Remote North Pacific Research Articles

Variability in the Concentration of Lithium in the Indo‐Pacific Ocean

AbstractLithium has limited biological activity and can readily replace aluminium, magnesium and iron ions in aluminosilicates, making it a proxy for the inorganic silicate cycle and its potential link to the carbon cycle. Data from the North Pacific Ocean, tropical Indian Ocean, Southern Ocean and Red Sea suggest that salinity normalized dissolved lithium concentrations vary by up to 2%–3% in the Indo‐Pacific Ocean. The highest lithium concentrations were measured in surface waters of remote North Pacific and Indian Ocean stations that receive relatively high fluxes of dust. The lowest dissolved lithium concentrations were measured just below the surface mixed layer of the stations with highest surface water concentrations, consistent with removal into freshly forming aluminium rich phases and manganese oxides. In the North Pacific, water from depths >2,000 m is slightly depleted in lithium compared to the initial composition of Antarctic Bottom Water, likely due to uptake of lithium by authigenically forming aluminosilicates. The results of this study suggest that the residence time of lithium in the ocean may be significantly shorter than calculated from riverine and hydrothermal fluxes.

Relative abundance of derelict fishing gear in the Hawaii-based pelagic longline fishery grounds as estimated from fishery observer data

Derelict fishing gear (DFG) is abundant across the remote North Pacific Ocean, accumulating in convergence zones that coincide with the fishing grounds of the Hawai’i-based pelagic longline fishery. Longlines are prone to snagging DFG, providing an opportunistic, yet regular, reporting mechanism by longline fishery observers (fishery-dependent data). We apply a zero-inflated negative binomial model previously used to standardize catch per unit effort (CPUE) for bycatch and incidentally caught species in this fishery to estimate DFG relative abundance and qualitative trends within the longline fishing grounds. During 2008–2016, observers reported 1326 marine debris items intercepted by longlines, dominated by DFG at nearly 90%. Modeling results suggest that the relative abundance of DFG has declined ~66% from 2008–2016. DFG standardized CPUE was higher for longlines fished inside the North Pacific Subtropical Convergence Zone (versus outside) and increased moving eastward and northward toward the Great Pacific Garbage Patch. Despite substantially less effort in the shallow-set sector of the fishery (∼60 m depth), DFG standardized CPUE was four-fold greater than that of the deep-set sector (∼250 m) suggesting that marine debris observer reporting focused in this sector may be most effective. Some fishermen voluntarily stow snagged debris; incentivizing at-sea removal may elicit further cooperation.

Frequency based satellite monitoring of small scale explosive activity at remote North Pacific volcanoes

Monitoring of volcanoes in the North Pacific can be an expensive and sometimes dangerous task, specifically for those located in Alaska (USA) and Kamchatka (Russia). An active frequency detection method previously used at Stromboli, Italy, uses the thermal- and mid-infrared wavelength bands from the Moderate Resolution Imaging Spectroradiometer (MODIS) satellite data to detect anomalies at a volcano. This method focuses on small scale explosive activity, often referred to as Strombolian activity which can produce small spatter fields near a volcano's active vent. In the North Pacific, there are a number of volcanoes which exhibit small scale explosive activity and three are the focus of this study: Chuginadak (Mt. Cleveland) and Shishaldin in Alaska, and Karymsky Volcano in Kamchatka. Satellite images from the Advanced Very High Resolution Radiometer (AVHRR) were used to monitor the frequency of thermal features as well as the occurrence of ash plumes at each volcano. This data was then used to produce a time series spanning 2005–2010 for all three volcanoes. During this time period, each volcano underwent a series of eruptive cycles including background levels of activity, heightened frequency of small explosions (identified as precursory activity), and heightened activity typified by ash plume-producing eruptions. Each location has a unique precursory signal, both in timing and magnitude. The use of a previously developed method on a new sample set of volcanoes has proved the validity of this method as a monitoring tool for volcanoes with small scale explosive activity. This method should be applied to a larger set of volcanoes to continue the development and database production for its use as a volcano monitoring tool.

