North Pacific Research Articles

Size Characteristics of Tropical Cyclones Affecting East China and Those in the Western North Pacific

Size Characteristics of Tropical Cyclones Affecting East China and Those in the Western North Pacific

Future changes in tropical cyclone tracks over the western North Pacific under climate change

The current study, leveraging large ensemble high-resolution atmospheric model simulations (d4PDF) with three warming scenarios, uncovers potential shifts in tropical cyclone (TC) tracks within the western North Pacific (WNP) under future warming. Both northward and eastward migrations are detected in projected TC tracks. TC tracks north of 40°N are projected to surge by 25% and 65%, respectively, under the future 2 K and 4 K warming scenarios. Meantime, TC tracks south of 40°N and east of 160°E are projected to increase by 15% and 36%, respectively, under the two warming scenarios. These changes in TC tracks are intimately linked to shifts in TC genesis locations and alterations in large-scale steering flows. Specifically, the increase in TC tracks north of 40°N is attributed to a slowdown of the TC movement due to slow-down of westerly steering flows. The increase in TC tracks east of 160°E is closely associated with the rise in TC genesis east of 160°E due to an anomalous cyclone. Additionally, there is a decrease in projected TC landfalling along the East Asian coast, predominantly attributable to the reduced TC genesis west of 160°E. Our findings emphasize the heightened vulnerability of high-latitude regions in China and Japan to TC hazards under future warming conditions.

Inefficient melt mixing below a fast-spreading ridge revealed by Hess Deep lower gabbros (ODP Leg 147 and IODP Expedition 345).

The oceanic crust crystallizes from melts formed within a heterogeneous mantle source, which is mostly composed of variably depleted peridotites and recycled crust. Yet, the compositional variability of this mantle source and the progressive aggregation of heterogeneous melts during extraction are poorly constrained. Here, we show that in situ isotopic analyses in gabbros formed at the East Pacific Rise retain substantially greater Sr-Nd-Hf isotopic heterogeneity than basalts erupted along the fast-spreading ridge. This implies that melt aggregation during migration through the upper mantle and lower crust is inefficient, even at magmatically productive spreading ridges; efficient melt mixing likely occurs in the overlying axial melt lens. Local isotopic heterogeneity of Hess Deep gabbros indicates incomplete mixing of primary melts produced from variably depleted peridotites and oceanic crust recycled at least 1.5billion years ago. The isotopic heterogeneity recorded in lower gabbros further substantiates that basalt compositions reflect only part of the compositional spectrum of melts passing through the ridge plumbing system.

Global relationship between upwelling intensities and mangrove distribution and area.

Global relationship between upwelling intensities and mangrove distribution and area.

Distinct Future Changes in the Mid-latitude and Low-latitude Connections between the South and East Asian Summer Monsoons Projected by CMIP6 Models

Abstract The South Asian summer monsoon (SASM) and the East Asian summer monsoon (EASM) are connected through two plausible pathways: a mid-latitude wave pattern and low-latitude coherent water vapor transport. To reveal their different responses to global warming, this study investigates their future changes using the moderate- and high-emissions Shared Socioeconomic Pathway 2-4.5 and 5-8.5 (SSP245 and SSP585) experiments from 26 models of the phase 6 of the Coupled Model Intercomparison Project. Results show that the mid-latitude connection is projected to be weakened while the low-latitude pathway is projected to be strengthened in both scenarios, with stronger changes in SSP585. The weakening mid-latitude pathway in future is likely attributed to the weakened climatological westerly jet stream. The weakening Northeast Asia anticyclone in the mid-latitude wave train suppresses water vapor transport and vertical motions to northern China, resulting in a weakened rainfall relationship between northern China and the SASM region. The low-latitude pathway is anticipated to be strengthened, probably due to the strengthened Maritime Continent summer rainfall. The strengthening western North Pacific anticyclone in the low-latitude moisture transport pathway increases the horizontal water vapor transport to the Yangtze River Valley but its northward shift suppresses local vertical motions, leading to a weakened relationship between the Yangtze River Valley and SASM rainfalls in both SSP245 and SSP585. Through separately analyzing the rainfall patterns associated with the two pathways and the underlying physical mechanisms, this study enhances our understanding of the future changes in the SASM-EASM relationship under global warming.

