Decadal Variations in Western Pacific Warm Pool Dynamics as Evidenced by Porites Corals from Chuuk Atoll, FSM PDF Download

Author: Jennifer L. Massoll
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ISBN:
Category : Climatic changes
Languages : en
Pages : 50

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Author: Christopher Robert Maupin
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ISBN:
Category :
Languages : en
Pages : 382

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Observations and reconstructions of climate variability are necessary to place predictions of future global climate change into temporal context (Goddard et al., 2012). I focus here on the western tropical Pacific (Solomon Islands; ~9.5°S, ~160°E), a region directly influenced by: the South Pacific Convergence Zone (SPCZ), the West Pacific Warm Pool, the Pacific Walker Circulation, and the Hadley Circulation. The West Pacific Warm Pool (WPWP) is an integral source of heat and moisture to the atmosphere. It is part of both Walker and Hadley circulations, and the El Niño-Southern Oscillation (ENSO), which is the largest source of interannual climate variability on Earth. Modern observations of changes in the mean state of the WPWP, Walker circulation, and ENSO are limited in temporal scale and overprinted with the signal of anthropogenic climate change; hence, proxy-based observations in the pre-instrumental period are needed to place any future changes in these systems, and attribution of these changes, into context. I present evidence for large (~1.5 m), abrupt, and periodic changes in total annual rainfall amount on decadal to multidecadal timescales since 1423±5 CE (Year Common Era) in the Solomon Islands utilizing a fast growing (>2 mm yr−1) stalagmite sample and an empirical relationship developed between stalagmite [delta]18O and local rainfall amount. The ~600-yr Solomon Islands stalagmite [delta]18O record indicates that decadal oscillations in rainfall are a persistent characteristic of SPCZ-related climate variability, and available evidence points to these changes arising from internal forcing. Such changes have important implications to water resource management in this region, in addition to contextualizing models and future predictions of rainfall amount changes and latent heat release into the atmosphere via anthropogenic climate change. I also present a reconstruction pre-instrumental variability utilizing a monthly [delta]18O time series generated series from the long lived, slow-growing coral species Diploastrea heliopora spanning 1716-2008 CE. The record demonstrates strong coherence with modern instrumental variability, and in addition, demonstrates variance in centennial-multicentury, decadal-multidecadal and interannual bands. Quantitative comparison of the interannual component of the record to instrumental ENSO indices, and application of the resulting metrics to previously undocumented, potentially extreme ENSO events occurring during the early eighteenth and nineteenth centuries. These extreme events are absent from existing multiproxy reconstructions due to temporal limitations of extant proxies that have the greatest ENSO sensitivity. The intensity of these events may rival or exceed the largest in the instrumental record. The record also contains significant but transient decadal to multidecadal variability. The coral record exhibits a trend toward isotopic depletion, implying significant changes in SST and/or SSS over the entirety of the record. I also document the unique behavior of the SPCZ and the Intertropical Convergence Zone (ITCZ) over the past six centuries, present evidence of influence by decadal-scale advection processes on Solomon Islands SSS, and explore basin-scale changes in the tropical Pacific conditions potentially related to global average temperature change over the past three centuries.

Author: Autumn Noel Kidwell
Publisher:
ISBN: 9781369128772
Category :
Languages : en
Pages :

