Physical forcing and the dynamics of the pelagic ecosystem in the eastern tropical Pacific: simulations with ENSO-scale and global-warming climate drivers

2003 ◽  
Vol 60 (9) ◽  
pp. 1161-1175 ◽  
Author(s):  
George M Watters ◽  
Robert J Olson ◽  
Robert C Francis ◽  
Paul C Fiedler ◽  
Jeffrey J Polovina ◽  
...  
Keyword(s):  
Global Warming ◽  
Phytoplankton Biomass ◽  
Southern Oscillation ◽  
Tropical Pacific ◽  
Trophic Levels ◽  
Eastern Tropical Pacific ◽  
Ecosystem Models ◽  
Pelagic Ecosystem ◽  
Physical Forcing ◽  
Physical Effects

We used a model of the pelagic ecosystem in the eastern tropical Pacific Ocean to explore how climate variation at El Niño – Southern Oscillation (ENSO) scales might affect animals at middle and upper trophic levels. We developed two physical-forcing scenarios: (1) physical effects on phytoplankton biomass and (2) simultaneous physical effects on phytoplankton biomass and predator recruitment. We simulated the effects of climate-anomaly pulses, climate cycles, and global warming. Pulses caused oscillations to propagate through the ecosystem; cycles affected the shapes of these oscillations; and warming caused trends. We concluded that biomass trajectories of single populations at middle and upper trophic levels cannot be used to detect bottom-up effects, that direct physical effects on predator recruitment can be the dominant source of interannual variability in pelagic ecosystems, that such direct effects may dampen top-down control by fisheries, and that predictions about the effects of climate change may be misleading if fishing mortality is not considered. Predictions from ecosystem models are sensitive to the relative strengths of indirect and direct physical effects on middle and upper trophic levels.

scholarly journals Characterisation of low oxygen extreme events in the Eastern Tropical Pacific between 1979 and 2016

2020 ◽  
Author(s):  
Eike Eduard Köhn ◽  
Matthias Münnich ◽  
Meike Vogt ◽  
Nicolas Gruber
Keyword(s):  
Extreme Events ◽  
Extreme Event ◽  
Southern Oscillation ◽  
Tropical Pacific ◽  
Low Oxygen ◽  
Eastern Tropical Pacific ◽  
Oxygen Minimum Zones ◽  
Mesoscale Dynamics ◽  
Detection And Tracking ◽  
The Pacific

<div>The oxygen minimum zones (OMZs) in the Eastern Tropical Pacific (ETP)</div><div>have expanded over the past 50 years, likely leading to more frequent and more</div><div>intense low oxygen extreme events. This has potentially far-reaching implica-</div><div>tions for e.g., the production of the climate-relevant gas nitrous oxide or the</div><div>reduction of habitat for fish and zooplankton. Yet, to date our understanding</div><div>of the distribution and characteristics of low oxygen extreme events in the ETP</div><div>remains limited.</div><div> </div><div>To fill this gap, we study low oxygen extremes in the ETP using results from</div><div>an eddy-resolution hindcast simulation with the coupled physical-biogeochemical</div><div>model ROMS-BEC for the Pacific from 1979 to 2016. Our setup permits us to</div><div>simulate oxygen variability in the ETP affected by processes on a broad range</div><div>of scales, from climate modes down to mesoscale dynamics. We detect and</div><div>track low oxygen extreme events in the upper 500 meters of the ETP, by ap-</div><div>plying temporally constant statistical thresholds to the hindcast simulation and</div><div>requiring a minimum event duration of 5 days. While most extremes last less</div><div>than 10 days and are of small volumetric extent, about 15% of the extremes</div><div>exist for over a month. The diversity of the long-lasting extremes is dominated</div><div>by westward propagating low oxygen eddies, which are mostly generated in the</div><div>near-coastal area. Superimposed inter-annual variability associated with the El</div><div>Niño-Southern Oscillation (ENSO) leads to a decrease in mesoscale extremes</div><div>during El Niño periods. Along the boundaries of the ETP OMZs transient</div><div>shoaling events of the oxycline linked to ENSO dynamics or the seasonal cycle</div><div>contribute to the generation of further pronounced low oxygen extreme events.</div><div> </div><div>The presented detection and tracking of low oxygen extremes is an important</div><div>step towards a better understanding of extreme event occurrences and charac-</div><div>teristics and lays the groundwork for further research such as the biogeochemical</div><div>impact of such extremes.</div>

scholarly journals Tropical Pacific Climate and Its Response to Global Warming in the Kiel Climate Model

2009 ◽  
Vol 22 (1) ◽  
pp. 71-92 ◽  
Author(s):  
W. Park ◽  
N. Keenlyside ◽  
M. Latif ◽  
A. Ströh ◽  
R. Redler ◽  
...  
Keyword(s):  
Global Warming ◽  
Climate Model ◽  
Southern Oscillation ◽  
Global Climate ◽  
Global Climate Model ◽  
Co2 Concentration ◽  
Tropical Pacific ◽  
Equatorial Pacific ◽  
Cold Bias ◽  
The Tropical Pacific