A multi-year, seasonally resolved dataset of Seaglider observations at Station ALOHA in the North Pacific Subtropical Gyre

We present a large, quality-controlled dataset consisting of autonomous underwater measurements of hydrographical (temperature, salinity, and pressure), chemical (dissolved oxygen concentration), and bio-optical (chlorophyll a concentration and particulate backscatter) properties. Data were collected using underwater gliders on 18 missions in the North Pacific Subtropical Gyre between 2008 and 2023 (>20,000 vertical profiles). Each mission was centered near the long-term sampling site of the Hawaii Ocean Time-series program, Station ALOHA (A Long-term Oligotrophic Habitat Assessment). Measurements were quality controlled and calibrated to provide a robust dataset, inter-comparable among missions. We compare depth-resolved seasonality of Seaglider observations to previously described seasonal climatologies at Station ALOHA from ship-based observations. Results show that underwater gliders can accurately characterize ocean physical and biogeochemical conditions, reconstruct seasonality, and observe spatial variability and stochastic events in the absence of extensive ship operations. Further, these data allow us to study the variability of features, such as the chlorophyll and oxygen subsurface maxima with a temporal resolution of a few hours during multiple months.

Role of ocean coupling in the weakening of the extratropical storm tracks from Arctic sea ice loss

Abstract Within the changing climate, the Northern Hemisphere storm tracks have been projected to shift poleward and expand eastward. Changes in the Northern Hemisphere storm tracks arise from a variety of sometimes competing effects on the region’s baroclinicity. Arctic amplification weakens the meridional temperature gradient, hence weakening the storm track, while low-latitude warming has the opposite effect, and surface-amplified warming at high latitudes reduces static stability. To determine the mechanisms driving these competing changes, we use a hierarchy of models with different levels of ocean–atmosphere coupling, using forcings from the Polar Amplification Model Intercomparison Project (PAMIP) to assess the role of Arctic sea ice loss on the Northern Hemisphere storm tracks. We find that ocean–atmosphere coupling enhances and sharpens the weakening of both the North Atlantic and North Pacific storm tracks in response to Arctic sea ice loss, that surface turbulent heat flux modulates the intensity of the weakening, and that local ocean dynamics controls the meridional location of the response. A moist isentropic diagnostic of the atmospheric overturning circulation shows that most of the weakening of the storm tracks and its associated changes in atmospheric heat transport (AHT) arise from a weakening of the transient eddy mass flux. Poleward of the storm tracks, the AHT also decreases, but through weakened effective stratification rather than weakening mass fluxes, an effect which occurs even in the absence of ocean dynamical coupling.

Seesaw of Tropical Cyclone Frequency between Eastern and Western Regions of the Western North Pacific

Abstract Because of the limited length of observed tropical cyclone (TC) data and low confidence in modeling TC genesis frequency, it has been difficult to understand why the genesis frequency of global TCs has remained nearly invariant while regional variations are highly pronounced. Investigating the covariability of TC genesis frequency between different regions may shed light on this question. Here, we identify that TC genesis frequency varies out of phase between the eastern and western regions of the western North Pacific (WNP). Such a seesaw relationship could be explained by the east–west dipole patterns of low-level vorticity and midtropospheric relative humidity in the WNP, associated with variations in atmospheric conditions. Composite analyses and numerical experiments show that a combination of cooling in the WNP and warming in the north Indian Ocean (NIO) exerts a significant influence on the seesaw pattern. Our study adds more evidence to believe on number conservation of worldwide TC genesis. Significance Statement Little had been known about why the genesis frequency of global tropical cyclones has remained nearly invariant in a changing climate. To find out whether there is any covariability of tropical cyclone genesis frequency between different regions may provide a chance to understand such a steady trend. The western North Pacific is the ocean basin where tropical cyclones are the most active in the world. In this study, it is observed that tropical cyclone genesis frequency between the eastern and western regions of the western North Pacific has a negative correlation. It is demonstrated that the zonal contrast of sea surface temperature in the western North Pacific to the north Indian Ocean plays a significant role in driving the seesaw relationship of tropical cyclone genesis frequency by moderating the large-scale atmospheric circulation.

