropical Guam (13° N, 145° E) (Asami et al., 2005), apparently indicates no early-twentieth-century freshening. We conclude that the latter reflects a phenomenon restricted to the subtropical North Pacific.

Evidence for early-twentieth-century abrupt climate change is rare in the North Pacific. A 1905 regime shift is observed in a Pacific Decadal Oscillation (PDO) reconstruction (Gedalof et al., 2002) that combines tropical and extratropical archives (Fig. DR5). The relevance of this finding has been neglected so far, mostly because the instrumental PDO index (Mantua et al., 1997), solely based on extratropical North Pacific SST, does not reveal a corresponding shift. The occurrence of a regime shift ca. 1905 in reconstructions of the PDO (Gedalof et al., 2002) and SSS in the Kuroshio recirculation is consistent with the hypothesis that the PDO arises from superposition of phenomena of tropical and North Pacific origin, including oceanic advection in the Kuroshio Extension (Schneider and Cornuelle, 2005). In the western United States, a region strongly influenced by North Pacific climate (Mantua et al., 1997), a period of persistent wet conditions started in 1905 (Woodhouse et al., 2005). This pluvial period lasted until 1917. The reconstructions of western subtropical North Pacific salinity, PDO, and western U.S. rainfall do not correlate otherwise, but a 1905 regime shift is common to all of them. This demonstrates the large-scale nature of this shift, which is superimposed on regional climate variability.

More evidence for early-twentieth-century abrupt climate change comes from the northern North Atlantic. A regime shift toward lower Fram Strait sea-ice export from the Arctic Ocean occurred between ca. 1909 and 1914 (Schmith and Hansen, 2003), lagging our western subtropical North Pacific freshening by a few years (Fig. 2). The freshwater export through Fram Strait is thought to influence the Atlantic thermohaline circulation (Dima and Lohmann, 2007; Schmith and Hansen, 2003). A physical mechanism linking the two abrupt early-twentieth-century regime shifts could involve (1) North Pacific atmosphere-ocean interactions affecting Fram Strait sea-ice export via atmospheric teleconnections (Dima and Lohmann, 2007), and/or (2) changes in transport of North Pacific water to the North Atlantic through Bering Strait (Keigwin and Cook, 2007).

The 1995–2002 interval of the coral record was not interpreted. Although all proxies show clear annual cycles during this interval, the annual average Sr/Ca and U/Ca indicate anomalously low SST, which is in conflict with anomalously high observed SST (Figs. DR6 and DR7). We speculate that this paleothermometer breakdown is due to thermal stress (Marshall and McCulloch, 2002), which is supported by local evidence for coral bleaching during this period.


   CONCLUSIONS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIAL AND METHODS
 RESULTS
 DISCUSSION
 CONCLUSIONS
REFERENCES CITED
 
Our results indicate an abrupt regime shift toward fresher surface ocean conditions between 1905 and 1910 in the western subtropical North Pacific, resulting from a combination of atmospheric and oceanic advection processes. Further investigations should address the potential triggers for this shift. We note that the early twentieth century is characterized by a rise in global temperatures (Brohan et al., 2006) and a minimum in the Gleissberg cycle of solar activity (Peristykh and Damon, 2003). Whether our regime shift is a consequence of anthropogenic or natural climate change or a combination of both remains to be shown.


   ACKNOWLEDGMENTS
 
We thank T. Sato and H. Adachi for core drilling, S. Tsukamoto (Tokyo Metropolitan University) for logistic support, M. Segl (University of Bremen) for stable isotope analyses, Tokyo Metropolitan Ogasawara Fisheries Center for temperature data, and T. Schmith, C.A. Woodhouse, and Z. Gedalof for proxy data. R. Schlitzer's Ocean Data View was used to generate Figure 1A. Supported by Deutsche Forschungsgemeinschaft through DFG Research Center/Cluster of Excellence "The Ocean in the Earth System" (Felis, Kuhnert, Lohmann), Ministry of the Environment, Japan (Suzuki, Kawahata), and Alexander von Humboldt Foundation (Dima). Data are available via www.wdc-mare.org and www.ncdc.noaa.gov/paleo.