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In recent years, it has been observed that there are different types of El Niño events. The warm events can be divided into two categories: those centered in the central Pacific (CP) and those centered in the eastern Pacific (EP). We examined the variability of western Pacific warm pool (WP) horizontal migration and size from January 1982 to December 2011 by applying Ensemble Empirical Mode Decomposition (EEMD) and Hilbert Huang Spectrum (HHS) to the optimally interpolated sea surface temperature (OISST) data set. The analysis shows that the long-term residual trend of the zonal centroid movement is migrating to the west by 3.78° from the mean location during the past 30 years. The size of the warm pool has also increased 18% during this period. These analysis techniques isolated two separate time series for the migration of the zonal component of the WPWP for both CP and EP events and showed that these two types of El Niño generally operate at different time-scales. The EP time-series shows the strong traditional EP El Niño and the transition between strong El Niño conditions and La Niña conditions. The CP time-series shows that CP El Niños occur more often than EP El Niños. The changes of the El Niño type in conjunction with westward drift and increasing warm pool size shows an interesting multidecadal change in the warm pool. To extend the centroid study, we also examine the role of the Western Pacific Warm Pool (WP) in the past thirty years of mixed interannual variability, decadal variability, and climate change. Our analysis method involves a multi-dimensional study of the vertical centroid migration, volume, and heat content of the WP and an application of the advanced time-series analysis technique known as Multidimensional Ensemble Empirical Mode Decomposition (MEEMD). We show the 30-year evolution of the warm pool and how it interacts with the PDO, ENSO, and anthropogenic climate forcing mechanisms. Our results show that the WP increasing in size and increasing in heat content anomaly in response to global warming forcing. The variability of the South Pacific Convergence Zone (SPCZ) is evaluated using ocean surface wind products derived from the ERA-Interim atmospheric reanalysis for the period of 1981-2014 and QuickSCAT satellite scatterometer for the period of 1999- 2009. From these products, indices were developed to represent the SPCZ strength, area, and centroid location. Excellent agreement is found between the indices derived from the two wind products during the QuikSCAT period in terms of the spatiotemporal structures of the SPCZ. The longer ERA-Interim product is used to study the variations of SPCZ properties on intraseasonal, seasonal, interannual, and decadal time scales. The SPCZ strength, area, and centroid latitude have a dominant seasonal cycle. In contrast, the SPCZ centroid longitude is dominated by intraseasonal variability due to MJO influence. The SPCZ indices are all correlated with El Niño-Southern Oscillation indices. Interannual and intraseasonal variations of SPCZ strength during strong El Niño are approximately twice as large as the respective seasonal variations. SPCZ strength depends more on the intensity of El Niño rather than the central vs. eastern-Pacific type. The change from positive to negative PDO around 1999 results in a westward shift of the SPCZ centroid longitude, much smaller interannual swing in centroid latitude, and a decrease in SPCZ area. This study improves the understanding of the variations of the SPCZ on multiple time scales and reveals the variations of SPCZ strength not reported previously. The diagnostics analyses can be used to evaluate climate models to gauge their fidelity. We have analyzed multiple data sets (wind, SST, heat content) in an effort to better understand the the WP and the SPCZ. As a major component of the tropical Pacific Ocean dynamics and global climate dynamics, these two intertwined components are critical to study. This is especially true in the context of global climate change.

Author:
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Category :
Languages : en
Pages : 5

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A source of instability in the western Pacific warm pool is shown to be due to sea surface elevation variations caused by changes in the zonal sea-surface temperature (SST) gradient and the changes in the Pacific Ocean basin length in relation to the warm pool latitudinal location. The variation of the sea-surface elevation is measured by using the thermocline depth response calculated from a two-layer ocean. The warm pool is shown to be barely at equilibrium during the boreal late winter and early spring by comparing the measured thermocline at 110°W, 0°E with the calculated thermocline depth. Based on this analysis, a failure or reversal of the climatological zonal winds are apparently not a necessary precursor for the instability of the warm pool and initiation of a warm event. A warm event can be initiated by an increase in the size of the warm pool and/or an increase in zonal SST differences during the boreal/winter spring. This mechanism could be an alternate mechanism for El-Nino Southern Oscillation (ENSO) dynamics to that postulated by Bjeknes (1969).

Author: Martina Hollstein
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Category :
Languages : en
Pages :

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Author: U.S. TOGA COARE Science Working Group
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ISBN:
Category : Atmospheric circulation
Languages : en
Pages : 152

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Author: Kristen Mitchell
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Category : Climatology
Languages : en
Pages : 49

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Author: 羅立
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Category :
Languages : en
Pages :

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Author: Tropical Ocean/Global Atmosphere Program
Publisher:
ISBN: 9780875907864
Category : Marine meteorology
Languages : en
Pages : 314

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Author: Christopher Matthew Kovalik
Publisher:
ISBN:
Category :
Languages : en
Pages : 128

