Western Tropical Pacific Ocean Research Articles

The Interannual Variability of the Haines Index over North America

AbstractThe Haines index (HI) is a fire-weather index that is widely used as an indicator of the potential for dry, low-static-stability air in the lower atmosphere to contribute to erratic fire behavior or large fire growth. This study examines the interannual variability of HI over North America and its relationship to indicators of large-scale circulation anomalies. The results show that the first three HI empirical orthogonal function modes are related respectively to El Niño–Southern Oscillation (ENSO), the Arctic Oscillation (AO), and the interdecadal sea surface temperature variation over the tropical Pacific Ocean. During the negative ENSO phase, an anomalous ridge (trough) is evident over the western (eastern) United States, with warm/dry weather and more days with high HI values in the western and southeastern United States. During the negative phase of the AO, an anomalous trough is found over the western United States, with wet/cool weather and fewer days with high HI, while an anomalous ridge occurs over the southern United States–northern Mexico, with an increase in the number of days with high HI. After the early 1990s, the subtropical high over the eastern Pacific Ocean and the Bermuda high were strengthened by a wave train that was excited over the tropical western Pacific Ocean and resulted in warm/dry conditions over the southwestern United States and western Mexico and wet weather in the southeastern United States. The above conditions are reversed during the positive phase of ENSO and AO and before the early 1990s.

Dimethylsulphide (DMS) emissions from the western Pacific Ocean: a potential marine source for stratospheric sulphur?

Abstract. Sea surface and atmospheric measurements of dimethylsulphide (DMS) were performed during the TransBrom cruise in the western Pacific Ocean between Japan and Australia in October 2009. Air–sea DMS fluxes were computed between 0 and 30 μmol m−2 d−1, which are in agreement with those computed by the current climatology, and peak emissions of marine DMS into the atmosphere were found during the occurrence of tropical storm systems. Atmospheric variability in DMS, however, did not follow that of the computed fluxes and was more related to atmospheric transport processes. The computed emissions were used as input fields for the Lagrangian dispersion model FLEXPART, which was set up with actual meteorological fields from ERA-Interim data and different chemical lifetimes of DMS. A comparison with aircraft in situ data from the adjacent HIPPO2 campaign revealed an overall good agreement between modelled versus observed DMS profiles over the tropical western Pacific Ocean. Based on observed DMS emissions and meteorological fields along the cruise track, the model projected that up to 30 g S per month in the form of DMS, emitted from an area of 6 × 104 m2, can be transported above 17 km. This surprisingly large DMS entrainment into the stratosphere is disproportionate to the regional extent of the area of emissions and mainly due to the high convective activity in this region as simulated by the transport model. Thus, if DMS can cross the tropical tropopause layer (TTL), we suggest that the considerably larger area of the tropical western Pacific Ocean can be a source of sulphur to the stratosphere, which has not been considered as yet.

Ocean Warming Effect on Surface Gravity Wave Climate Change for the End of the Twenty-First Century

Abstract Surface wind (U10) and significant wave height (Hs) response to global warming are investigated using a coupled atmosphere–wave model by perturbing the sea surface temperatures (SSTs) with anomalies generated by the Working Group on Coupled Modeling (WGCM) phase 3 of the Coupled Model Intercomparison Project (CMIP3) coupled models that use the Intergovernmental Panel on Climate Change Fourth Assessment Report (IPCC AR4)/Special Report on Emissions Scenarios A1B (SRES A1B) scenario late in the twenty-first century. Several consistent changes were observed across all four realizations for the seasonal means: robust increase of U10 and Hs in the Southern Ocean for both the austral summer and winter due to the poleward shift of the jet stream; a dipole pattern of the U10 and Hs with increases in the northeast sector and decreases at the midlatitude during boreal winter in the North Atlantic due to the more frequent occurrence of the positive phases of the North Atlantic Oscillation (NAO); and strong decrease of U10 and Hs in the tropical western Pacific Ocean during austral summer, which might be caused by the joint effect of the weakening of the Walker circulation and the large hurricane frequency decrease in the South Pacific. Changes of the 99th percentile U10 and Hs are twice as strong as changes in the seasonal means, and the maximum changes are mainly dominated by the changes in hurricanes. Robust strong decreases of U10 and Hs in the South Pacific are obtained because of the large hurricane frequency decrease, while the results in the Northern Hemisphere basins differ among the models. An additional sensitivity experiment suggests that the qualitative response of U10 and Hs is not affected by using SST anomalies only and maintaining the radiative forcing unchanged (using 1980 values), as in this study.