On the export of reactive nitrogen from Asia: NO<sub>x</sub> partitioning and effects on ozone

Abstract. The partitioning of reactive nitrogen (NOy was measured over the remote North Pacific during spring 2006. Aircraft observations of NO, NO2, total peroxy nitrates (ΣPNs), total alkyl and multi-functional nitrates (ΣANs) and nitric acid (HNO3, made between 25° and 55° N, confirm a controlling role for peroxyacyl nitrates in NOx production in aged Asian outflow. ΣPNs account for more than 60% of NOy above 5 km, while thermal dissociation limits their contribution to less than 10% in the lower troposphere. Using simultaneous observations of NOx, ΣPNs, ΣANs, HNO3 and average wind speed, we calculate the flux of reactive nitrogen through the meridional plane of 150° W (between 20° and 55° N) to be 0.007 ± 0.002 Tg N day−1, which provides an upper limit of 23 ± 6.5% on the transport efficiency of NOy from East Asia. Observations of NOx, and HOx are used to constrain a 0-D photochemical box model for the calculation of net photochemical ozone production or tendency (Δ O3) as a function of aircraft altitude and NOx concentrations. The model analysis indicates that the photochemical environment of the lower troposphere (altitude < 6 km) over the north Pacific is one of net O3 destruction, with an experimentally determined crossover point between net O3 destruction and net O3 production of 60 pptv NOx. Qualitative indicators of integrated net O3 production derived from simultaneous measurements of O3 and light alkanes (Parrish et al., 1992), also indicate that the north Pacific is, on average, a region of net O3 destruction.

Legacy and contemporary persistent organic pollutants in North Pacific albatross

Here we report the first measurements of polybrominated diphenyl ethers (PBDE 47, 99, and 153) alongside 11 organochlorine pesticides (OCPs) and 28 polychlorinated biphenyls (PCBs) in the plasma of albatross from breeding colonies distributed across a large spatial east-west gradient in the North Pacific Ocean. North Pacific albatross are wide-ranging, top-level consumers that forage in pelagic regions of the North Pacific Ocean, making them an ideal sentinel species for detection and distribution of marine contaminants. Our work on contaminant burdens in albatross tissue provides information on transport of persistent organic pollutants (POPs) to the remote North Pacific and serves as a proxy for regional environmental quality. We sampled black-footed (Phoebastria nigripes; n = 20) and Laysan albatross (P. immutabilis; n = 19) nesting on Tern Island, Hawaii, USA, and Laysan albatross (n = 16) nesting on Guadalupe Island, Mexico. Our results indicate that North Pacific albatross are highly exposed to both PCBs and OCPs, with levels ranging from 8.8 to 86.9 ng/ml wet weight and 7.4 to 162.3 ng/ml wet weight, respectively. A strong significant gradient exists between Laysan albatross breeding in the Eastern Pacific, having approximately 1.5-fold and 2.5-fold higher levels for PCBs and OCPs, respectively, compared to those from the Central Pacific. Interspecies levels of contaminants within the same breeding site also showed high variation, with Tern black-footed albatross having approximately threefold higher levels of both PCBs and OCPs than Tern Laysan albatross. Surprisingly, while PBDEs are known to travel long distances and bioaccumulate in wildlife of high trophic status, we detected these three PBDE congeners only at trace levels ranging from not detectable (ND) to 0.74 ng/ml wet weight in these albatross.

Aeolian Contamination of Se and Ag in the North Pacific from Asian Fossil Fuel Combustion

Energy production from fossil fuels, and in particular the burning of coal in China, creates atmospheric contamination that is transported across the remote North Pacific with prevailing westerly winds. In recent years this pollution from within Asia has increased dramatically, as a consequence of vigorous economic growth and corresponding energy consumption. During the fourth Intergovernmental Oceanographic Commission baseline contaminant survey in the western Pacific Ocean from May to June, 2002, surface waters and aerosol samples were measured to investigate whether atmospheric deposition of trace elements to the surface North Pacific was altering trace element biogeochemical cycling. Results show a presumably anthropogenic enrichment of Ag and of Se, which is a known tracer of coal combustion, in the North Pacific atmosphere and surface waters. Additionally, a strong correlation was seen between dissolved Ag and Se concentrations in surface waters. This suggests that Ag should now also be considered a geochemical tracer for coal combustion, and provides further evidence that Ag exhibits a disturbed biogeochemical cycle as the result of atmospheric deposition to the North Pacific.