   FOOTNOTES
 
GSA Data Repository item 2009123, Figures DR1–DR10 (X-radiographs, spectral analysis results, thin-section photomicrographs, scanning electron micoscope images, and results from the 1995–2002 interval of coral record), material and methods, and supporting text, is available online at www.geosociety.org/pubs/ft2009.htm, or on request from editing{at}geosociety.org or Documents Secretary, GSA, P.O. Box 9140, Boulder, CO 80301, USA. Back


   REFERENCES CITED
TOP
 ABSTRACT
 INTRODUCTION
 MATERIAL AND METHODS
 RESULTS
 DISCUSSION
 CONCLUSIONS
 REFERENCES CITED
 

Asami, R., Yamada, T., Iryu, Y., Quinn, T.M., Meyer, C.P., and Paulay, G. 2005, Interannual and decadal variability of the western Pacific sea surface condition for the years 1787–2000: Reconstruction based on stable isotope record from a Guam coral: Journal of Geophysical Research, v. 110, C05018, doi: 10.1029/2004JC002555.[CrossRef]

Basnett, T.A., and Parker, D.E. 1997, Development of the Global Mean Sea Level Pressure Data Set GMSLP2: Hadley Centre Climate Research Technical Note CRTN 79: Bracknell, UK Hadley Centre, Meteorological Office 16 p. plus appendices.

Brohan, P., Kennedy, J.J., Harris, I., Tett, S.F.B., and Jones, P.D. 2006, Uncertainty estimates in regional and global observed temperature changes: A new data set from 1850: Journal of Geophysical Research, v. 111, D12106, doi: 10.1029/2005JD006548.[CrossRef]

Cahyarini, S.Y., Pfeiffer, M., Timm, O., Dullo, W.-C., and Garbe-Schönberg, D. 2008, Reconstructing seawater {delta}18O from paired coral {delta}18O and Sr/Ca ratios: Methods, error analysis and problems, with examples from Tahiti (French Polynesia) and Timor (Indonesia): Geochimica et Cosmochimica Acta, v. 72, p. 2841– 2853, doi: 10.1016/j.gca.2008.04.005.[CrossRef][Web of Science][GeoRef]

Calvo, E., Marshall, J.F., Pelejero, C., McCulloch, M.T., Gagan, M.K., and Lough, J.M. 2007, Interdecadal climate variability in the Coral Sea since 1708 A.D: Palaeogeography, Palaeoclimatology, Palaeoecology, v. 248, p. 190– 201, doi: 10.1016/j.palaeo.2006.12.003.[CrossRef][GeoRef]

Carton, J.A., and Giese, B.S. 2008, A reanalysis of ocean climate using Simple Ocean Data Assimilation (SODA): Monthly Weather Review, v. 136, p. 2999– 3017, doi: 10.1175/2007MWR1978.1.[CrossRef][Web of Science]

Conkright, M.E., Locarnini, R.A., Garcia, H.E., O'Brien, T.D., Boyer, T.P., Stephens, C., and Antonov, J.I. 2002, World ocean atlas 2001: Objective analyses, data statistics, and figures, CD-ROM documentation: Silver Spring, Maryland National Oceanographic Data Center p. 17.

