scholarly journals A modelling study of the 1976 climate regime shift in the North Pacific Ocean

1999 ◽  
Vol 56 (12) ◽  
pp. 2450-2462 ◽  
Author(s):  
Julia Qiuying Wu ◽  
William W Hsieh
Keyword(s):  
Pacific Ocean ◽  
North Pacific ◽  
General Circulation ◽  
Regime Shift ◽  
North Pacific Ocean ◽  
Circulation Model ◽  
Climate Regime ◽  
Climate Regime Shift ◽  
The North ◽  
The North Pacific

Around 1976, the North Pacific Ocean underwent a climate regime shift, with significant biological consequences. To model the changes in the ocean, an ocean general circulation model was forced by the wind stress and sea surface temperature monthly climatology of the 1952-1975 period in one numerical experiment and the 1976-1988 period in another. Changes in the ocean model between the two experiments revealed how the ocean might have changed under the 1976 climate regime shift. In winter, the intensified post-1976 Aleutian Low spun up the subarctic gyre and the subtropical gyre, except in the Gulf of Alaska, where the circulation weakened. Upwelling was generally enhanced in the subarctic and downwelling enhanced in the subtropical region, with temperature changes down to 600 m. In the post-1976 period, the meridional heat transports were also enhanced: poleward in the low latitudes, equatorward in the midlatitudes, and poleward in the high latitudes.

Decadal changes in growth and recruitment of Pacific halibut (Hippoglossus stenolepis)

1999 ◽  
Vol 56 (2) ◽  
pp. 242-252 ◽  
Author(s):  
William G Clark ◽  
Steven R Hare ◽  
Ana M Parma ◽  
Patrick J Sullivan ◽  
Robert J Trumble
Keyword(s):  
North Pacific ◽  
Regime Shift ◽  
Assessment Model ◽  
Individual Growth ◽  
Climate Regime ◽  
Climate Regime Shift ◽  
The North ◽  
Pacific Halibut ◽  
Hippoglossus Stenolepis ◽  
The North Pacific

Since the climate regime shift of 1976-1977 in the North Pacific, the individual growth of Pacific halibut (Hippoglossus stenolepis) has decreased dramatically in Alaska but not in British Columbia. Recruitment has increased dramatically in both areas. The decrease in age-specific vulnerability to commercial longline gear resulted in a persistent underestimation of incoming recruitment by the age-structured assessment method (CAGEAN) that was used to assess the stock. This problem has been corrected by adding temporal trends in growth and fishery selectivity to the assessment model. The recent sustained high level of recruitment at high levels of spawning biomass has erased the previous appearance of strong density dependence in the stock-recruitment relationship and prompted a reduction in the target full-recruitment harvest rate from 30-35 to 20-25%. The climate regime shift affected a number of other stocks of vertebrates and invertebrates in the North Pacific. While the general oceanographic changes have now been identified, the specific biological mechanisms responsible for the observed changes have not.

scholarly journals Sensitivity of the Simulated Distributions of Water Masses, CFCs, and Bomb 14C to Parameterizations of Mesoscale Tracer Transports in a Model of the North Pacific

2006 ◽  
Vol 36 (3) ◽  
pp. 273-285 ◽  
Author(s):  
Yongfu Xu ◽  
Shigeaki Aoki ◽  
Koh Harada
Keyword(s):  
North Pacific ◽  
General Circulation ◽  
Western North Pacific ◽  
North Pacific Ocean ◽  
Circulation Model ◽  
Water Masses ◽  
Intermediate Water ◽  
North Pacific Intermediate Water ◽  
The North ◽  
The North Pacific

Abstract A basinwide ocean general circulation model of the North Pacific Ocean is used to study the sensitivity of the simulated distributions of water masses, chlorofluorocarbons (CFCs), and bomb carbon-14 isotope (14C) to parameterizations of mesoscale tracer transports. Five simulations are conducted, including a run with the traditional horizontal mixing scheme and four runs with the isopycnal transport parameterization of Gent and McWilliams (GM). The four GM runs use different values of isopycnal and skew diffusivities. Simulated results show that the GM mixing scheme can help to form North Pacific Intermediate Water (NPIW). Greater isopycnal diffusivity enhances formation of NPIW. Although greater skew diffusivity can also generate NPIW, it makes the subsurface too fresh. Results from simulations of CFC uptake show that greater isopycnal diffusivity generates the best results relative to observations in the western North Pacific. The model generally underestimates the inventories of CFCs in the western North Pacific. The results from simulations of bomb 14C reproduce some observed features. Greater isopycnal diffusivity generates a longitudinal gradient of the inventory of bomb 14C from west to east, whereas greater skew diffusivity makes it reversed. It is considered that the ratio of isopycnal diffusivity to skew diffusivity is important. An increase in isopycnal diffusivity increases storage of passive tracers in the subtropical gyre.

scholarly journals Data Sensitivity of the ECCO State Estimate in a Regional Setting

