Potential Impact of the Eurasian Boreal Forest on North Pacific Climate Variability*

2007 ◽  
Vol 20 (6) ◽  
pp. 981-992 ◽  
Author(s):  
Michael Notaro ◽  
Zhengyu Liu
Keyword(s):  
Boreal Forest ◽  
North Pacific ◽  
Vegetation Cover ◽  
Large Scale ◽  
Forest Cover ◽  
Kuroshio Extension ◽  
Vegetation Feedback ◽  
North Asia ◽  
The Impact ◽  
The Kuroshio

Abstract The authors demonstrate that variability in vegetation cover can potentially influence oceanic variability through the atmospheric bridge. Experiments aimed at isolating the impact of variability in forest cover along the poleward side of the Asian boreal forest on North Pacific SSTs are performed using the fully coupled model, Fast Ocean Atmosphere Model–Lund Potsdam Jena (FOAM-LPJ), with dynamic atmosphere, ocean, and vegetation. The northern edge of the simulated Asian boreal forest is characterized by substantial variability in annual forest cover, with an east–west dipole pattern marking its first EOF mode. Simulations in which vegetation cover is allowed to vary over north/central Russia exhibit statistically significant greater SST variance over the Kuroshio Extension. Anomalously high forest cover over North Asia supports a lower surface albedo with higher temperatures and lower sea level pressure, leading to a reduction in cold advection into northern China and in turn a decrease in cold air transport into the Kuroshio Extension region. Variability in the large-scale circulation pattern is indirectly impacted by the aforementioned vegetation feedback, including the enhancement in upper-level jet wind variability along the north–south flanks of the East Asian jet stream.

scholarly journals Influence of the Meridional Shifts of the Kuroshio and the Oyashio Extensions on the Atmospheric Circulation

2011 ◽  
Vol 24 (3) ◽  
pp. 762-777 ◽  
Author(s):  
Claude Frankignoul ◽  
Nathalie Sennéchael ◽  
Young-Oh Kwon ◽  
Michael A. Alexander
Keyword(s):  
Atmospheric Circulation ◽  
North Pacific ◽  
Large Scale ◽  
Kuroshio Extension ◽  
Statistical Significance ◽  
The North ◽  
Enso Teleconnections ◽  
Historical Temperature ◽  
The Kuroshio ◽  
Sst Anomalies

Abstract The meridional shifts of the Oyashio Extension (OE) and of the Kuroshio Extension (KE), as derived from high-resolution monthly sea surface temperature (SST) anomalies in 1982–2008 and historical temperature profiles in 1979–2007, respectively, are shown based on lagged regression analysis to significantly influence the large-scale atmospheric circulation. The signals are independent from the ENSO teleconnections, which were removed by seasonally varying, asymmetric regression onto the first three principal components of the tropical Pacific SST anomalies. The response to the meridional shifts of the OE front is equivalent barotropic and broadly resembles the North Pacific Oscillation/western Pacific pattern in a positive phase for a northward frontal displacement. The response may reach 35 m at 250 hPa for a typical OE shift, a strong sensitivity since the associated SST anomaly is 0.5 K. However, the amplitude, but not the pattern or statistical significance, strongly depends on the lag and an assumed 2-month atmospheric response time. The response is stronger during fall and winter and when the front is displaced southward. The response to the northward KE shifts primarily consists of a high centered in the northwestern North Pacific and hemispheric teleconnections. The response is also equivalent barotropic, except near Kamchatka, where it tilts slightly westward with height. The typical amplitude is half as large as that associated with OE shifts.

scholarly journals Kuroshio Extension Variability and Forcing of the Pacific Decadal Oscillations: Responses and Potential Feedback

2003 ◽  
Vol 33 (12) ◽  
pp. 2465-2482 ◽  
Author(s):  
Bo Qiu
Keyword(s):  
Pacific Ocean ◽  
North Pacific ◽  
Large Scale ◽  
North Pacific Ocean ◽  
Kuroshio Extension ◽  
Atmospheric Forcing ◽  
Mean Flow ◽  
Wind Stress Curl ◽  
The Pacific ◽  
The Kuroshio

