scholarly journals The response of the Peruvian Upwelling Ecosystem to centennial-scale global change during the last two millennia

2014 ◽  
Vol 10 (2) ◽  
pp. 715-731 ◽  
Author(s):  
R. Salvatteci ◽  
D. Gutiérrez ◽  
D. Field ◽  
A. Sifeddine ◽  
L. Ortlieb ◽  
...  
Keyword(s):  
Walker Circulation ◽  
Tropical Pacific ◽  
Warm Period ◽  
Ice Age ◽  
Global Changes ◽  
Marine Productivity ◽  
Peruvian Upwelling Ecosystem ◽  
Mean State ◽  
The Walker Circulation ◽  
The Tropical Pacific

Abstract. The tropical Pacific ocean–atmosphere system influences global climate on interannual, decadal, as well as longer timescales. Given the uncertainties in the response of the tropical Pacific to increasing greenhouse gasses, it is important to assess the role of the tropical Pacific climate variability in response to past global changes. The Peruvian Upwelling Ecosystem (PUE) represents an ideal area to reconstruct past changes in the eastern tropical Pacific region because productivity and subsurface oxygenation are strongly linked to changes in the strength of the Walker circulation. Throughout the last 2000 years, warmer (the Roman Warm Period – RWP; the Medieval Climate Anomaly – MCA; and the Current Warm Period – CWP), and colder (the Dark Ages Cold Period – DACP – and Little Ice Age – LIA) intervals were identified in the Northern Hemisphere (NH). We use a multi-proxy approach including organic and inorganic proxies in finely laminated sediments retrieved off Pisco (~14° S), Peru to reconstruct the PUE response to these climatic periods. Our results indicate that the centennial-scale changes in precipitation are associated with changes in the Intertropical Convergence Zone (ITCZ) meridional displacements and expansion/contraction of the South Pacific Sub-tropical High (SPSH). Additionally, during the NH cold periods, the PUE exhibited an El Niño-like mean state, characterized by a weak oxygen minimum zone (OMZ), and low marine productivity. In contrast, during the RWP, the last stage of the MCA and the CWP, the PUE exhibited a La Niña-like mean state, characterized by an intense OMZ and high marine productivity. Comparing our results with other relevant paleoclimatic reconstructions revealed that changes in the Walker circulation strength and the SPSH expansion/contraction controlled marine productivity and OMZ intensity changes during the past two millennia.

scholarly journals The response of the Peruvian Upwelling Ecosystem to centennial-scale global change during the last two millennia

2013 ◽  
Vol 9 (5) ◽  
pp. 5479-5519 ◽  
Author(s):  
R. Salvatteci ◽  
D. Gutiérrez ◽  
D. Field ◽  
A. Sifeddine ◽  
L. Ortlieb ◽  
...  
Keyword(s):  
Walker Circulation ◽  
Tropical Pacific ◽  
Ocean Atmosphere ◽  
Marine Productivity ◽  
Underlying Mechanisms ◽  
The Last Two Millennia ◽  
Peruvian Upwelling Ecosystem ◽  
Mean State ◽  
The Walker Circulation ◽  
The Tropical Pacific

Abstract. The Tropical Pacific ocean-atmosphere system influences global climate on interannual, decadal, as well as at longer timescales. Given the uncertainties in the response of the Tropical Pacific to the ongoing greenhouse effect, it is important to assess the natural range of the Tropical Pacific climate variability in response to global natural changes, and to understand the underlying mechanisms. The Peruvian Upwelling Ecosystem (PUE) represents an ideal area to reconstruct past changes in ocean-atmosphere systems because productivity and subsurface oxygenation are strongly linked to changes in the strength of the Walker circulation. Throughout the last 2000 yr, warmer (the Roman Warm Period [RWP], the Medieval Climate Anomaly [MCA] and the Current Warm Period [CWP]), and colder (the Dark Ages Cold Period [DACP] and Little Ice Age [LIA]) intervals occurred with considerable changes around the globe. In order to reconstruct the PUE response to these climatic periods and reveal the underlying mechanisms, we use a multi-proxy approach including organic and inorganic proxies in finely laminated sediments retrieved off Pisco (~ 14° S), Peru. Our results indicate that the PUE exhibited a La Niña-like mean state during the warm periods, characterized by an intense OMZ and high marine productivity. During cold periods the PUE exhibited an El Niño-like mean state, characterized by a weak OMZ and low marine productivity. Comparing our results with other relevant paleoclimatic reconstructions revealed that changes in the strength of the Walker circulation and the expansion/contraction of the South Pacific Sub-tropical High controlled productivity and subsurface oxygenation in the PUE during the last two millennia. This indicate that large scale circulation changes are the driving forces in maintaining productivity and subsurface oxygenation off Peru at centennial time scales during the past two millennia.