2009 ◽  
Vol 26 (11) ◽  
pp. 2420-2443 ◽  
Author(s):  
Elizabeth Douglass ◽  
Dean Roemmich ◽  
Detlef Stammer
Keyword(s):  
North Pacific ◽  
General Circulation ◽  
Initial Conditions ◽  
North Pacific Ocean ◽  
Circulation Model ◽  
Data Consistency ◽  
Consistent Estimate ◽  
Regional Setting ◽  
The North ◽  
The North Pacific

Abstract The Estimating the Circulation and Climate of the Ocean (ECCO) consortium provides a framework in which the adjoint method of data assimilation is applied to a general circulation model to provide a dynamically self-consistent estimate of the time-varying ocean state, which is constrained by observations. In this study, the sensitivity of the solution to the constraints provided by various datasets is investigated in a regional setting in the North Pacific. Four assimilation experiments are performed, which vary by the data used as constraints and the relative weights associated with these data. The resulting estimates are compared to two of the assimilated datasets as well as to data from two time series stations not used as constraints. These comparisons demonstrate that increasing the weights of the subsurface data provides overall improvement in the model–data consistency of the estimate of the state of the North Pacific Ocean. However, some elements of the solution are degraded. This could result from incompatibility between datasets, possibly because of hidden biases, or from errors in the model physics made more evident by the increased weight on subsurface data. The adjustments to the control parameters of surface forcing and initial conditions necessary to obtain the more accurate fit to the data are found to be within prior error bars.

scholarly journals The 1976/77 North Pacific Climate Regime Shift: The Role of Subtropical Ocean Adjustment and Coupled Ocean–Atmosphere Feedbacks*

2005 ◽  
Vol 18 (23) ◽  
pp. 5125-5140 ◽  
Author(s):  
Lixin Wu ◽  
Dong Eun Lee ◽  
Zhengyu Liu
Keyword(s):  
Ocean Circulation ◽  
North Pacific ◽  
Regime Shift ◽  
Climate Regime ◽  
Climate Regime Shift ◽  
Modeling Approach ◽  
The North ◽  
Ocean Atmosphere ◽  
Decadal Climate ◽  
The North Pacific

Abstract In this study, a new modeling approach is used to look for potential causes of the North Pacific decadal climate regime shift. This new modeling approach is specifically designed to assess not only how changes of the wind-driven ocean circulation induce SST variability, but also the subsequent feedback to climate. Observations appear to indicate that the 1970s North Pacific climate regime shift may be attributed to the coupled ocean–atmosphere interaction over the North Pacific in response to persistent wind stress anomalies in the previous decade. This tends to be supported by modeling results, which suggest that the delayed adjustment of the subtropical ocean circulation may generate sea surface temperature (SST) anomalies in the western subtropical Pacific that may potentially induce a shift of atmospheric circulation, leading to a change of SST in the central and midlatitude North Pacific. This study appears to unify the recent contradictory views of the roles of ocean circulation in the North Pacific decadal climate variability.

scholarly journals Simulation of global distribution of rare earth elements in the ocean using an ocean general circulation model

2021 ◽  
Author(s):  
Akira Oka ◽  
Hirofumi Tazoe ◽  
Hajime Obata
Keyword(s):  
North Pacific ◽  
General Circulation ◽  
North Pacific Ocean ◽  
Circulation Model ◽  
Ocean General Circulation Model ◽  
Vertical Profiles ◽  
Coastal Regions ◽  
The North ◽  
Ocean General Circulation ◽  
The North Pacific

AbstractIn this study, we report our ocean general circulation model simulations of the global distribution of rare earth elements (REEs) in the ocean. As previously reported (Oka et al. in Glob Biogeochem Cycles 23:1–16, 2009), the vertical profiles of REEs in the North Pacific Ocean are strongly controlled by the reversible scavenging process, and the systematic differences between REEs can be reproduced in the model by selecting an appropriate model parameter which controls affinity to particles. We here demonstrate that the external REE input from the coastal regions also plays a role in controlling the vertical profiles of dissolved REE and their inter-basin differences. The role of the external inputs is especially important for light REEs, such as neodymium (Nd). The linear increase in Nd concentration in the North Pacific Ocean cannot be sufficiently reproduced by the reversible scavenging alone; rather, a combination of the reversible scavenging and the external inputs is necessary. On the other hand, the distribution of heavy REEs, such as lutetium (Lu), can be broadly reproduced without the external inputs, suggesting that Lu has similarity with conservative nutrient-like tracer. When compared with REE observations compiled from both the recently obtained GEOTRACES dataset and pre-GEOTRACES reported data, our simulations successfully reproduced the overall features of these observations. Observational data suggested that the vertical profiles of REEs are not the same among the basins; our model simulations demonstrate that this feature can be clearly reproduced by considering both the reversible scavenging and the external REE inputs from the coastal regions.

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