Abstract A forcing mechanism is sought for the large-scale circulation changes in the Kuroshio Extension region of the western North Pacific Ocean as inferred by TOPEX/Poseidon sea surface height (SSH) data. The low-frequency signal of the Kuroshio Extension over the last decade was characterized by a modulation in its zonal mean flow intensity: the mean Kuroshio Extension jet weakened progressively from 1993 to 1996 and this trend reversed after 1997. The ability to simulate the major trends in the observed SSH signals with linear vorticity dynamics leads the authors to conclude that the modulation in the zonal mean jet was remotely forced by wind stress curl anomalies in the eastern North Pacific Ocean related to the Pacific decadal oscillations (PDOs). To be specific, the weakening (strengthening) trend in 1993–96 (1997–2001) was caused by westward expansions of negative (positive) SSH anomalies south of the Kuroshio Extension and positive (negative) SSH anomalies north of the Kuroshio Extension. Emergence of oppositely signed SSH anomalies on the two sides of the Kuroshio Extension jet is due to the different propagating speeds of the baroclinic Rossby waves, which carry the wind-induced SSH anomalies generated in the eastern North Pacific at different phases of the PDOs. Hindcasting the Kuroshio Extension jet strength over the last 45 years reveals that the jet modulation has a dominant timescale of ∼12 yr. Given the location of the Kuroshio Extension jet relative to the maximum atmospheric forcing, it is found that this dominant timescale is consistent with the preferred timescale under a stochastic white-noise atmospheric forcing. It is hypothesized that this connection between the Kuroshio Extension strength and the latitudinally dependent baroclinic adjustment contributes to an increase in variance and persistence of the North Pacific midlatitude coupled system on the decadal timescale.

scholarly journals Decadal variability of the Kuroshio Extension: the response of the jet to increased atmospheric resolution in a coupled ocean–atmosphere model

2020 ◽  
Author(s):  
Giusy Fedele ◽  
Alessio Bellucci ◽  
Simona Masina ◽  
Stefano Pierini
Keyword(s):  
Large Scale ◽  
Decadal Variability ◽  
North Pacific Ocean ◽  
Kuroshio Extension ◽  
Low Frequency ◽  
Small Scale ◽  
The North ◽  
Ocean Atmosphere ◽  
The Impact ◽  
The Kuroshio

AbstractThe Kuroshio Extension (KE) shifts between elongated and convoluted states on interannual to decadal time scales. The nature of this low frequency variability (LFV) is still under debate since it is known to be driven by intrinsic oceanic mechanisms, but it is also synchronized with the Pacific Decadal Oscillation (PDO). In this analysis we present the results from two present-climate coupled simulations performed with the CMCC-CM2 model under the CMIP6 HighResMIP protocol and differing only by their atmospheric component resolution. The impact of increased atmospheric resolution on the KE LFV is assessed inspecting several aspects: the KE bimodality, the large-scale variability and the air–sea interactions. The KE LFV and the teleconnection mechanism that connects the KE and the PDO are well captured by both configurations. However, higher atmospheric resolution favors the occurrence of the elongated state and leads to a more realistic PDO representation. Moreover, both simulations qualitatively capture the signatures of atmosphere-driven and ocean-driven regimes over the North Pacific Ocean, even if the higher resolution induces an excessively strong ocean–atmosphere coupling that leads to an overestimation of the air–sea feedbacks. This work highlights that the small scale atmospheric variability (resolution lower than 1°) does not substantially contribute to improve the realism of the KE LFV, but causes significant differences in the air–sea interaction over the KE region likely related to the strengthening of the coupling. The eddy-permitting ocean resolution shared by both configurations is likely responsible for the degree of realism exhibited by the simulated KE LFV in the two analyzed simulations.