Thermohaline intrusions in the thermocline of the western tropical Pacific Ocean

The existing high-resolution hydrographic data in the western tropical Pacific Ocean are used to explore the spatial distribution and primary characteristics of thermohaline intrusions in the thermocline. Statistics show that the vertical scales of intrusions are 20-40 m in the upper thermocline (22.0-26.0 sigma(0)) and 40-80 m in the lower thermocline (26.0-27.2 sigma(0)). In the upper thermocline, the most intensive intrusions exist at the equatorial front (EF) where north/south Pacific water masses converge, and the westward spreading of the north Pacific tropical water (NPTW) in the Philippines Sea also produces patches of intrusions surrounding its high-salinity tongue. In the lower thermocline, intrusions are also strong at the tropical front (TF) which is the boundary between the north Pacific subtropical/tropical waters. At the bottom of the thermocline (at about 27.0 sigma(0)), intrusions mainly exist near the western boundary, which are produced by intermediate water convergence through the advection of subthermocline western boundary flows. Most strikingly a "C"-shape distribution of intrusions at around 26.4 sigma(0) is revealed, covering the vicinity of the EF, the TF, and the Mindanao Current (MC), i.e., the western boundary pathway of the north Pacific subtropical cell (STC). Synoptic section analysis reveals that intrusions are more prominent on the warm/salty flank of the fronts, implying more cross-front tongues of cold/fresh water. Among the intrusions, those at the EF are of best lateral coherence which implies a unique driving mechanism involving near-inertial velocity perturbations near the equator.

Holocene climatic reconstructions from the fossil pollen record at Qigai Nuur in the southern Mongolian Plateau

This study focuses on the reconstructions of vegetation and climate changes during the past ~11,000 years on the basis of 222 fossil pollen samples from Qigai Nuur (core QGN-2004) in the southern part of the Mongolian Plateau. Plant Functional Type – Modern Analogue Technique was used for quantitative climatic reconstructions from fossil pollen data. Our results showed that regional vegetation experienced dramatic shifts between steppe forest and dry steppe before 9200 cal. yr BP in the Qigai Nuur region. The reconstructed mean annual temperature and especially mean annual precipitation also showed fluctuations at that time. From ~9200 to ~2800 cal. yr BP, the vegetation was dominated by steppe forests, and the reconstructed climate was generally warm and wet, but with two cold and dry intervals at ~7400 to ~6000 cal. yr BP and at ~4000 to ~2800 cal. yr BP. From ~2800 to ~850 cal. yr BP, dry steppe vegetation dominated the landscape under slightly cooler and much drier climate conditions. During the past ~850 years, the vegetation was characterized by abundant herbs and the climate showed rising temperature and fluctuating precipitation. The comparison of the reconstructed precipitation from the Qigai Nuur core with monsoon-strength records from southern China shows that the first-order variation in the precipitation was most likely controlled by the summer insolation-dictated Inter-Tropical Convergence Zone movements (i.e. N–S shifts). The comparison of the reconstructed precipitation from Qigai Nuur core with surface sea temperature in the Western Tropical Pacific Ocean suggests that the second-order variation in the precipitation was most likely modulated by the El Niño-Southern Oscillation dynamics (i.e. E–W shifts).