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The full effects of climate change are still unknown, but the future of coral-reefs appears bleak. Recently, there have been major episodes of coral bleaching and coral disease around the world. The recent loss of coral has been extreme, but there is some precedent for coral-reef collapse in the geologic record; several millennial-scale hiatuses in reef growth have been found throughout the Pacific Ocean in the late Holocene. A ~2,500-year hiatus in reef growth was found at multiple sites in Pacific Panamá, Costa Rica, Australia and Hawaii, as well as several small-scale hiatuses in the northern Ryukyu Islands. I used push-coring to compare the Holocene histories of two sites on opposite sides of the Pacific Ocean to see if they experienced this same millennial-scale hiatus in reef growth. The first site was Coiba Island, Panamá. This site has some of the oldest and thickest reefs in the eastern Pacific, in part due to its relatively stable year-round sea-surface temperatures. Coiba is not affected by tropical cyclones, as they move westward across the Pacific. The second coring site was Kumejima, Japan. Kumejima is bathed by the warm waters of the Kuroshio Current. Kumejima is part of the Ryukyu Island Arc, which is highly exposed to storm activity, experiencing numerous tropical cyclones annually. The climatic conditions at each site were examined through wavelet analysis. Wavelet analysis of sea-surface temperature anomalies, using monthly data from 1870-2012, was undertaken for each site, highlighting the periodicity and timing of trends in anomalous temperatures. These records were then compared with each other using wavelet-coherence analysis. Wavelet-coherence analysis revealed correlations between the two wavelets, highlighting the periodicity and time period when these sites were experiencing similar anomalous temperatures. Using two different forms of wavelet coherence, it was shown that these sites experienced anomalous temperatures at the ENSO (El Niño/Southern Oscillation) timescale only periodically throughout the past century and a half. There was also visible correlation at the decadal timescale twice, likely reflecting the Pacific Decadal Oscillation. Wavelet analysis made shared climatic trends between these sites much easier to detect and also revealed that these two dissimilar sites are linked climatically. Using cores taken from coral-reef framework to assess coral growth of the past ~6000 cal BP (calibrated calendar years before 1950), a hiatus in reef growth was found from ~4290-2024 cal BP at Coiba. Even with some of the best conditions for coral growth in the eastern Pacific, Coiba Island also experienced this millennial-scale hiatus in reef growth. The hiatus found at Coiba occurred contemporaneously with the millennial-scale hiatuses in reef growth observed in other areas of Pacific Panamá. This hiatus in reef growth took place during a time of increased ENSO activity; a similar increase in ENSO activity is predicted under future climate-change conditions. Extreme El Niño and extreme La Niña events are predicted to increase with climate change, threatening the precious coral-reef ecosystem that is already sparse in the equatorial eastern Pacific. Nearly all corals in the cores analyzed from Kumejima were in very poor taphonomic condition and were comprised nearly entirely of Acropora spp. encrusted in coralline algae. Radiocarbon ages from the Kumejima cores revealed a mixed deposition. All dates collected from depths ranging from 30-235 cm below the surface were between the ages of 2966-3775 cal BP. All of these corals dated within the time frame of the hiatus observed in Panamá, showing that there was coral growth at Kumejima during this time. The dates obtained from coral from Kumejima were also during the short-term hiatus found at nearby Kodakarajima, in the Northern Ryukyus, meaning the hiatus at Kodakarajima was likely a localized event. Every coral dated from Kumejima was alive during the Pulleniatina Minimum Event (PME), which is believed to have resulted in the slowing of the Kuroshio Current. Any alteration in the flow of the Kuroshio could have altered reef growth at Kumejima: my record from this site may represent rubble deposits during this event. Both of these sites are largely controlled by oceanic-atmospheric processes taking place on a large scale. Reef dynamics at Coiba Island were likely controlled by ENSO activity, especially Eastern Pacific El Niño, and this site has low coral diversity. On the other hand, reef development at Kumejima is influenced by storm activity, mainly tropical cyclones, which, in both frequency and intensity, can be attributed to the same forces controlling ENSO activity in the eastern equatorial Pacific. With the current projections of climate change the oceanic waters will warm, storm intensity will increase, ENSO events will become more extreme, and patterns of precipitation will likely change. Similar changes have occurred in the past, driving corals beyond their threshold of survival. The prediction of a more El Niño-like conditions in the future could be disastrous for both Coiba and Kumejima. Coiba would face higher than normal temperatures whereas Kume would experience an increase in the intensity of typhoons. These reefs have been resilient to temperature changes in the past, with Panamanian reefs recovering from an over 2000 year hiatus; if we can slow or reverse the current rate of climate change in the immediate future, these reefs still may stand a chance to survive.