The Impact of Kuroshio Extension Fronts Variation on the Pacific Storm Tracks and the relationship with Temperature over North America

2020 ◽  
Author(s):  
Ziniu Xiao
Keyword(s):  
North America ◽  
Temperature Gradient ◽  
Large Scale ◽  
Kuroshio Extension ◽  
Storm Tracks ◽  
Near Surface ◽  
Intensity Index ◽  
Significant Difference ◽  
The Impact ◽  
The Kuroshio

<p>The intensity index of Kuroshio Extension and northern front zones (KEF) is defined as the area average of SST meridional gradient by using Hadley Center’s surface sea temperature dataset (1949-2014), and the Kuroshio Extension frontal intensity index (KEFI) has seasonal to interdecadal variations. In winter, the KEFI has significant positive correlation with transient variances in the North Pacific storm tracks area, and the positive relationship appears when KEFI lead storm tracks one month which indicates the intensity of KEF could influence storm tracks in winter. To investigate the possible mechanism, we found: when the winter SST front is stronger, the more significant difference between ocean-air heat flux in both sides of KEF could strengthen the near-surface temperature gradient, which maintains the near-surface baroclincity and benefits the transient heat transport, promote the develop of transient eddies at last. Additional, the large-scale circulation also be response to KEF in winter: when the KEF is stronger, the Aleutian is deepen, the subtropical high is strengthen, the 500 hPa potential high is increased (decreased) in south (north), the subtropical jet is weaker and wider. It is found that the oceanic fronts promote storm tracks by transporting heat upward and maintaining the air temperature gradient in winter. In further, the significant correlation was found between the Kuroshio Extension Oceanic Front intensity and the temperature over North America in autumn and winter.</p>

scholarly journals Synthesizing published knowledge of boreal forest cover change for large-scale landscape dynamics modelling

2003 ◽  
Vol 79 (1) ◽  
pp. 132-146 ◽  
Author(s):  
Dennis Yemshanov ◽  
Ajith H Perera
Keyword(s):  
Boreal Forest ◽  
Large Scale ◽  
Forest Canopy ◽  
Forest Cover ◽  
Forest Succession ◽  
Simulation Models ◽  
Limiting Factors ◽  
Sources Of Information ◽  
Forest Cover Change ◽  
Discrete State

We reviewed the published knowledge on forest succession in the North American boreal biome for its applicability in modelling forest cover change over large extents. At broader scales, forest succession can be viewed as forest cover change over time. Quantitative case studies of forest succession in peer-reviewed literature are reliable sources of information about changes in forest canopy composition. We reviewed the following aspects of forest succession in literature: disturbances; pathways of post-disturbance forest cover change; timing of successional steps; probabilities of post-disturbance forest cover change, and effects of geographic location and ecological site conditions on forest cover change. The results from studies in the literature, which were mostly based on sample plot observations, appeared to be sufficient to describe boreal forest cover change as a generalized discrete-state transition process, with the discrete states denoted by tree species dominance. In this paper, we outline an approach for incorporating published knowledge on forest succession into stochastic simulation models of boreal forest cover change in a standardized manner. We found that the lack of details in the literature on long-term forest succession, particularly on the influence of pre-disturbance forest cover composition, may be limiting factors in parameterizing simulation models. We suggest that the simulation models based on published information can provide a good foundation as null models, which can be further calibrated as detailed quantitative information on forest cover change becomes available. Key words: probabilistic model, transition matrix, boreal biome, landscape ecology

Effects of commercial thinning on site occupancy and habitat use by spruce grouse in boreal Quebec

2011 ◽  
Vol 41 (3) ◽  
pp. 501-508 ◽  
Author(s):  
Ambroise Lycke ◽  
Louis Imbeau ◽  
Pierre Drapeau
Keyword(s):  
Habitat Use ◽  
Boreal Forest ◽  
Breeding Season ◽  
Vegetation Cover ◽  
Forest Cover ◽  
Site Occupancy ◽  
Lower Proportion ◽  
Large Mammals ◽  
Dense Vegetation ◽  
Commercial Thinning