Deser, C., Alexander, M.A., and Timlin, M.S. 1999, Evidence for a wind-driven intensification of the Kuroshio Current extension from the 1970s to the 1980s: Journal of Climate, v. 12, p. 1697– 1706, doi: 10.1175/1520-0442(1999)012<1697:EFAWDI>2.0.CO;2.[CrossRef][Web of Science]

Dima, M., and Lohmann, G. 2007, A hemispheric mechanism for the Atlantic multidecadal oscillation: Journal of Climate, v. 20, p. 2706– 2719, doi: 10.1175/JCLI4174.1.[CrossRef][Web of Science]

Gedalof, Z., Mantua, N.J., and Peterson, D.L. 2002, A multi-century perspective of variability in the Pacific Decadal Oscillation: New insights from tree rings and corals: Geophysical Research Letters, v. 29, 2204, doi: 10.1029/2002GL015824.[CrossRef]

Hendy, E.J., Gagan, M.K., Alibert, C.A., McCulloch, M.T., Lough, J.M., and Isdale, P.J. 2002, Abrupt decrease in tropical Pacific sea surface salinity at the end of the Little Ice Age: Science, v. 295, p. 1511– 1514, doi: 10.1126/science.1067693.[Abstract/Free Full Text]

Imawaki, S., Uchida, H., Ichikawa, H., Fukasawa, M., Umatani, S., and Group, A. 2001, Satellite altimeter monitoring the Kuroshio transport south of Japan: Geophysical Research Letters, v. 28, p. 17– 20, doi: 10.1029/2000GL011796.[CrossRef][Web of Science]

Keigwin, L.D., and Cook, M.S. 2007, A role for North Pacific salinity in stabilizing North Atlantic climate: Paleoceanography, v. 22, PA3102, doi: 10.1029/2007PA001420.[CrossRef]

KESS (Kuroshio Extension System Study) 2008, Collaborative research project proposal: http://uskess.org/pdfs/kessAll.pdf (January 2009).

Linsley, B.K., Kaplan, A., Gouriou, Y., Salinger, J., deMenocal, P.B., Wellington, G.M., and Howe, S.S. 2006, Tracking the extent of the South Pacific Convergence Zone since the early 1600s: Geochemistry, Geophysics, Geosystems, v. 7, Q05003, doi: 10.1029/2005GC001115.[CrossRef]

Mantua, N.J., Hare, S.R., Zhang, Y., Wallace, J.M., and Francis, R.C. 1997, A Pacific interdecadal climate oscillation with impacts on salmon production: Bulletin of the American Meteorological Society, v. 78, p. 1069– 1079, doi: 10.1175/1520-0477(1997)078<1069:APICOW>2.0.CO;2.[CrossRef][Web of Science]

Marshall, J.F., and McCulloch, M.T. 2002, An assessment of the Sr/Ca ratio in shallow water hermatypic corals as a proxy for sea surface temperature: Geochimica et Cosmochimica Acta, v. 66, p. 3263– 3280, doi: 10.1016/S0016-7037(02)00926-2.[CrossRef][Web of Science][GeoRef]

Miller, A.J., Cayan, D.R., and White, W.B. 1998, A westward-intensified decadal change in the North Pacific thermocline and gyre-scale circulation: Journal of Climate, v. 11, p. 3112– 3127, doi: 10.1175/1520-0442(1998)011<3112:AWIDCI>2.0.CO;2.[CrossRef][Web of Science]

Nakano, T., Kaneko, I., Endoh, M., and Kamachi, M. 2005, Interannual and decadal variabilities of NPIW salinity minimum core observed along JMA's hydrographic repeat sections: Journal of Oceanography, v. 61, p. 681– 697, doi: 10.1007/s10872-005-0076-5.[CrossRef][Web of Science]

Peristykh, A.N., and Damon, P.E. 2003, Persistence of the Gleissberg 88-year solar cycle over the last ~12,000 years: Evidence from cosmogenic isotopes: Journal of Geophysical Research, v. 108, 1003, doi: 10.1029/2002JA009390.[CrossRef]

Qiu, B. 2002, The Kuroshio Extension system: Its large-scale variability and role in the midlatitude ocean-atmosphere interaction: Journal of Oceanography, v. 58, p. 57– 75, doi: 10.1023/A:1015824717293.[CrossRef][Web of Science]