Global ocean surface velocities from drifters: Mean, variance, El Niño–Southern Oscillation response, and seasonal cycle

Global near‐surface currents are calculated from satellite‐tracked drogued drifter velocities on a 0.5° × 0.5° latitude‐longitude grid using a new methodology. Data used at each grid point lie within a centered bin of set area with a shape defined by the variance ellipse of current fluctuations within that bin. The time‐mean current, its annual harmonic, semiannual harmonic, correlation with the Southern Oscillation Index (SOI), spatial gradients, and residuals are estimated along with formal error bars for each component. The time‐mean field resolves the major surface current systems of the world. The magnitude of the variance reveals enhanced eddy kinetic energy in the western boundary current systems, in equatorial regions, and along the Antarctic Circumpolar Current, as well as three large “eddy deserts,” two in the Pacific and one in the Atlantic. The SOI component is largest in the western and central tropical Pacific, but can also be seen in the Indian Ocean. Seasonal variations reveal details such as the gyre‐scale shifts in the convergence centers of the subtropical gyres, and the seasonal evolution of tropical currents and eddies in the western tropical Pacific Ocean. The results of this study are available as a monthly climatology.

Asynchronous marine-terrestrial signals of the last deglacial warming in East Asia associated with low- and high-latitude climate changes

A high-resolution multiproxy record, including pollen, foraminifera, and alkenone paleothermometry, obtained from a single core (DG9603) from the Okinawa Trough, East China Sea (ECS), provided unambiguous evidence for asynchronous climate change between the land and ocean over the past 40 ka. On land, the deglacial stage was characterized by rapid warming, as reflected by paleovegetation, and it began ca. 15 kaBP, consistent with the timing of the last deglacial warming in Greenland. However, sea surface temperature estimates from foraminifera and alkenone paleothermometry increased around 20-19 kaBP, as in the Western Pacific Warm Pool (WPWP). Sea surface temperatures in the Okinawa Trough were influenced mainly by heat transport from the tropical western Pacific Ocean by the Kuroshio Current, but the epicontinental vegetation of the ECS was influenced by atmospheric circulation linked to the northern high-latitude climate. Asynchronous terrestrial and marine signals of the last deglacial warming in East Asia were thus clearly related to ocean currents and atmospheric circulation. We argue that (i) early warming seawater of the WPWP, driven by low-latitude insolation and trade winds, moved northward via the Kuroshio Current and triggered marine warming along the ECS around 20-19 kaBP similar to that in the WPWP, and (ii) an almost complete shutdown of the Atlantic Meridional Overturning Circulation ca. 18-15 kaBP was associated with cold Heinrich stadial-1 and delayed terrestrial warming during the last deglacial warming until ca. 15 kaBP at northern high latitudes, and hence in East Asia. Terrestrial deglacial warming therefore lagged behind marine changes by ca. 3-4 ka.

Sulphur compounds, methane, and phytoplankton: interactions along a north–south transit in the western Pacific Ocean

Abstract. Here we present results of the first comprehensive study of sulphur compounds and methane in the oligotrophic tropical western Pacific Ocean. The concentrations of dimethylsuphide (DMS), dimethylsulphoniopropionate (DMSP), dimethylsulphoxide (DMSO), and methane (CH4), as well as various phytoplankton marker pigments in the surface ocean were measured along a north–south transit from Japan to Australia in October 2009. DMS (0.9 nmol L−1), dissolved DMSP (DMSPd, 1.6 nmol L−1) and particulate DMSP (DMSPp, 2 nmol L−1) concentrations were generally low, while dissolved DMSO (DMSOd, 4.4 nmol L−1) and particulate DMSO (DMSOp, 11.5 nmol L−1) concentrations were comparably enhanced. Positive correlations were found between DMSO and DMSP as well as DMSP and DMSO with chlorophyll a, which suggests a similar source for both compounds. Similar phytoplankton groups were identified as being important for the DMSO and DMSP pool, thus, the same algae taxa might produce both DMSP and DMSO. In contrast, phytoplankton seemed to play only a minor role for the DMS distribution in the western Pacific Ocean. The observed DMSPp : DMSOp ratios were very low and seem to be characteristic of oligotrophic tropical waters representing the extreme endpoint of the global DMSPp : DMSOp ratio vs SST relationship. It is most likely that nutrient limitation and oxidative stress in the tropical western Pacific Ocean triggered enhanced DMSO production leading to an accumulation of DMSO in the sea surface. Positive correlations between DMSPd and CH4, as well as between DMSO (particulate and total) and CH4, were found along the transit. We conclude that DMSP and DMSO and/or their degradation products might serve as potential substrates for CH4 production in the oxic surface layer of the western Pacific Ocean.