Partial cuts are increasingly proposed to maintain habitats for species negatively affected by clearcutting, even if their benefits on nonpasserine birds and large mammals are still poorly documented. Our main objective was to evaluate effects of commercial thinning (CT) on spruce grouse ( Falcipennis canadensis L.), a game bird of the boreal forest. Because this species is known to be associated with a dense vegetation cover, we hypothesized that habitat use would be lower in treated sites. In spring 2006, we evaluated site occupancy in 94 forest stands (50 CT and 44 uncut stands) in Quebec by visiting each on three occasions during the breeding season (March–May). Additionally, during the molting period (May–July), we used radiotelemetry to monitor habitat use by 19 males. As compared with uncut stands, results show that a lower proportion of CTs were used in spring (39% versus 60%, after accounting for detection). During the molting period, CTs were also used less than expected according to their availability. The significant reduction of lateral and vertical forest cover in CT may explain these results. We conclude that even if CT is perceived beneficial for wildlife, it does not completely fulfill the needs of species associated with dense understory vegetation, such as spruce grouse.

scholarly journals On the Relationship between Synoptic Wintertime Atmospheric Variability and Path Shifts in the Gulf Stream and the Kuroshio Extension

2009 ◽  
Vol 22 (12) ◽  
pp. 3177-3192 ◽  
Author(s):  
Terrence M. Joyce ◽  
Young-Oh Kwon ◽  
Lisan Yu
Keyword(s):  
North Atlantic ◽  
North Pacific ◽  
Gulf Stream ◽  
Kuroshio Extension ◽  
Storm Track ◽  
Western Boundary ◽  
Atmospheric Variability ◽  
The North ◽  
The Kuroshio ◽  
The North Pacific

Abstract Coherent, large-scale shifts in the paths of the Gulf Stream (GS) and the Kuroshio Extension (KE) occur on interannual to decadal time scales. Attention has usually been drawn to causes for these shifts in the overlying atmosphere, with some built-in delay of up to a few years resulting from propagation of wind-forced variability within the ocean. However, these shifts in the latitudes of separated western boundary currents can cause substantial changes in SST, which may influence the synoptic atmospheric variability with little or no time delay. Various measures of wintertime atmospheric variability in the synoptic band (2–8 days) are examined using a relatively new dataset for air–sea exchange [Objectively Analyzed Air–Sea Fluxes (OAFlux)] and subsurface temperature indices of the Gulf Stream and Kuroshio path that are insulated from direct air–sea exchange, and therefore are preferable to SST. Significant changes are found in the atmospheric variability following changes in the paths of these currents, sometimes in a local fashion such as meridional shifts in measures of local storm tracks, and sometimes in nonlocal, broad regions coincident with and downstream of the oceanic forcing. Differences between the North Pacific (KE) and North Atlantic (GS) may be partly related to the more zonal orientation of the KE and the stronger SST signals of the GS, but could also be due to differences in mean storm-track characteristics over the North Pacific and North Atlantic.

scholarly journals Measuring the Impact of Observations on the Predictability of the Kuroshio Extension in a Shallow-Water Model

2012 ◽  
Vol 42 (1) ◽  
pp. 3-17 ◽  
Author(s):  
Werner Kramer ◽  
Henk A. Dijkstra ◽  
Stefano Pierini ◽  
Peter Jan van Leeuwen
Keyword(s):  
Shallow Water ◽  
Particle Filtering ◽  
Predictive Power ◽  
Kuroshio Extension ◽  
Water Model ◽  
Ensemble Prediction ◽  
Shallow Water Model ◽  
One Year ◽  
The Impact ◽  
The Kuroshio

