scholarly journals An ocean modeling study to quantify wind forcing and oceanic mixing effects on the tropical North Pacific subsurface warm bias in CMIP and OMIP simulations

2021 ◽  
Author(s):  
Yuchao Zhu ◽  
Rong-Hua Zhang ◽  
Delei Li
Keyword(s):  
North Pacific ◽  
Ocean Modeling ◽  
Wind Forcing ◽  
Warm Bias ◽  
Mixing Effects ◽  
Modeling Study

Wind-Driven Variability of the Subtropical North Pacific Ocean

2012 ◽  
Vol 42 (12) ◽  
pp. 2089-2100 ◽  
Author(s):  
Donata Giglio ◽  
Dean Roemmich ◽  
Sarah T. Gille
Keyword(s):  
Pacific Ocean ◽  
North Pacific ◽  
Time Scale ◽  
North Pacific Ocean ◽  
Region Of Interest ◽  
Major Axis ◽  
Wind Forcing ◽  
Argo Data ◽  
Statistical Confidence ◽  
Decadal Scale

Abstract The Argo array provides a unique dataset to explore variability of the subsurface ocean interior. This study considers the subtropical North Pacific Ocean during the period from 2004 to 2011, when Argo coverage has been relatively complete in time and space. Two distinct patterns of Argo dynamic height transport function () are observed: in 2004/05, the gyre is stronger, and in 2008/09 it is weaker. The orientation of the subtropical gyre also shifts over time: the predominantly zonal major axis shifts to a more northwest–southeast orientation in 2004/05 and to a more southwest–northeast orientation in 2008/09. The limited temporal range of the Argo observations does not allow analysis of the correlation of ocean transport and wind forcing in the basin for the multiyear time scale (6–8-yr period) typical of the dominant gyre patterns. The meridional geostrophic transport anomaly between 180° and 150°E is computed both from Argo data (0–2000 db) and from the Sverdrup relation (using reanalysis winds): similarities are observed in a latitude–time plane, consistent with local forcing playing an important role. A forcing contribution from the eastern subtropics will also reach the region of interest, but on a longer time scale, and it is not analyzed in this study. Compared with the 8-yr Argo record, the longer 19-yr time series of satellite altimetry shows a similar but somewhat modified pattern of variability. A longer Argo record will be needed to observe the decadal-scale fluctuations, to separate interannual and decadal signals, and to ensure statistical confidence in relating the wind forcing and the oceanic response.

scholarly journals An Ocean Modeling Study To Quantify Wind Forcing and Oceanic Mixing Effects on The Tropical North Pacific Subsurface Warm Bias in CMIP and OMIP Simulations

2021 ◽  
Author(s):  
Yuchao Zhu ◽  
Rong-Hua Zhang ◽  
Delei Li
Keyword(s):  
Boundary Layer ◽  
North Pacific ◽  
Thermal Structure ◽  
Vertical Mixing ◽  
Upper Ocean ◽  
Subsurface Temperature ◽  
Mixing Processes ◽  
Warm Bias ◽  
The Past ◽  
Upper Boundary

Abstract Sea surface temperature (SST) bias in the climate models has been a focus in the past, but subsurface temperature biases have not been received much attention yet. In this study, subsurface temperature biases in the Tropical North Pacific (TNP) are investigated by analyzing the CMIP6, CMIP5 and OMIP products, and performing ocean model simulations. It is found that almost all the CMIP and OMIP simulations have a pronounced subsurface warm bias (SWB) in the northeastern tropical Pacific (NETP), and the model developments over the past decade do not indicate obvious improvements in bias pattern and magnitude from CMIP5 to the latest version CMIP6. This SWB is primarily caused by the model deficiencies in the simulated surface wind stress curl (WSC) in the NETP, which is too weak to produce a sufficient Ekman upwelling, a bias that also exists in OMIP simulations. The uncertainties in the parameterizations of the oceanic vertical mixing processes also make a great contribution, and it is demonstrated that the estimated oceanic vertical diffusivities are overestimated both in the upper boundary layer and the interior in the CMIP and OMIP simulations. The relationship between the SWB and the misrepresented oceanic vertical mixing processes are investigated by conducting several ocean-only experiments, in which the upper boundary layer mixing is modified by reducing the wind stirring effect in the Kraus-Turner type bulk mixed-layer approach, and the interior mixing is constrained by using the Argo-derived diffusivity. By applying these modifications to oceanic vertical mixing schemes, the SWB is greatly reduced in the NETP. The consequences of this SWB are further analyzed. Because the thermal structure in the NETP can influence the simulations of oceanic circulations and equatorial upper-ocean thermal structure, the large SWB in the CMIP6 models tends to produce a weak equatorward water transport in the subsurface TNP, a weak equatorial upwelling and a warm equatorial upper ocean.