Interdecadal Change of Relationship between North Atlantic Oscillation and Tropical Cyclone Genesis Frequency over the Western North Pacific

Abstract This article investigates the relationship between spring (March–May) North Atlantic Oscillation (NAO) and the tropical cyclone genesis frequency (TCGF) over the western North Pacific (WNP) from June to November. It is found that their relationship appears insignificant from 1950 to 1971, intensifies significantly from 1972 to 2010, and then weakens again since 2011. The interdecadal change of this relationship is strongly influenced by the meridional displacement of the North Atlantic jet stream (NAJS). During 1972–2010, the NAJS is located southward, facilitating the spread of Rossby wave energy to the equatorial region and enhancing the NAO impact on sea surface temperatures (SSTs) over the tropical North Atlantic (TNA). Generally, positive (negative) phases of the NAO relate to negative (positive) TNA SST anomalies in spring, subsequently triggering positive (negative) SST anomalies in the central Pacific through the wind–evaporation–SST feedback. The central Pacific SST anomalies, intensifying from summer to autumn, lead to a basin-uniform circulation anomaly over the WNP and ultimately control the WNP TCGF. Conversely, in the other two periods, owing to the northward shift of the NAJS, the influence of the NAO is constrained to the extratropics, thereby disrupting the linkage between the NAO and TNA SST anomalies. As a result, the interannual relationship of spring NAO with the WNP TCGF weakens. The decadal meridional shift of the NAJS is supposed to be associated with the phase transition of the Pacific decadal oscillation. Significance Statement To enhance the understanding of the relationship between tropical cyclones and mid- to high-latitude climate systems, we explore how the North Atlantic Oscillation affects the genesis frequency of tropical cyclones in the western North Pacific and why their relationship encounters interdecadal changes. We propose that the North Atlantic Oscillation can trigger sea surface temperature anomalies over the tropical North Atlantic during spring, which subsequently affect the tropical cyclone formation over the western North Pacific in summer and autumn. Importantly, this relationship experiences interdecadal changes, aligning with changes in the meridional shift of the North Atlantic jet stream which may be related to the phase change of the Pacific decadal oscillation. Understanding these dynamics is crucial for climate predictions and addressing the potential impacts of extratropical systems on tropical cyclones.

Intercomparison of bias of global sea surface temperature products associated with tropical cyclone passages in the western North Pacific

Intercomparison of bias of global sea surface temperature products associated with tropical cyclone passages in the western North Pacific

A New Species of the Eel Genus Gnathophis (Congridae, Anguilliformes) from the Seamounts of the Emperor–Hawaiian Chain, Western and Central North Pacific

Gnathophis johnsoni sp. nov. is described on the basis of 15 specimens (138–380 mm TL) from the Emperor–Hawaiian Seamount Chain in the western and central North Pacific. The new species is most similar in morphology to G. bathytopos (Atlantic), G. cinctus (eastern Pacific), and G. smithi (Nazca and Salas-y-Gomez Seamounts in the southeastern Pacific) by the sensory pore configuration and vertebral count, but differs from these species in the following characters in combination: darkly pigmented pectoral fin, dorsal fin with black margin broadened caudally and extended onto the distal half of the caudal fin, relatively long head, jaws, gill slit and caudal fin, and on average a greater preanal distance. Although most of morphometrics overlap between the new species and its closest relatives, multivariate statistical analyses clearly discriminate this species. Molecular analysis shows sister relationships between the new species and G. cinctus, with 1.81% of genetic divergence, which significantly exceeds the differences between the haplotypes belonging to the same species (0.36 and 1.08% of divergence, usually not exceeding 0.9%) and confirms both species as close but distinct. The close relationship of G. johnsoni sp. nov. and G. cinctus represents a rare case of biogeographical relations between western and eastern Pacific demersal fish faunas. Molecular data suggest that some morphologically similar species may represent independently evolved lineages, though the group of Gnathophis possessing elevated lateral-line pores is likely monophyletic.

Reconsideration of Parapatric Distribution Between Pacific Saury (Cololabis saira) and Japanese Sardine (Sardinops melanostictus) in the Western North Pacific Ocean: Comparisons of Two Long‐Term Field Survey Results

ABSTRACTPacific saury (Cololabis saira) and the Pacific stock of Japanese sardine (Sardinops melanostictus) are dominant small pelagic fishes and are targeted by international fisheries in the western North Pacific (WNP). Using monitoring results of a pelagic trawl survey during 2003–2019 in WNP and central North Pacific, a previous study detected a shift in the center of distribution along sea surface temperature gradient (GT) of saury only in WNP, together with “parapatric” horizontal distribution between the two species during the 2010s, when saury biomass declined and sardine biomass increased. Thus, it suggested biological interactions between the two species. To corroborate this “parapatric” distribution, we applied basically the identical statistical analyses to driftnet survey results along longitudinal transects at 155°E, 170°E, and 175.5°E during 1979–1999, when saury stock was abundant and sardine stock declined since 1989. Our results indicated GT of saury slightly shifted after 1989 at 155°E, and spatial distribution of the two species largely overlapped before 1989, which do not support the previous study. While saury biomass drastically declined in the western areas of their overall distribution since 2003 and age‐0 sardine dominated in the pelagic trawl survey, age‐0 sardine occupied the southern area of overall distribution in the driftnet survey. These observations suggest that interspecies interactions between saury and sardine, if existed, are unlikely to take a form of parapatry. The apparent parapatric distribution can be explained by different age compositions of sardine between the two surveys and biomass‐derived eastward shrinkage of saury distribution since 2003.