scholarly journals Impact of Resolution on the Tropical Pacific Circulation in a Matrix of Coupled Models

2009 ◽  
Vol 22 (10) ◽  
pp. 2541-2556 ◽  
Author(s):  
Malcolm J. Roberts ◽  
A. Clayton ◽  
M.-E. Demory ◽  
J. Donners ◽  
P. L. Vidale ◽  
...  
Keyword(s):  
Coupled Model ◽  
Walker Circulation ◽  
Ocean Model ◽  
Tropical Pacific ◽  
Coupled Models ◽  
Model Stability ◽  
The Mean ◽  
The Impact ◽  
Mean State ◽  
The Tropical Pacific

Abstract Results are presented from a matrix of coupled model integrations, using atmosphere resolutions of 135 and 90 km, and ocean resolutions of 1° and 1/3°, to study the impact of resolution on simulated climate. The mean state of the tropical Pacific is found to be improved in the models with a higher ocean resolution. Such an improved mean state arises from the development of tropical instability waves, which are poorly resolved at low resolution; these waves reduce the equatorial cold tongue bias. The improved ocean state also allows for a better simulation of the atmospheric Walker circulation. Several sensitivity studies have been performed to further understand the processes involved in the different component models. Significantly decreasing the horizontal momentum dissipation in the coupled model with the lower-resolution ocean has benefits for the mean tropical Pacific climate, but decreases model stability. Increasing the momentum dissipation in the coupled model with the higher-resolution ocean degrades the simulation toward that of the lower-resolution ocean. These results suggest that enhanced ocean model resolution can have important benefits for the climatology of both the atmosphere and ocean components of the coupled model, and that some of these benefits may be achievable at lower ocean resolution, if the model formulation allows.

Recent multidecadal strengthening of the Walker circulation across the tropical Pacific

2013 ◽  
Vol 3 (6) ◽  
pp. 571-576 ◽  
Author(s):  
Michelle L. L’Heureux ◽  
Sukyoung Lee ◽  
Bradfield Lyon
Keyword(s):  
Walker Circulation ◽  
Tropical Pacific ◽  
The Walker Circulation ◽  
The Tropical Pacific

Reconstructing an Interdecadal Pacific Oscillation Index from a Pacific Basin–Wide Collection of Ice Core Records

2021 ◽  
Vol 34 (10) ◽  
pp. 3839-3852
Author(s):  
Stacy E. Porter ◽  
Ellen Mosley-Thompson ◽  
Lonnie G. Thompson ◽  
Aaron B. Wilson
Keyword(s):  
Ice Core ◽  
Ice Cores ◽  
Tropical Pacific ◽  
Ice Age ◽  
Pacific Basin ◽  
Interdecadal Pacific Oscillation ◽  
The Pacific ◽  
Instrumental Period ◽  
The Tropical Pacific ◽  
Ice Core Records

AbstractUsing an assemblage of four ice cores collected around the Pacific basin, one of the first basinwide histories of Pacific climate variability has been created. This ice core–derived index of the interdecadal Pacific oscillation (IPO) incorporates ice core records from South America, the Himalayas, the Antarctic Peninsula, and northwestern North America. The reconstructed IPO is annually resolved and dates to 1450 CE. The IPO index compares well with observations during the instrumental period and with paleo-proxy assimilated datasets throughout the entire record, which indicates a robust and temporally stationary IPO signal for the last ~550 years. Paleoclimate reconstructions from the tropical Pacific region vary greatly during the Little Ice Age (LIA), although the reconstructed IPO index in this study suggests that the LIA was primarily defined by a weak, negative IPO phase and hence more La Niña–like conditions. Although the mean state of the tropical Pacific Ocean during the LIA remains uncertain, the reconstructed IPO reveals some interesting dynamical relationships with the intertropical convergence zone (ITCZ). In the current warm period, a positive (negative) IPO coincides with an expansion (contraction) of the seasonal latitudinal range of the ITCZ. This relationship is not stationary, however, and is virtually absent throughout the LIA, suggesting that external forcing, such as that from volcanoes and/or reduced solar irradiance, could be driving either the ITCZ shifts or the climate dominating the ice core sites used in the IPO reconstruction.

