Tracking the South Pacific convergence zone variability and recent acidification reconstructed from tropical corals

2021 ◽  
Author(s):  
Sara Todorović ◽  
Henry C. Wu ◽  
Braddock Linsley ◽  
Delphine Dissard ◽  
Henning Kuhnert ◽  
...  
Keyword(s):  
Southern Oscillation ◽  
Global Climate ◽  
South Pacific ◽  
South Pacific Convergence Zone ◽  
Convergence Zone ◽  
Climatic Fluctuations ◽  
Ph Variation ◽  
Enso Events ◽  
Strong Trend ◽  
Tropical Oceans

<p>Massive tropical corals represent one of the most important natural archives of modern climate change. Coral based reconstructions give us the possibility to extend the instrumental oceanographic records and observe hydrographic variability on seasonal to interdecadal scales in tropical oceans. South Pacific convergence zone (SPCZ) variability, Interdecadal Pacific Oscillation (IPO) and El Niño-Southern Oscillation (ENSO) events are major drivers of global climate and may exert control on regional CO<sub>2</sub> absorption, outgassing and pH variability.</p><p><em>Porites</em> sp. corals from Tonga and Rotuma (Fijian dependency) are being analyzed for multi-proxy (e.g. Sr/Ca, δ<sup>18</sup>O, δ<sup>13</sup>C, δ<sup>11</sup>B, B/Ca) reconstructions of sea surface temperature and salinity (SST, SSS) and carbonate chemistry, on a monthly to annual resolution. Preliminary data of the Rotuma <em>Porites</em> sp. coral shows δ<sup>18</sup>O has been decreasing by 0.004 ‰ per year at the end of the 20th century, suggesting freshening and/or warming of the surface water. In the same period, we observe a δ<sup>13</sup>C decrease of 0.017 ‰ per year in-line with the anthropogenic CO<sub>2</sub> driven Suess effect. Initial results of the δ<sup>11</sup>B Tonga <em>Porites</em> sp. show high interannual variability, and a strong trend of decrease of -0.0626 ‰ per year in the last five decades of the record (1949-2004) suggesting acidification. The results are in agreement with published coral-based reconstructions from the region.</p><p>When completed, the new records will facilitate exploring the effects of modern anthropogenic influence on ocean carbonate system and pH variation, and the relationship between them and interannual and decadal-interdecadal climatic fluctuations.</p>

scholarly journals Using Atmospheric Energy Transport to Quantitatively Constrain South Pacific Convergence Zone Shifts during ENSO

2019 ◽  
Vol 32 (6) ◽  
pp. 1839-1855 ◽  
Author(s):  
Benjamin R. Lintner ◽  
William R. Boos
Keyword(s):  
Energy Source ◽  
Energy Transport ◽  
El Nino ◽  
South Pacific ◽  
Radiative Flux ◽  
South Pacific Convergence Zone ◽  
Convergence Zone ◽  
Atmospheric Energy ◽  
Enso Events ◽  
Atmospheric Energy Transport

AbstractThe South Pacific convergence zone (SPCZ) exhibits well-known spatial displacements in response to anomalous sea surface temperatures (SSTs) associated with the El Niño–Southern Oscillation (ENSO). Although dynamic and thermodynamic changes during ENSO events are consistent with observed SPCZ shifts, explanations for these displacements have been largely qualitative. This study applies a theoretical framework based on generalizing arguments about the relationship between the zonal-mean intertropical convergence zone (ITCZ) and atmospheric energy transport (AET) to 2D, permitting quantification of SPCZ displacements during ENSO. Using either resolved atmospheric energy fluxes or estimates of column-integrated moist energy sources, this framework predicts well the observed SPCZ shifts during ENSO, at least when anomalous ENSO-region SSTs are relatively small. In large-amplitude ENSO events, such as the 1997/98 El Niño, the framework breaks down because of the large change in SPCZ precipitation intensity. The AET framework permits decomposition of the ENSO forcing into various components, such as column radiative heating versus surface turbulent fluxes, and local versus remote contributions. Column energy source anomalies in the equatorial central and eastern Pacific dominate the SPCZ shift. Furthermore, although the radiative flux anomaly is larger than the surface turbulent flux anomaly in the SPCZ region, the radiative flux anomaly, which can be viewed as a feedback on the ENSO forcing, accounts for slightly less than half of SPCZ precipitation anomalies during ENSO. This study also introduces an idealized analytical model used to illustrate AET anomalies during ENSO and to obtain a scaling for the SPCZ response to an anomalous equatorial energy source.

scholarly journals The Representation of the South Pacific Convergence Zone in the Twentieth Century Reanalysis