Sensitivity of summer precipitation to tropical sea surface temperatures over East Asia in the GRIMs GMP

AbstractIn this study, uncoupled atmospheric general circulation model experiments are conducted to examine the sensitivity of tropical Ocean basins from the Indian Ocean to the tropical Pacific Ocean on the summer precipitation variability over East Asia. It is remarkable that the Indian Ocean basin sea surface temperature (SST) and the tropical Pacific basin SST act on summer precipitation variability over Northeast Asia and southern China quite differently. That is, SST warming in the Indian Ocean largely contributes to the increase in the amount of summer precipitation over East Asia, which is in contrast to the warming of the western tropical Pacific Ocean. Our further analysis indicates that an altered large‐scale atmospheric circulation over the western tropical Pacific contributes to contrasting atmospheric motion over East Asia due to the tropics‐East Asia teleconnections, which results in changes in the amount of summer precipitation due to the warming of the Indian and western tropical Pacific Oceans.

Climate change simulated by full and mixed-layer ocean versions of CSIRO Mk3.5 and Mk3.0: The Asia-Pacific region

The patterns of climate change in the Asia-Pacific region simulated by versions of the CSIRO Mk3.5 and Mk3.0 climate models are examined and compared with those from 23 CMIP3 models. Using fields standardized by global warming, it is seen that both CSIRO coupled models simulate larger surface warming in the tropical western Pacific Ocean, and smaller warming in the eastern Indian Ocean, than the CMIP3 average, and also model versions with a mixed-layer ocean. Corresponding differences in the changes in the pressure, winds, rainfall and other quantities were simulated. Introducing the coupled Mk3.5’s sea surface temperature field for the present climate, which has a warm bias, as the base climate for the MLO version had only a minor effect on the MLO version’s pattern of climate change. A Pacific-Indian Dipole index quantifying the amplitude of the warming pattern explains much of the variation in rainfall change simulated by the CMIP3 models over Australia and the Indonesian and Melanesian regions. It relates more strongly to Australian average rainfall than several other indices representing southern hemispheric circulation changes. The decline in Australian rainfall produced by the full ocean coupling is largest in summer, but occurs in each season, and extends across the continent. Further assessment of the importance of the dipole change pattern in new simulations is warranted. Analyses aimed at reducing the uncertainty in its potential amplitude could help narrow the range of projections for change in the Australasian region.

Tree‐ring‐based annual precipitation reconstruction for the Hexi Corridor, NW China: consequences for climate history on and beyond the mid‐latitude Asian continent