Reduced El Niño variability in the PlioMIP2 model ensemble

2021 ◽  
Author(s):  
Arthur Oldeman ◽  
Michiel Baatsen ◽  
Anna von der Heydt ◽  
Henk Dijkstra ◽  
Julia Tindall
Keyword(s):  
Pacific Ocean ◽  
Spatial Structure ◽  
Spectral Power ◽  
Tropical Pacific ◽  
Tropical Pacific Ocean ◽  
Model Ensemble ◽  
Ensemble Mean ◽  
Mean State ◽  
Sst Gradient ◽  
The Tropical Pacific

<p>The mid-Piacenzian or mid-Pliocene warm period (mPWP, 3.264 – 3.025 Ma) is the most recent geological period to see atmospheric CO­<sub>2</sub> levels similar to the present-day values (~400 ppm). Some proxy reconstructions for the mPWP show reduced zonal SST gradients in the tropical Pacific Ocean, possibly indicating an El Niño-like mean state in the mid-Pliocene. However, past modelling studies do not show the same results. Efforts to understand mPWP climate dynamics have led to the Pliocene Model Intercomparison Project (PlioMIP). Results from the first phase (PlioMIP1) showed clear El Niño variability (albeit significantly reduced) and did not show the greatly reduced time-mean zonal SST gradient suggested by some of the proxies.</p><p>In this work, we study ENSO variability in the PlioMIP2 ensemble, which consists of additional global coupled climate models and updated boundary conditions compared to PlioMIP1. We quantify ENSO amplitude, period and spatial structure as well as the tropical Pacific annual mean state in a mid-Pliocene and pre-industrial reference simulation. Results show a reduced El Niño amplitude in the model- ensemble mean, with 11 out of 13 individual models showing such a reduction. Furthermore, the spectral power of this variability considerably decreases in the 3–7-year band and shifts to higher frequencies compared to pre-industrial. The spatial structure of the dominant EOF shows no particular change in the patterns of tropical Pacific variability in the model-ensemble mean, compared to the pre-industrial. Further analyses that will be presented include the correlation of the zonal SST gradient with the El Niño amplitude, investigation of shift in El Niño flavour, and a discussion of the coupled feedbacks at play in the mid-Pliocene tropical Pacific Ocean.</p>

scholarly journals Hydrological variations in central China over the past millennium and their links to the tropical Pacific and North Atlantic oceans

2020 ◽  
Vol 16 (2) ◽  
pp. 475-485
Author(s):  
Fucai Duan ◽  
Zhenqiu Zhang ◽  
Yi Wang ◽  
Jianshun Chen ◽  
Zebo Liao ◽  
...  
Keyword(s):  
North Atlantic ◽  
Atmospheric Precipitation ◽  
Tropical Pacific ◽  
Meridional Overturning Circulation ◽  
Central China ◽  
Ice Age ◽  
The North ◽  
Future Global Warming ◽  
The North Atlantic ◽  
The Tropical Pacific

Abstract. Variations of precipitation, also called the Meiyu rain, in the East Asian summer monsoon (EASM) domain during the last millennium could help enlighten the hydrological response to future global warming. Here we present a precisely dated and highly resolved stalagmite δ18O record from the Yongxing Cave, central China. Our new record, combined with a previously published one from the same cave, indicates that the Meiyu rain has changed dramatically in association with the global temperature change. In particular, our record shows that the Meiyu rain was weakened during the Medieval Climate Anomaly (MCA) but intensified during the Little Ice Age (LIA). During the Current Warm Period (CWP), our record indicates a similar weakening of the Meiyu rain. Furthermore, during the MCA and CWP, our records show that the atmospheric precipitation is similarly wet in northern China and similarly dry in central China, but relatively wet during the CWP in southern China. This spatial discrepancy indicates a complicated localized response of the regional precipitation to the anthropogenic forcing. The weakened (intensified) Meiyu rain during the MCA (LIA) matches well with the warm (cold) phases of Northern Hemisphere surface air temperature. This Meiyu rain pattern also corresponds well to the climatic conditions over the tropical Indo-Pacific warm pool. On the other hand, our record shows a strong association with the North Atlantic climate as well. The reduced (increased) Meiyu rain correlates well with positive (negative) phases of the North Atlantic Oscillation. In addition, our record links well to the strong (weak) Atlantic meridional overturning circulation during the MCA (LIA) period. All abovementioned localized correspondences and remote teleconnections on decadal to centennial timescales indicate that the Meiyu rain was coupled closely with oceanic processes in the tropical Pacific and North Atlantic oceans during the MCA and LIA.