The Stratospheric Polar Vortex and Surface Effects: The Case of the North American 2018/19 Cold Winter

A severe cold air outbreak hit the US and parts of Canada in January 2019, leaving behind many casualties where at least 21 people died as a consequence. According to Insurance Business America, the event cost the US about 1 billion dollars. In the Midwest, surface temperatures dipped to the lowest on record in decades, reaching −32 °C in Chicago, Illinois, and down to −48 °C wind chill temperature in Cotton and Dakota, Minnesota, giving rise to broad media attention. A zonal wavenumber 1–3 planetary wave forcing caused a sudden stratospheric warming, with a displacement followed by a split of the polar vortex at the beginning of 2019. The common downward progression of the stratospheric anomalies stalled at the tropopause and, thus, they did not reach tropospheric levels. Instead, the stratospheric trough, developing in a barotropic fashion around 70° W, turned the usually baroclinic structure of the Aleutian high quasi-barotropic. In response, upward propagating waves over the North Pacific were reflected at its lower stratospheric, eastward tilting edge toward North America. Channeled by a dipole structure of positive and negative eddy geopotential height anomalies, the waves converged at the center of the latter and thereby strengthened the circulation anomalies responsible for the severely cold surface temperatures in most of the Midwest and Northeast US.

A new species of the thorid shrimp genus Heptacarpus Holmes, 1900 (Decapoda: Caridea) from Japan

The thorid shrimp genus Heptacarpus Holmes, 1900 is currently represented by 34 species (De Grave & Fransen 2011; Komai 2023; DecaNet 2025). These species are exclusively found in the North Pacific, inhabiting various environments from coastal waters to the continental slope, reaching depths of up to 1580 m (Hayashi 1979; Butler 1980; Wicksten 1990; Komai & Ivanov 2008; Komai & Komatsu 2009). From East Asian waters, 16 species have been recorded, of which 13 species are restricted to the area (Hayashi 1979, 1992; Hayashi & Chiba 1987, 1989; Komai & Ivanov 2008; Kim 2012; Xu & Li 2015; Komai 2023). During a study of material dredged from the coastal waters south of Izu Peninsula, central Japan, two specimens somewhat resembling Heptacarpus geniculatus (Stimpson, 1860) and H. longirostris (Kobjakova, 1936), were found. Through a combination of morphological comparison and phylogenetic analysis utilizing the mitochondrial 16S rRNA gene, the study uncovered a previously unknown species. Here the new species, H. elatus, is described and illustrated.

Decadal-scale reduction in net primary production in the western subarctic North Pacific: impact of lateral transport of dissolved iron from the Sea of Okhotsk

Decadal-scale reduction in net primary production in the western subarctic North Pacific: impact of lateral transport of dissolved iron from the Sea of Okhotsk

Evidence for crustal brines and deep fluid infiltration in an oceanic transform fault.

Although oceanic transform faults (OTFs) are ubiquitous plate boundaries, the geological processes occurring along these systems remain underexplored. The Gofar OTF of the East Pacific Rise has gained attention due to its predictable, yet enigmatic, earthquake cycle. Here, we present results from the first ever controlled-source electromagnetic survey of an OTF, which sampled Gofar. We find that the fault is characterized by a subvertical conductor, which extends into the lower crust and thus implies deep fluid penetration. We also image subhorizontal crustal conductors distributed asymmetrically about the fault. We interpret these subhorizontal anomalies as crustal brines, and we suggest that the high permeability of the fault combined with the influence of melt in the transform domain can promote hydrothermal circulation and brine condensation at OTFs.