An annual (July to June) precipitation reconstruction for the period AD 1760–2010 was developed from a Picea crassifolia regional tree‐ring chronology from two sites in the northern mountainous region of the Hexi Corridor, NW China. This reconstruction explains 52.1% of the actual precipitation variance during the period 1951 to 2010. Spatial correlations with gridded land‐surface data reveal that our reconstruction contains a strong regional precipitation signal for the Hexi Corridor and for the southern margin of the Badain Jaran Desert. Significant spectral peaks were identified at 31.9, 11.1, 8.0, 7.0, 3.2, 2.6 and 2.2 years. A large‐scale comparison indicates that our reconstruction is more consistent with climate records of a Westerly‐dominated Central Asia, and that the Westerlies have a greater impact on the precipitation in this region than the Asian summer monsoon. Our reconstructed precipitation series is significantly correlated with sea‐surface temperature (SST) in the tropical Atlantic Ocean (positive), the tropical Indian Ocean (positive), the western tropical Pacific Ocean (positive), and the western North Pacific Ocean (negative). The spatial correlation patterns between our precipitation reconstruction and SSTs of the Atlantic and Pacific Oceans suggest a connection between regional precipitation variations and the high‐mid‐latitude northern atmospheric circulations (Westerlies and Asian summer monsoon).

A Climatology of Surface Cloud Radiative Effects at the ARM Tropical Western Pacific Sites

AbstractCloud radiative effects on surface downwelling fluxes are investigated using datasets from the Atmospheric Radiation Measurement Program (ARM) sites in the tropical western Pacific Ocean (TWP) region. The Nauru Island (Republic of Nauru) and Darwin, Australia, sites show large variability in sky cover, downwelling radiative fluxes, and surface cloud radiative effect (CRE) that is due to El Niño–Southern Oscillation (ENSO) and the Australian monsoon, respectively, whereas the Manus Island (Papua New Guinea) site shows little intraseasonal or interannual variability. At Nauru, the average shortwave (SW) surface CRE varies from −38.2 W m−2during La Niña conditions to −90.6 W m−2during El Niño conditions. The average longwave (LW) CRE ranges from 9.5 to 15.8 W m−2during La Niña and El Niño conditions, respectively. At Manus, the average SW and LW CREs vary by less than 5 and 2 W m−2, respectively, between the ENSO phases. The variability at Darwin is even larger than at Nauru, with average SW (LW) CRE ranging from −27.0 (8.6) W m−2in the dry season to −95.8 (17.0) W m−2in the wet season. Cloud radar measurements of cloud-base and cloud-top heights are used to define cloud types to examine the effect of cloud type on the surface CRE. Clouds with low bases contribute 71%–75% of the surface SW CRE and 66%–74% of the surface LW CRE at the three TWP sites, clouds with midlevel bases contribute 8%–9% of the SW CRE and 12%–14% of the LW CRE, and clouds with high bases contribute 16%–19% of the SW CRE and 15%–21% of the LW CRE.

Origins of heat and freshwater anomalies underlying regional decadal sea level trends

AbstractRegional sea level changes often differ from global mean changes due to geographic variations in surface fluxes and to changes in ocean circulation. Here we study such regional sea level trends from 1993 to 2004 using a synthesis of observations and an ocean general circulation model. Unlike the global mean, steric changes dominate regional trends with negligible contributions from column‐integrated mass variations. Regional heat and freshwater anomalies underlying steric changes are in turn distinguished between redistribution of pre‐existing anomalies within the ocean and contributions from additional surface fluxes external to the ocean. Internal redistribution accounts for most regional trends but exceptions are found, most notably in the western tropical Pacific Ocean where a warming of external origin dominates the trend. On average, external thermosteric sea level trends are found to be positive in temperate regions while negative at higher latitudes with opposite trends found in halosteric anomalies of external origin.

Supercooling points and heat coma temperatures in four species of oceanic sea skaters of the genus Halobates (Heteroptera: Gerridae: Halobatinae)

The only insects known to live in the open ocean are several species of sea skaters of the genus Halobates (Heteroptera: Gerridae). We have collected four species in the tropical western Pacific Ocean and measured heat coma temperature (HCT) and supercooling point (SCP) in 132 specimens. The SCPs were relatively low (ranging between −18°C and −19°C) and similar in all species. Significant inter-species differences were found in the level of HCT. The lowest HCT 32.9°C was found in Halobates micans Eschscholtz, 1822, which is distributed in thermally stable tropical waters. The highest HCT levels of 36.6°C and 36.0°C were observed in Halobates sericeus Eschscholtz and Halobates germanus White, 1883, respectively, mostly occurring in thermally more fluctuating habitats (subtropical and warm temperate waters, and coastal waters, respectively). A new species, H. sp. (under process of description) showed an intermediate HCT of 34.8°C. In addition, we found significant negative statistical correlation between HCT and SCP values at the species and individual levels. We discuss our results in the light of putative relationship between thermal physiology of sea skaters and their distribution.