Evaluating the performance of CMIP6 models in the tropical Atlantic: mean state, variability, and remote impacts

2020 ◽  
Author(s):  
Ingo Richter ◽  
Hiroki Tokinaga
Keyword(s):  
General Circulation ◽  
General Circulation Models ◽  
Tropical Pacific ◽  
Boreal Summer ◽  
Tropical Atlantic ◽  
Westerly Wind ◽  
Equatorial Atlantic ◽  
Wide Range ◽  
Mean State ◽  
The Tropical Pacific

<p>General circulation models of the Coupled Model Intercomparison Project Phase 6 (CMIP6) are examined with respect to their ability to simulate the mean state and variability of the tropical Atlantic, as well as its linkage to the tropical Pacific. While, on average, mean state biases have improved little relative to the previous intercomparison (CMIP5), there are now a few models with very small biases. In particular the equatorial Atlantic warm SST and westerly wind biases are mostly eliminated in these models. Furthermore, interannual variability in the equatorial and subtropical Atlantic is quite realistic in a number of CMIP6 models, which suggests that they should be useful tools for understanding and predicting variability patterns. The evolution of equatorial Atlantic biases follows the same pattern as in previous model generations, with westerly wind biases during boreal spring preceding warm sea-surface temperature (SST) biases in the east during boreal summer. A substantial portion of the westerly wind bias exists already in atmosphere-only simulations forced with observed SST, suggesting an atmospheric origin. While variability is relatively realistic in many models, SSTs seem less responsive to wind forcing than observed, both on the equator and in the subtropics, possibly due to an excessively deep mixed layer originating in the oceanic component. Thus models with realistic SST amplitude tend to have excessive wind amplitude. The models with the smallest mean state biases all have relatively high resolution but there are also a few low-resolution models that perform similarly well, indicating that resolution is not the only way toward reducing tropical Atlantic biases. The results also show a relatively weak link between mean state biases and the quality of the simulated variability. The linkage to the tropical Pacific shows a wide range of behaviors across models, indicating the need for further model improvement.</p>

scholarly journals Biophysical Feedbacks in the Tropical Pacific

2005 ◽  
Vol 18 (1) ◽  
pp. 58-70 ◽  
Author(s):  
Ben Marzeion ◽  
Axel Timmermann ◽  
Ragu Murtugudde ◽  
Fei-Fei Jin
Keyword(s):  
Mixed Layer ◽  
Annual Cycle ◽  
Southern Oscillation ◽  
Heat Budget ◽  
Tropical Pacific ◽  
Shortwave Radiation ◽  
Bjerknes Feedback ◽  
Mean State ◽  
Chlorophyll Concentrations ◽  
The Tropical Pacific

Abstract This study explores the influence of phytoplankton on the tropical Pacific heat budget. A hybrid coupled model for the tropical Pacific that is based on a primitive equation reduced-gravity multilayer ocean model, a dynamic ocean mixed layer, an atmospheric mixed layer, and a statistical atmosphere is used. The statistical atmosphere relates deviations of the sea surface temperature from its mean to wind stress anomalies and allows for the rectification of the annual cycle and the El Niño–Southern Oscillation (ENSO) phenomenon through the positive Bjerknes feedback. Furthermore, a nine-component ecosystem model is coupled to the physical variables of the ocean. The simulated chlorophyll concentrations can feed back onto the ocean heat budget by their optical properties, which modify solar light absorption in the surface layers. It is shown that both the surface layer concentration as well as the vertical profile of chlorophyll have a significant effect on the simulated mean state, the tropical annual cycle, and ENSO. This study supports a previously suggested hypothesis (Timmermann and Jin) that predicts an influence of phytoplankton concentration of the tropical Pacific climate mean state and its variability. The bioclimate feedback diagnosed here works as follows: Maxima in the subsurface chlorophyll concentrations lead to an enhanced subsurface warming due to the absorption of photosynthetically available shortwave radiation. This warming triggers a deepening of the mixed layer in the eastern equatorial Pacific and eventually a reduction of the surface ocean currents (Murtugudde et al.). The weakened south-equatorial current generates an eastern Pacific surface warming, which is strongly enhanced by the Bjerknes feedback. Because of the deepening of the mixed layer, the strength of the simulated annual cycle is also diminished. This in turn leads to an increase in ENSO variability.

Sign in / Sign up

Export Citation Format

Share Document