Abstract A new, non-flux-corrected, global climate model is introduced, the Kiel Climate Model (KCM), which will be used to study internal climate variability from interannual to millennial time scales and climate predictability of the first and second kind. The version described here is a coarse-resolution version that will be employed in extended-range integrations of several millennia. KCM’s performance in the tropical Pacific with respect to mean state, annual cycle, and El Niño–Southern Oscillation (ENSO) is described. Additionally, the tropical Pacific response to global warming is studied. Overall, climate drift in a multicentury control integration is small. However, KCM exhibits an equatorial cold bias at the surface of the order 1°C, while strong warm biases of several degrees are simulated in the eastern tropical Pacific on both sides off the equator, with maxima near the coasts. The annual and semiannual cycles are realistically simulated in the eastern and western equatorial Pacific, respectively. ENSO performance compares favorably to observations with respect to both amplitude and period. An ensemble of eight greenhouse warming simulations was performed, in which the CO2 concentration was increased by 1% yr−1 until doubling was reached, and stabilized thereafter. Warming of equatorial Pacific sea surface temperature (SST) is, to first order, zonally symmetric and leads to a sharpening of the thermocline. ENSO variability increases because of global warming: during the 30-yr period after CO2 doubling, the ensemble mean standard deviation of Niño-3 SST anomalies is increased by 26% relative to the control, and power in the ENSO band is almost doubled. The increased variability is due to both a strengthened (22%) thermocline feedback and an enhanced (52%) atmospheric sensitivity to SST; both are associated with changes in the basic state. Although variability increases in the mean, there is a large spread among ensemble members and hence a finite probability that in the “model world” no change in ENSO would be observed.

scholarly journals Assessment of Responses of Tropical Pacific Air–Sea CO2 Flux to ENSO in 14 CMIP5 Models

2017 ◽  
Vol 30 (21) ◽  
pp. 8595-8613 ◽  
Author(s):  
Fang Dong ◽  
Yangchun Li ◽  
Bin Wang
Keyword(s):  
Interannual Variation ◽  
Dissolved Inorganic Carbon ◽  
Southern Oscillation ◽  
Tropical Pacific ◽  
Total Alkalinity ◽  
Cmip5 Models ◽  
Surface Seawater ◽  
Eastern Tropical Pacific ◽  
Enso Events ◽  
Central Eastern

Responses of tropical Pacific air–sea CO2 flux (fCO2) to El Niño–Southern Oscillation (ENSO) events in 14 models from phase 5 of the Coupled Model Intercomparison Project (CMIP5) are examined. The contributions of sea surface temperature (SST), dissolved inorganic carbon in surface seawater (DIC), and total alkalinity of surface seawater (TALK) to interannual variation of ln(pCO2sea) (instead of partial pressure of CO2 in surface seawater pCO2sea) are quantified based on standardized empirical orthogonal function (EOF) results. Results show that six of the models have poor responses because they fail to reproduce observed interannual variation of pCO2sea in the central-eastern tropical Pacific. These six models underestimate the contribution of DIC interannual variation to interannual variation of pCO2sea in the central-eastern tropical Pacific due to a weak relation between interannual variation of upwelling and ENSO events or a weak relation (including no relation) between interannual variation of upwelling and that of DIC. Furthermore, some models have biases in interannual variation of DIC, in terms of both location and period, that are associated with interannual variation of modeled precipitation. It is also found that two models produce unreasonable interannual variation of bioproductivity, which enlarges interannual variation of DIC in the central-eastern tropical Pacific; this may partly explain why the influence of upwelling on interannual variation of DIC is weak in these models, even when the relationship between interannual variation of DIC and ENSO index is reasonable.

scholarly journals Ocean salinity indices of interannual modes in the tropical Pacific

2021 ◽  
Author(s):  
Jianwei Chi ◽  
Tangdong Qu ◽  
Yan Du ◽  
Jifeng Qi ◽  
Ping Shi
Keyword(s):  
Global Warming ◽  
El Niño ◽  
El Nino ◽  
Tropical Pacific ◽  
Eastern Pacific ◽  
Dipole Mode ◽  
Eastern Tropical Pacific ◽  
Central Pacific El Niño ◽  
Eastern Pacific El Niño ◽  
The Tropical Pacific

AbstractThis study investigates the interannual modes of the tropical Pacific using salinity from observations, ocean reanalysis output and CMIP6 products. Here we propose two indices of sea surface salinity (SSS), a monopole mode and a dipole mode, to identify the El Niño—South Oscillation (ENSO) and its diversity, respectively. The monopole mode is primarily controlled by atmospheric forcing, namely, the enhanced precipitation that induces negative SSS anomalies across nearly the entire tropical Pacific. The dipole mode is mainly forced by oceanic dynamics, with zonal current transporting fresh water from the western fresh pool into the western-central and salty water from the subtropics into the eastern tropical Pacific. Under a global warming condition, an increase in the monopole and dipole mode variance indicates an increase in both the central and eastern Pacific El Niño variability. The increase in central Pacific El Niño variability is largely due to enhanced vertical stratification during global warming in the upper layer, with intensified zonal advection. An eastern Pacific El Niño-like warming pattern contributes to the increase in eastern Pacific El Niño, with enhanced precipitation over the central-eastern tropical Pacific.

scholarly journals Is There an Optimal ENSO Pattern That Enhances Large-Scale Atmospheric Processes Conducive to Tornado Outbreaks in the United States?