Observed Evolution of Northward-Propagating Intraseasonal Variation over the Western Pacific: A Case Study in Boreal Early Summer

Abstract This report describes the in situ observed evolution of the atmospheric profile during an event of the boreal summer intraseasonal variation (BSISV) in the tropical western Pacific Ocean. The convectively active region of the BSISV proceeded northward over the sounding and radar network. Over the array, the situation changed from a convectively inactive period to an active period. Inspection of the sounding data revealed the gradual moistening of the lower troposphere during the convectively inactive period. The sounding-derived heat and moisture budget analyses indicated that both the convective- and large-scale processes caused moistening of the lower and middle troposphere where the radar echo tops were observed most frequently. This study is the first to identify such a “preconditioning” process for the BSISV in the western Pacific using detailed in situ observational data. During the preconditioning, an increase in CAPE was observed, as in previous studies of the MJO. An increase of moisture in the boundary layer was responsible for the increase of CAPE. The large-scale horizontal convergence in the boundary layer may be a key factor to moisten the boundary layer through the convective-scale processes, as well as through the large-scale processes to moisten the lower and middle troposphere.

A numerical simulation of the impact of tropical western pacific sst anomalies on the decadal shift of the meiyu belt

The sea surface temperature (SST) of the tropical western Pacific Ocean (TWPO) showed a pronounced warming in the late 1990s. Using numerical experiments of a regional climate model (RegCM), we analyzed the impact of this warming on rainfall over the Yangtze-Huaihe River valley of China during the Meiyu period (June–July). The model results revealed that the observed decadal changes in Meiyu rainfall since the late 1990s can be reproduced by a control experiment forced by the observed SST. Additionally, the sensitivity experiments suggested that the warming trend in the TWPO played a substantial role in the northward shift of the Meiyu belt in the late 1990s.

Test of the Fixed Anvil Temperature Hypothesis

Abstract The fixed anvil temperature (FAT) hypothesis is examined based on the Aqua Moderate Resolution Imaging Spectroradiometer (MODIS)-based cloud-top temperature (CTT) in conjunction with the tropical atmospheric profiles and sea surface temperature (SST) from the European Centre for Medium-Range Weather Forecasts (ECMWF) Interim Reanalysis. Consistent with the physical governing mechanism of the FAT hypothesis, the peak clear-sky diabatic subsidence and convergence profiles are located at roughly the same level (200 hPa) as the peak in the cloud profile, which is fundamentally determined by the rapid decrease of water vapor concentration above this level. The geographical maxima of cloud fraction agree well with those of water vapor, clear-sky cooling rates, and diabatic convergence at 200 hPa. The use of direct CTT measurements suggests the CTT in specific Pacific basins exhibit different characteristics as the frequency distribution of the tropical SST varies from boreal winter to summer. When averaging over the tropics as a whole, the CTT distributions are approximately unchanged primarily because of cancellation by the variations associated with individual regions. An analysis of the response of the tropical mean CTT anomaly time series to the SST indicates that a possible negative relationship is present, whereas the relationship tends to be positive over the tropical western Pacific and Indian Oceans. In addition, it is suggested to interpret the FAT hypothesis, and the more recent proportionately higher anvil temperature (PHAT) hypothesis, by using the temperature at the maximum cloud detrainment level instead of the CTT.