2019 ◽  
Vol 147 (3) ◽  
pp. 841-851 ◽  
Author(s):  
Thomas Harvey ◽  
James A. Renwick ◽  
Andrew M. Lorrey ◽  
Arona Ngari
Keyword(s):  
Twentieth Century ◽  
Southern Oscillation ◽  
South Pacific ◽  
South Pacific Convergence Zone ◽  
Past Century ◽  
Convergence Zone ◽  
The South ◽  
Southwest Pacific ◽  
Surface Observations ◽  
Twentieth Century Reanalysis

Abstract The South Pacific convergence zone (SPCZ) is the largest rainfall feature in the Southern Hemisphere, and is a critical component of the climate for South Pacific island nations and territories. The small size and isolated nature of these islands leaves them vulnerable to short- and long-term changes in the position of the SPCZ. Its position and strength is strongly modulated by El Niño–Southern Oscillation (ENSO), leading to large interannual variability in rainfall across the southwest Pacific including seasonal droughts and pluvials. Currently much of the analysis about SPCZ activity has been restricted to the satellite observation period starting in 1979. Here, the representation of the SPCZ in the Twentieth Century Reanalysis (20CR), which is a three-dimensional atmospheric reconstruction based only on surface observations, is discussed for the period since 1908. The performance of two versions of the 20CR (version 2 and version 2c) in the satellite era is compared with other reanalyses and climate observation products. The 20CR performs well in the satellite era. Extra surface observations spanning the SPCZ region from the longitude of the Cook Islands has improved the representation of the SPCZ during 1908–57 between 20CRv2 and 20CRv2c. The well-established relationship with ENSO is observed in both the representation of mean SPCZ position and intensity, and this relationship remains consistent through the entire 1908–2011 period. This suggests that the ENSO–SPCZ relationship has remained similar over the course of the past century, and gives further evidence that 20CRv2c performs well back to 1908 over the southwest Pacific region.

scholarly journals The South Pacific Convergence Zone as Depicted in Reanalysis and Satellite Products

2021 ◽  
Author(s):  
◽  
Harvey Thomas Luke
Keyword(s):  
Twentieth Century ◽  
Southern Oscillation ◽  
South Pacific ◽  
South Pacific Convergence Zone ◽  
Past Century ◽  
Enso Cycle ◽  
Convergence Zone ◽  
The South ◽  
Southwest Pacific ◽  
Extended Analysis

<p>The South Pacific Convergence Zone (SPCZ) is the largest rainfall feature in the Southern Hemisphere, and is a critical component of the climate of Southwest Pacific Island nations. The small size and isolated nature of these islands leaves them vulnerable to short and long term changes in the position of the SPCZ. Its location and strength is strongly modulated by the El Niño-Southern Oscillation (ENSO) cycle and the Inter-decadal Pacific Oscillation (IPO), leading to large inter-annual and decadal variability in rainfall across the Southwest Pacific. Much of the analysis on the SPCZ has been restricted to the modern period, more specifically the “satellite era”, starting in 1979. Here, the representation of the SPCZ in the Twentieth Century Reanalysis (20CR) product, which reconstructs the three-dimensional state of the atmosphere based only on surface observations is discussed. The performance of two versions of the 20CR (versions 2 and 2c) in the satellite era is tested via inter-comparison with other reanalysis and observational satellite products, before using 20CR version 2c (20CRv2c) to perform extended analysis back to the early twentieth century. This study demonstrates that 20CR performs well in the satellite era, and is considered suitable for extended analysis. It is established that extra data added in the SPCZ region between 20CR versions 2 and 2c has improved the representation of the SPCZ during 1908-1958. Well-established relationships between ENSO and the IPO with the SPCZ are shown to be present through the entire 1908-2011 period, although it is suggested that the physical link between the IPO and the SPCZ has changed between the first and second half of the twentieth century. Finally, evidence of a southward trend of the SPCZ over the past century is presented, potentially due to an expansion of the tropics as a result of climate change.</p>

A 1300-year reconstruction of the South Pacific Convergence Zone using a Pacific-wide tree-ring network

2020 ◽  
Author(s):  
Philippa Higgins ◽  
Jonathan Palmer ◽  
Christian Turney ◽  
Martin Andersen ◽  
Edward Cook
Keyword(s):  
Tree Ring ◽  
General Circulation ◽  
Southern Oscillation ◽  
South Pacific ◽  
Ice Age ◽  
South Pacific Convergence Zone ◽  
Convergence Zone ◽  
Pacific Island ◽  
The South ◽  
Island Communities