Wind forcing due to synoptic storm activity over the North Pacific Ocean

1981 ◽  
Vol 19 (2) ◽  
pp. 128-147 ◽  
Author(s):  
Robert L. Haney ◽  
Michael S. Risch ◽  
Gary C. Heise
Keyword(s):  
Pacific Ocean ◽  
North Pacific ◽  
North Pacific Ocean ◽  
Wind Forcing ◽  
Storm Activity ◽  
The North ◽  
The North Pacific

Subsurface warm biases in the tropical Atlantic and their attributions to the role of wind forcing and ocean vertical mixing

2022 ◽  
pp. 1-28
Keyword(s):  
Climate Models ◽  
Heat Budget ◽  
Thermal Structure ◽  
Vertical Mixing ◽  
Wind Forcing ◽  
Climate Simulation ◽  
Tropical Atlantic ◽  
Warm Bias ◽  
Budget Analysis ◽  
Almost All

Abstract Realistic ocean subsurface simulations of thermal structure and variation are critically important to the success in climate prediction and projection; currently, substantial systematic subsurface biases still exist in the state-of-the-art ocean and climate models. In this paper, subsurface biases in the tropical Atlantic (TA) are investigated by analyzing simulations from OMIP and conducting POP2-based ocean-only experiments. The subsurface biases are prominent in almost all OMIP simulations, characterized by two warm bias patches off the equator. By conducting two groups of POP2-based ocean-only experiments, two potential origins of the biases are explored, including uncertainties in wind forcing and vertical mixing parameterization, respectively. It is illustrated that the warm bias near 10° N can be slightly reduced by modulating prescribed wind field, and the warm biases over the entire basin are significantly reduced by reducing background diffusivity in the ocean interior in ways to match observations. By conducting heat budget analysis, it is found that the improved subsurface simulations are attributed to the enhanced cooling effect by constraining the vertical mixing diffusivity in terms of the observational estimate, implying that the overestimation of vertical mixing is primarily responsible for the subsurface warm biases in the TA. Since the climate simulation is very sensitive to the vertical mixing parameterization, more accurate representations of ocean vertical mixing are clearly needed in ocean and climate models.

scholarly journals What controls biological productivity in coastal upwelling systems? Insights from a comparative modeling study

2011 ◽  
Vol 8 (3) ◽  
pp. 5617-5652 ◽  
Author(s):  
Z. Lachkar ◽  
N. Gruber
Keyword(s):  
Coastal Upwelling ◽  
Current System ◽  
Nutrient Recycling ◽  
Comparative Modeling ◽  
Ocean Modeling ◽  
Residence Times ◽  
Biological Productivity ◽  
Regional Ocean Modeling System ◽  
California Current System ◽  
Modeling Study

Abstract. The magnitude of the biological productivity in Eastern Boundary Upwelling Systems (EBUS) is traditionally viewed as directly reflecting the upwelling intensity. Yet, different EBUS show different sensitivities of productivity to upwelling-favorable winds (Carr and Kearns, 2003). Here, using a comparative modeling study of the California Current System (California CS) and Canary Current System (Canary CS), we show how physical and environmental factors, such as light, temperature and cross-shore circulation modulate the response of biological productivity to upwelling strength. To this end, we made a series of eddy-resolving simulations of the California CS and Canary CS using the Regional Ocean Modeling System (ROMS), coupled to a nitrogen based Nutrient-Phytoplankton-Zooplankton-Detritus (NPZD) ecosystem model. We find the nutrient content of the euphotic zone to be 20 % smaller in the Canary CS relative to the California CS. Yet, the biological productivity is 50 % smaller in the latter. This is due to: (1) a faster nutrient-replete growth in the Canary CS relative to the California CS, related to a more favorable light and temperature conditions in the Canary CS, and (2) the longer nearshore water residence times in the Canary CS which lead to larger buildup of biomass in the upwelling zone, thereby enhancing the productivity. The longer residence times in the Canary CS appear to be associated with the wider continental shelves and the lower eddy activity characterizing this upwelling system. This results in a weaker offshore export of nutrients and organic matter, thereby increasing local nutrient recycling and enhancing the coupling between new and export production in the Northwest African system. Our results suggest that climate change induced perturbations such as upwelling favorable wind intensification might lead to contrasting biological responses in the California CS and the Canary CS, with major implications for the biogeochemical cycles and fisheries in these two ecosystems.

Propagation of Rossby Waves over Ridges Excited by Interannual Wind Forcing in a Western North Pacific Model

2004 ◽  
Vol 60 (2) ◽  
pp. 329-340 ◽  
Author(s):  
Kiyoshi Tanaka ◽  
Motoyoshi Ikeda
Keyword(s):  
North Pacific ◽  
Western North Pacific ◽  
Rossby Waves ◽  
Wind Forcing
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