Equatorial Planetary Waves and Their Signature in Atmospheric Variability

Abstract Equatorial planetary waves are a fundamental component of the tropical climate system. Previous studies have examined their structure in the climatological-mean circulation, their role in the climatological-mean momentum balance of the tropics, and their contribution to the climatological-mean upwelling across the tropical tropopause. In this study, the authors focus on the contribution of the equatorial planetary waves to variability in the tropical circulation about its climatological-mean state. The equatorial planetary waves that dominate the climatological mean exhibit considerable variability on intraseasonal and interannual time scales. Variability in the amplitude of the equatorial planetary waves is associated with a distinct pattern of equatorially symmetric climate variability that also emerges from empirical orthogonal function analysis of various tropical dynamical fields. Variability in the equatorial planetary waves is characterized by variations in 1) convection in the deep tropics, 2) eddy momentum flux convergence and zonal-mean zonal wind in the tropical upper troposphere, 3) the mean meridional circulation of the tropical and subtropical troposphere, 4) temperatures in the tropical lower stratosphere and subtropical troposphere of both hemispheres, and 5) the amplitude of the upper tropospheric anticyclones over the western tropical Pacific Ocean. It is argued that pulsation of the equatorial planetary waves provides an alternative framework for interpreting the response of the tropical circulation to a range of climate phenomena. Pulsation of the equatorial planetary waves is apparent in association with opposing phases of El Niño–Southern Oscillation and select phases of the Madden–Julian oscillation. Pulsation of the equatorial planetary waves also contributes to variability in measures of the width of the tropical belt.

Intensifying Pacific trade winds drive regional sea level trends

Sea level in the western tropical Pacific Ocean has been increasing at a rate about 3 times the global average rate of sea level rise, as observed from satellite altimetry and tide gauges. Why are sea level trends so much different in this region? Previous studies have suggested that the high rate of sea level change in the western tropical Pacific is associated with the natural variation of the El Niño–Southern Oscillation. However, using a general circulation model, Merrifield and Maltrud show that western tropical Pacific sea level trends are likely due to a gradual intensification of the Pacific trade winds in the past 2 decades. They also highlight other aspects of ocean circulation that have been altered in response to the intensifying trade winds. Some previous research has suggested that the trade wind intensification is a result of global warming, although that has yet to be verified. If that is the case, the authors conclude, the western tropical Pacific sea level trends will likely continue to be anomalously high. (Geophysical Research Letters, doi:10.1029/2011GL049576, 2011)

Two new species of Photonectes (Teleostei: Stomiidae) from the Indo-Pacific, and a re-examination of P. Achirus

Flynn, A. J.and Klepadlo, C. 2012. Two new species of Photonectes (Teleostei: Stomiidae) from the Indo-Pacific, and a re-examination of P. achirus. Memoirs of Museum Victoria 69: 259–267. Two new species of the mesopelagic fish genus Photonectes (family Stomiidae) from the Indo-Pacific are described. Both are referred to the subgenus Photonectes because they lack pectoral fins, have no fleshy tissue on their dorsaland anal-fin rays, have a pelvic-fin insertion closer to the caudal-fin base than the snout, and have IP photophores located on the isthmus at a position midway along the mandible, posterior to the mandibular symphysis. Photonectes waitti sp. nov., known from the tropical western and central Pacific Ocean, northwestern Coral Sea and north Indian Ocean, is most similar to P. coffea, differing from it by the number of PV photophores (24—25 vs. 29—31), gill filaments reduced (vs. greatly elongate), jaw teeth long and short canines (vs. short canines only), and barbel length less than (vs. equal to or greater than) head length. Photonectes paxtoni sp. nov., known from the tropical western Pacific Ocean, off Papua New Guinea, has a short barbel, less than head length, ending in a very large bulb without any terminal filaments or appendages, and different photophore numbers compared to other members of the subgenus: VAV 15—16 (vs. 10—15), AC 13 (vs. 9—12), and IV 29 (vs. 30—46). Photonectes achirus is re-examined with respect to previously unreported dark pigment on the head.