A Sandwich‐Like Pattern of Eastern China Summer Precipitation Change Projected by CMIP6 Models

ABSTRACTA reliable projection of the summer (June–August) mean precipitation over eastern China (EC) in the future is crucial for climate adaptation activities in this densely populated region. In contrast to existing studies, which have primarily focused on the EC mean precipitation change and have demonstrated a wetting trend in the future, this study, based on an analysis of 35 Coupled Model Intercomparison Project Phase 6 models, highlights that the future precipitation rise within the EC area is distributed inhomogeneously with latitudes. The southern and northern EC regions are projected to experience a pronounced increase in precipitation, while the middle EC, where the well‐known meiyu‐baiu rainbelt is located, is expected to witness a comparatively weaker rise. This sandwich‐like pattern is consistent across models and is evident irrespective of future periods and greenhouse‐gas‐emission scenarios specified. The findings have significant implications for the future management of water resources along China's major rivers, which are all located within the EC. Further analysis of the moisture budget indicates that the dynamical response to global warming is the key driver of this sandwich‐like pattern of precipitation change. The relatively weak precipitation increase over the central EC is attributed to the eastward retreat of the western North Pacific subtropical high (WNPSH) in the future, while a more pronounced precipitation increase over the northern EC is related to the enhanced southerly wind along the eastern coast of China.

Optimizing Topographic Boundary Conditions for East Pacific Climate Simulation

Abstract Overly-smooth topography in general circulation models (GCMs) underestimates the blocking effect of the steep mountain ranges flanking the eastern Pacific. We explore the impact of this bias on common biases in Pacific climate simulation (i.e. the unrealistic cross-equatorial symmetry of near-surface winds, sea surface temperatures (SST), and precipitation) through sensitivity experiments with modified Central and/or South American topography in an atmosphere-ocean coupled GCM. Quantifying orographic blocking potential via the Froude number, we determine that an envelope topographic interpolation scheme best captures observed blocking patterns. Implementing envelope topography only in Central America reduced model biases as greater blocking of the trade winds warmed SST and enhanced convergence in the northeastern Pacific. Doing so additionally over the Andes improved the simulation of south Pacific circulation and the South Pacific Convergence Zone as stronger deflection of the westerlies intensified the South Pacific Anticyclone. This mitigated convection biases in the southeast Pacific by increasing subsidence and cooling SST, however, remote impacts of the Andes exacerbated the dry bias in the northeast tropical Pacific, resulting in negligible improvement in the east Pacific double-ITCZ. We find that, due to the significant role of large-scale convergence in driving precipitation patterns, other model biases, such as cloud-radiative biases, may modulate the impact of altering topography. Our results highlight the importance of considering alternate methods for calculating model topographic boundary conditions, though the optimal interpolation scheme will vary with model resolution and the impact of topography on GCM biases can be sensitive to choices made in formulating parameterizations.

Variability of Autumn Tropical Pacific Yellowfin Tuna Tied to the Spring North Atlantic Tripole

AbstractClimate change affects the spatial distribution and abundance of yellowfin tuna (Thunnus albacares, YFT) in the tropical Pacific, yet the mechanisms linking remote climate modes to YFT dynamics remain unclear. This study finds that the variability of autumn tropical Pacific YFT is tied to the spring sea surface temperature anomalies (SSTAs) of the North Atlantic Tripole (NAT), mediated by the Victoria Mode (VM), the second dominant mode of North Pacific SSTAs variability. The result shows that the spring NAT is significantly positive correlated with the subsequent autumn tropical Pacific YFT catch per unit effort (CPUE). The spring NAT triggers eastward‐propagating Rossby waves, inducing VM‐like SSTAs in the North Pacific. These anomalies modify YFT habitat conditions in the tropical Pacific through coupled oceanic‐atmospheric bridge (COAB) mechanism, ultimately affecting autumn CPUE. This study unveils a teleconnection‐driven mechanism influencing tropical Pacific YFT CPUE, with important implications for fisheries management and forecasting.

Revisiting the distribution and total amount of nitrogen fixation across the Kuroshio

AbstractThe Kuroshio Current, a western boundary current in the North Pacific Ocean, is regarded as a hotspot of nitrogen fixation that drives marine primary productivity and biogeochemical cycles. However, this assumption is based on limited, spatiotemporally biased data. We curated nitrogen fixation data and applied a generalized additive model to revisit the distribution and total amount of nitrogen fixation in the Kuroshio region. We found a substantial spatial variation, with lower nitrogen fixation in southern Japan and higher rates in the more upstream areas. These variations were explained by nitrate concentration, sea surface temperature, and the distance along the Kuroshio from its origin. We calculated the total nitrogen fixation for the Kuroshio region to be approximately half of the previous estimate. This study provides a more precise estimate of the regional nitrogen fixation and highlights its biogeochemical importance in the Kuroshio region and the western North Pacific Ocean.