Qiu, B., and Chen, S. 2005, Variability of the Kuroshio Extension jet, recirculation gyre, and mesoscale eddies on decadal time scales: Journal of Physical Oceanography, v. 35, p. 2090– 2103, doi: 10.1175/JPO2807.1.[CrossRef][Web of Science]

Quinn, T.M., Taylor, F.W., and Crowley, T.J. 2006, Coral-based climate variability in the Western Pacific Warm Pool since 1867: Journal of Geophysical Research, v. 111, C11006, doi: 10.1029/2005JC003243.[CrossRef]

Schmidt, G.A., Bigg, G.R., and Rohling, E.J. 1999, Global seawater oxygen-18 database: http://data.giss.nasa.gov/o18data/ (January 2009).

Schmith, T., and Hansen, C. 2003, Fram Strait ice export during the nineteenth and twentieth centuries reconstructed from a multiyear sea ice index from southwestern Greenland: Journal of Climate, v. 16, p. 2782– 2791, doi: 10.1175/1520-0442(2003)016<2782:FSIEDT>2.0.CO;2.[CrossRef][Web of Science][GeoRef]

Schneider, N., and Cornuelle, B.D. 2005, The forcing of the Pacific decadal oscillation: Journal of Climate, v. 18, p. 4355– 4373, doi: 10.1175/JCLI3527.1.[CrossRef][Web of Science]

Shuto, K. 1996, Interannual variations of water temperature and salinity along the 137°E meridian: Journal of Oceanography, v. 52, p. 575– 595, doi: 10.1007/BF02238322.[CrossRef]

Suga, T., Kato, A., and Hanawa, K. 2000, North Pacific tropical water: Its climatology and temporal changes associated with the climate regime shift in the 1970s: Progress in Oceanography, v. 47, p. 223– 256, doi: 10.1016/S0079-6611(00)00037-9.[CrossRef][Web of Science]

Taneda, T., Suga, T., and Hanawa, K. 2000, Subtropical mode water variation in the northwestern part of the North Pacific subtropical gyre: Journal of Geophysical Research, v. 105, p. 19,591– 19,598, doi: 10.1029/2000JC900073.[CrossRef]

Vose, R.S., Schmoyer, R.L., Steurer, P.M., Peterson, T.C., Heim, R., Karl, T.R., and Eischeid, J. 1992, The Global Historical Climatology Network: Long-term monthly temperature, precipitation, sea level pressure, and station pressure data, ORNL/CDIAC-53, NDP-041: Oak Ridge, Tennessee Oak Ridge National Laboratory, Carbon Dioxide Information Analysis Center 99 p. plus appendices.

Woodhouse, C.A., Kunkel, K.E., Easterling, D.R., and Cook, E.R. 2005, The twentieth-century pluvial in the western United States: Geophysical Research Letters, v. 32, L07701, doi: 10.1029/2005GL022413.[CrossRef]

Yasuda, I. 2003, Hydrographic structure and variability in the Kuroshio-Oyashio transition area: Journal of Oceanography, v. 59, p. 389– 402, doi: 10.1023/A:1025580313836.[CrossRef][Web of Science]

Yasuda, T., and Hanawa, K. 1997, Decadal changes in the mode waters in the mid-latitude North Pacific: Journal of Physical Oceanography, v. 27, p. 858– 870, doi: 10.1175/1520-0485(1997)027<0858:DCITMW>2.0.CO;2.[CrossRef][Web of Science]

Received for publication 6 October 2008

Revised manuscript received 23 January 2009

Manuscript accepted 29 January 2009





This Article
Right arrow Abstract
Right arrow Figures Only
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Felis, T.
Right arrow Articles by Kawahata, H.
Right arrow Search for Related Content
GeoRef
Right arrow GeoRef Citation

JOURNAL HOME HELP CONTACT PUBLISHER SUBSCRIBE ARCHIVE SEARCH TABLE OF CONTENTS
Copyright © 2010 by Geological Society of America