&lt;p&gt;The South Pacific Convergence Zone (SPCZ) is the largest driver of precipitation variability over South Pacific island communities during the austral warm season influencing the severity and duration of drought and the frequency of tropical cyclones. The SPCZ is known to exhibit variability on a range of timescales, from intra-seasonal to multidecadal variations, modulated by the Interdecadal Pacific Oscillation (IPO). Despite its climatic and societal importance, determining the causes of low frequency variability in the SPCZ has been hampered by the short instrumental data record, with most comprehensive analyses since the satellite era. Here we report the first paleoclimate reconstruction of the SPCZ, allowing climate variability in the South Pacific region to be explored back to 700 CE. Our 1300-year reconstruction of the SPCZI (South Pacific Convergence Zone Index; the difference between mean sea level pressure between Apia, Samoa and Suva, Fiji) is based on a trans-Pacific network of precisely dated tree-ring proxies. Capturing SPCZ teleconnections from both sides of the Pacific has produced a robust, unbiased reconstruction with excellent reconstruction skill over the entire period. El Ni&amp;#241;o-Southern Oscillation periodicities (&amp;#8764;3-7 years) are pervasive throughout the SPCZI reconstruction. Multidecadal periodicities wax and wane, apparently coinciding with the timing of the Medieval Climate Anomaly (c. 1000-1200 CE) and Little Ice Age (1300-1700 CE). We discuss some of the drivers of SPCZI variability including global dimming events. Our reconstruction helps improve our understanding of past hydroclimatic behaviour in the southwest Pacific and can be used to validate general circulation model projections for Pacific Island communities in the twenty-first century.&lt;/p&gt;

scholarly journals The South Pacific Convergence Zone as Depicted in Reanalysis and Satellite Products

2021 ◽  
Author(s):  
◽  
Harvey Thomas Luke
Keyword(s):  
Twentieth Century ◽  
Southern Oscillation ◽  
South Pacific ◽  
South Pacific Convergence Zone ◽  
Past Century ◽  
Enso Cycle ◽  
Convergence Zone ◽  
The South ◽  
Southwest Pacific ◽  
Extended Analysis

<p>The South Pacific Convergence Zone (SPCZ) is the largest rainfall feature in the Southern Hemisphere, and is a critical component of the climate of Southwest Pacific Island nations. The small size and isolated nature of these islands leaves them vulnerable to short and long term changes in the position of the SPCZ. Its location and strength is strongly modulated by the El Niño-Southern Oscillation (ENSO) cycle and the Inter-decadal Pacific Oscillation (IPO), leading to large inter-annual and decadal variability in rainfall across the Southwest Pacific. Much of the analysis on the SPCZ has been restricted to the modern period, more specifically the “satellite era”, starting in 1979. Here, the representation of the SPCZ in the Twentieth Century Reanalysis (20CR) product, which reconstructs the three-dimensional state of the atmosphere based only on surface observations is discussed. The performance of two versions of the 20CR (versions 2 and 2c) in the satellite era is tested via inter-comparison with other reanalysis and observational satellite products, before using 20CR version 2c (20CRv2c) to perform extended analysis back to the early twentieth century. This study demonstrates that 20CR performs well in the satellite era, and is considered suitable for extended analysis. It is established that extra data added in the SPCZ region between 20CR versions 2 and 2c has improved the representation of the SPCZ during 1908-1958. Well-established relationships between ENSO and the IPO with the SPCZ are shown to be present through the entire 1908-2011 period, although it is suggested that the physical link between the IPO and the SPCZ has changed between the first and second half of the twentieth century. Finally, evidence of a southward trend of the SPCZ over the past century is presented, potentially due to an expansion of the tropics as a result of climate change.</p>

Pacific Meridional Modes without Equatorial Pacific Influence

2021 ◽  
pp. 1-51
Author(s):  
Yu Zhang ◽  
Shiyun Yu ◽  
Dillon J. Amaya ◽  
Yu Kosaka ◽  
Sarah M. Larson ◽  
...  
Keyword(s):  
North Pacific ◽  
Climate Model ◽  
Decadal Variability ◽  
Model Simulation ◽  
Southern Oscillation ◽  
South Pacific ◽  
Tropical Pacific ◽  
South Pacific Convergence Zone ◽  
Convergence Zone ◽  
Atmospheric Teleconnections

AbstractInvestigating Pacific Meridional Modes (PMM) without the influence of tropical Pacific variability is technically difficult if based on observations or fully coupled model simulations due to their overlapping spatial structures. To confront this issue, the present study investigates both North (NPMM) and South PMM (SPMM) in terms of their associated atmospheric forcing and response processes based on a mechanically decoupled climate model simulation. In this experiment, the climatological wind stress is prescribed over the tropical Pacific, which effectively removes dynamically coupled tropical Pacific variability (e.g., the El Niño-Southern Oscillation). Interannual NPMM in this experiment is forced not only by the North Pacific Oscillation, but also by a North Pacific tripole (NPT) pattern of atmospheric internal variability, which primarily forces decadal NPMM variability. Interannual and decadal variability of the SPMM is partly forced by the South Pacific Oscillation. In turn, both interannual and decadal NPMM variability can excite atmospheric teleconnections over the Northern Hemisphere extratropics by influencing the meridional displacement of the climatological intertropical convergence zone throughout the whole year. Similarly, both interannual and decadal SPMM variability can also excite atmospheric teleconnections over the Southern Hemisphere extratropics by extending/shrinking the climatological South Pacific convergence zone in all seasons. Our results highlight a new poleward pathway by which both the NPMM and SPMM feed back to the extratropical climate, in addition to the equatorward influence on tropical Pacific variability.