2013 ◽  
Vol 26 (5) ◽  
pp. 1626-1642 ◽  
Author(s):  
Sang-Ki Lee ◽  
Robert Atlas ◽  
David Enfield ◽  
Chunzai Wang ◽  
Hailong Liu
Keyword(s):  
United States ◽  
Large Scale ◽  
Southern Oscillation ◽  
The United States ◽  
Tropical Pacific ◽  
Positive Phase ◽  
Eastern Tropical Pacific ◽  
Climate Signal ◽  
Upper Level ◽  
Tornado Outbreaks

Abstract The record-breaking U.S. tornado outbreaks in the spring of 2011 prompt the need to identify long-term climate signals that could potentially provide seasonal predictability for U.S. tornado outbreaks. This study uses both observations and model experiments to show that a positive phase TransNiño may be one such climate signal. Among the top 10 extreme outbreak years during 1950–2010, seven years including the top three are identified with a strongly positive phase TransNiño. The number of intense tornadoes in April–May is nearly doubled during the top 10 positive TransNiño years from that during 10 neutral years. TransNiño represents the evolution of tropical Pacific sea surface temperatures (SSTs) during the onset or decay phase of the El Niño–Southern Oscillation. A positive phase TransNiño is characterized by colder than normal SSTs in the central tropical Pacific and warmer than normal SSTs in the eastern tropical Pacific. Modeling experiments suggest that warmer than normal SSTs in the eastern tropical Pacific work constructively with colder than normal SSTs in the central tropical Pacific to force a strong and persistent teleconnection pattern that increases both the upper-level westerly and lower-level southwesterly over the central and eastern United States. These anomalous winds advect more cold and dry upper-level air from the high latitudes and more warm and moist lower-level air from the Gulf of Mexico converging into the east of the Rockies, and also increase both the lower-tropospheric (0–6 km) and lower-level (0–1 km) vertical wind shear values therein, thus providing large-scale atmospheric conditions conducive to intense tornado outbreaks over the United States.

scholarly journals Meridional Structure of the Seasonally Varying Mixed Layer Temperature Balance in the Eastern Tropical Pacific

2008 ◽  
Vol 21 (13) ◽  
pp. 3240-3260 ◽  
Author(s):  
Michael J. McPhaden ◽  
Meghan F. Cronin ◽  
Dai C. McClurg
Keyword(s):  
Mixed Layer ◽  
Seasonal Cycle ◽  
Southern Oscillation ◽  
Tropical Pacific ◽  
Heat Fluxes ◽  
Enso Cycle ◽  
Convergence Zone ◽  
Eastern Tropical Pacific ◽  
Mixed Layer Temperature ◽  
Upwelled Water

Abstract The eastern tropical Pacific Ocean is important climatically because of its influence on the El Niño–Southern Oscillation (ENSO) cycle and the American monsoon. Accurate prediction of these phenomena requires a better understanding of the background climatological conditions on which seasonal-to-interannual time-scale anomalies develop in the region. This study addresses the processes responsible for the seasonal cycle of sea surface temperature (SST) in the eastern tropical Pacific using 3 yr (April 2000–March 2003) of moored buoy and satellite data between 8°S and 12°N along 95°W. Results indicate that at all latitudes, surface heat fluxes are important in the mixed layer temperature balance. At 8°S, in a region of relatively deep mean thermocline and mixed layer, local storage of heat crossing the air–sea interface accounts for much of the seasonal cycle in SST. In the equatorial cold tongue and the intertropical convergence zone, where mean upwelling leads to relatively thin mixed layers, vertical turbulent mixing with the upper thermocline is a major contributor to SST change. Lateral temperature advection by seasonally varying large-scale currents is most significant near the equator but is generally of secondary importance. There is a hemispheric asymmetry in seasonal SST variations, with larger amplitudes in the Southern Hemisphere than in the Northern Hemisphere. This asymmetry is mainly due to forcing from the southerly component of the trade winds, which shifts the axis of equatorial upwelling south of the equator while creating an oceanic convergence zone to the north that limits the northward spread of cold upwelled water. In general, results support the Mitchell and Wallace hypothesis about the importance of southerly winds and ocean–atmosphere feedbacks in establishing seasonally varying climatological conditions in the eastern tropical Pacific.

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