Abstract In this paper, sequential importance sampling is used to assess the impact of observations on an ensemble prediction for the decadal path transitions of the Kuroshio Extension. This particle-filtering approach gives access to the probability density of the state vector, which allows the predictive power—an entropy-based measure—of the ensemble prediction to be determined. The proposed setup makes use of an ensemble that, at each time, samples the climatological probability distribution. Then, in a postprocessing step, the impact of different sets of observations is measured by the increase in predictive power of the ensemble over the climatological signal during one year. The method is applied in an identical-twin experiment for the Kuroshio Extension using a reduced-gravity shallow-water model. This study investigates the impact of assimilating velocity observations from different locations during the elongated and the contracted meandering states of the Kuroshio Extension. Optimal observation locations correspond to regions with strong potential vorticity gradients. For the elongated state the optimal location is in the first meander of the Kuroshio Extension. During the contracted state it is located south of Japan, where the Kuroshio separates from the coast.

“Eddy Resolving” Observation of the North Pacific Subtropical Mode Water

2011 ◽  
Vol 41 (4) ◽  
pp. 666-681 ◽  
Author(s):  
Eitarou Oka ◽  
Toshio Suga ◽  
Chiho Sukigara ◽  
Katsuya Toyama ◽  
Keishi Shimada ◽  
...  
Keyword(s):  
High Resolution ◽  
North Pacific ◽  
Kuroshio Extension ◽  
Uniform Structure ◽  
Mode Water ◽  
Subtropical Mode Water ◽  
The North ◽  
Late Fall ◽  
The Kuroshio ◽  
The North Pacific

Abstract Hydrographic data obtained by high-resolution shipboard observations and Argo profiling floats have been analyzed to study the mesoscale structure and circulation of the North Pacific Subtropical Mode Water (STMW). The float data show that in the late winter of 2008, STMW having a temperature of approximately 18.8°, 17.7°, and 16.6°C formed west of 140°E, at 140°–150°E, and east of 150°E, respectively, in the recirculation gyre south of the Kuroshio Extension. After spring, the newly formed STMW gradually shift southward, decreasing in thickness. Simultaneously, the STMWs of 16.6° and 17.7°C are gradually stirred and then mixed in terms of properties. In late fall, they seem to be integrated to form a single group of STMWs having a temperature centered at 17.2°C. Such STMW circulation in 2008 is much more turbulent than that in 2006, which was investigated in a previous study. The difference between the two years is attributed to the more variable state of the Kuroshio Extension in 2008, associated with stronger eddy activities in the STMW formation region, which enhance the eddy transport of STMW. High-resolution shipboard observations were carried out southeast of Japan at 141°–147°E in the early fall of 2008. To the south of the Kuroshio Extension, STMW exists as a sequence of patches with a horizontal scale of 100–200 km, whose thick portions correspond well to the mesoscale deepening of the permanent pycnocline. The western (eastern) hydrographic sections are occupied mostly by the 17.7°C (16.6°C) STMW, within which the 16.6°C (17.7°C) STMW exists locally, mostly at locations where both the permanent pycnocline depth and the STMW thickness are maximum. This structure implies that the STMW patches are transported away from their respective formation sites, corresponding to a shift in the mesoscale anticyclonic circulations south of the Kuroshio Extension. Furthermore, 20%–30% of the observed STMW pycnostads have two or three potential vorticity minima, mostly near temperatures of 16.6° and 17.7°C. The authors presume that such a structure formed as a result of the interleaving of the 16.6° and 17.7°C STMWs after they are stirred by mesoscale circulations, following which they are vertically mixed to form the 17.2°C STMW observed in late fall. These results indicate the importance of horizontal processes in destroying the vertically uniform structure of STMW after spring, particularly when the Kuroshio Extension is in a variable state.

scholarly journals Southward spreading of the Fukushima-derived radiocesium across the Kuroshio Extension in the North Pacific

2014 ◽  
Vol 4 (1) ◽  
Author(s):  
Yuichiro Kumamoto ◽  
Michio Aoyama ◽  
Yasunori Hamajima ◽  
Tatsuo Aono ◽  
Shinya Kouketsu ◽  
...  
Keyword(s):  
North Pacific ◽  
Kuroshio Extension ◽  
The North ◽  
The Kuroshio ◽  
The North Pacific
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