Preindustrial to modern variability of sea surface temperatures and CO2 uptake in the South Pacific

2020 ◽  
Author(s):  
Sara Todorovic ◽  
Henry C. Wu ◽  
Braddock K. Linsley ◽  
Henning Kuhnert ◽  
Delphine Dissard
Keyword(s):  
Global Climate ◽  
Climate Change Impacts ◽  
South Pacific ◽  
Sea Surface ◽  
Co2 Uptake ◽  
The South ◽  
Climatic Fluctuations ◽  
Ph Variation ◽  
The Pacific ◽  
Instrumental Records

&lt;p&gt;The modern increase in atmospheric CO&lt;sub&gt;2&lt;/sub&gt; driven by fossil fuel combustion and land-use change is warming our atmosphere and surface oceans. The absorption of this excess CO&lt;sub&gt;2&lt;/sub&gt; by the oceans decreases seawater pH in a process known as ocean acidification (OA), which represents a threat to marine ecosystems with adverse impacts on coral health. It is important to understand how modern climate change impacts interannual and interdecadal climatic cycles and atmospheric phenomena which are originating in the Pacific and modulating global climate. There is a scarcity of data necessary to study the impacts of these changes on natural variability on longer timescales. In this study, we present multi-proxy (e.g. Sr/Ca, &amp;#948;&lt;sup&gt;18&lt;/sup&gt;O, &amp;#948;&lt;sup&gt;13&lt;/sup&gt;C, B/Ca) reconstructions of sea surface temperature (SST), surface seawater carbonate chemistry, with implications for pH variability of the South Pacific back to preindustrial times. This region of the Pacific is interesting for tracking the development of OA because of the well-constrained interannual to interdecadal SST and SSS variability from existing coral-based reconstructions. Massive corals (&lt;em&gt;Porites&lt;/em&gt; sp.) from Rotuma and Tonga will be analyzed to extend the currently available SST reconstructions and expand the spatio-temporal coverage beyond the instrumental records. New monthly-resolved SST records will provide larger analyses exploring the influence of interannual and decadal-interdecadal climatic fluctuations on CO&lt;sub&gt;2&lt;/sub&gt; absorption and pH variation. We aim to quantify the anthropogenic impact on SST, pH and the ocean carbonate system to achieve a better understanding of the status in the South Pacific under open ocean conditions.&lt;/p&gt;

Impacts of Detoured Madden-Julian Oscillations on the South Pacific Convergence Zone

2021 ◽  
pp. 1-41
Author(s):  
Lei Zhou ◽  
Ruomei Ruan ◽  
Raghu Murtugudde
Keyword(s):  
Southern Hemisphere ◽  
Rossby Waves ◽  
South Pacific ◽  
South Pacific Convergence Zone ◽  
Boreal Winter ◽  
Convergence Zone ◽  
The South ◽  
Maritime Continent ◽  
Meridional Winds ◽  
Southern Pacific Ocean

AbstractMadden-Julian Oscillations (MJOs) are a major component of tropical intraseasonal variabilities. There are two paths for MJOs across the Maritime Continent; one is a detoured route into the Southern Hemisphere and the other one is around the equator across the Maritime Continent. Here, it is shown that the detoured and non-detoured MJOs have significantly different impacts on the South Pacific convergence zone (SPCZ). The detoured MJOs trigger strong cross-equatorial meridional winds from the Northern Hemisphere into the Southern Hemisphere. The associated meridional moisture and energy transports due to the background states carried by the intraseasonal meridional winds are favorable for reinforcing the SPCZ. In contrast, the influences of non-detoured MJOs on either hemisphere or the meridional transports across the equator are much weaker. The detoured MJOs can extend their impacts to the surrounding regions by shedding Rossby waves. Due to different background vorticity during detoured MJOs in boreal winter, more ray paths of Rossby waves traverse the Maritime Continent connecting the southern Pacific Ocean and the eastern Indian Ocean, but far fewer Rossby wave paths traverse Australia. Further studies on such processes are expected to contribute to a better understanding of extreme climate and natural disasters on the rim of the southern Pacific and Indian Oceans.

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