Geographical distribution of particle number density in the accumulation mode range over the North Pacific Ocean

From 1998 to 2002, seven research cruises were conducted over the widespread areas of the North Pacific Ocean to investigate particle number densities in the accumulation mode range with the diameter of 0.1–2.5 µm. The densities over the Bering Sea, and the northeastern and southwestern North Pacific Ocean showed median values of 69.1, 122.8, and 66.9 cm − 3 , respectively, in the summer. These measurements would be representatives of a background marine atmosphere over the remote North Pacific Ocean. Asian outflows bring the particles to the northwestern area of the North Pacific Ocean, especially to the coastal seas close to the land, in the transitional seasons of spring and autumn. Even in the summer, the influences of the outflows on the densities over the northwestern area of the North Pacific Ocean were found, although a high marine productivity would also contribute to an increase in the densities. Transport of combustion-derived particles from the land is a critical factor controlling the densities in the continentally modified atmosphere with a short transport time of the air masses from the land. In the background marine atmosphere, on the other hand, secondary production processes over the ocean would be a main factor for the densities due to the reduced influence of continental-derived particles.

Free amino acids in marine aerosols over the western North Pacific Ocean

Abstract Atmospheric input of fixed nitrogen species to the ocean has attracted considerable attention from the viewpoint of the oceanic biogeochemical cycle of nitrogen, although few measurements of organic nitrogen compounds in atmospheric aerosols have been extensively conducted over remote ocean areas. In this study, we report the geographical distribution of dissolved free amino acids (DFAA) in the water-soluble fraction of two size-segregated marine aerosols over the western North Pacific. The concentrations of DFAA showed higher values over the region north of 30°N, whereas they clearly decreased south of 30°N. Approximately 59–96% of DFAA was found in fine-mode particles. Long-range transport from continental sources could largely contribute to DFAA in marine aerosols over the remote North Pacific.

Surface temperature control in the North and tropical Pacific during the last glacial maximum

Based on coupled modelling evidence we argue that topographically-induced modifications of the large-scale atmospheric circulation during the last glacial maximum may have led to a reduction of the westerlies, and a slowdown of the Pacific subtropical gyre as well as to an intensification of the Pacific subtropical cell. These oceanic circulation changes generate an eastern North Pacific warming, an associated cooling in the Kuroshio area, as well as a cooling of the tropical oceans, respectively. The tropical cooling pattern resembles a permanent La Nina state which in turn forces atmospheric teleconnection patterns that lead to an enhancement of the subtropical warming by reduced latent and sensible cooling of the ocean. In addition, the radiative cooling due to atmospheric CO2 and water vapor reductions imposes a cooling tendency in the tropics and subtropics, thereby intensifying the permanent La Nina conditions. The remote North Pacific response results in a warming tendency of the eastern North Pacific which may level off the effect of the local radiative cooling. Hence, a delicate balance between oceanic circulation changes, remotely induced atmospheric flux anomalies as well local radiative cooling is established which controls the tropical and North Pacific temperature anomalies during the last glacial maximum. Furthermore, we discuss how the aftermath of a Heinrich event may have affected glacial temperatures in the Pacific Ocean.

PCDDs, PCDFs, and coplanar PCBs in albatross from the North Pacific and Southern Oceans: levels, patterns, and toxicological implications.

Concentrations of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and coplanar polychlorinated biphenyls (coplanar PCBs) were determined in five albatross species collected from the North Pacific and Southern Oceans to assess the north-south differences in residue levels, accumulation patterns, and toxic potential. Black-footed and Laysan albatrosses from the North Pacific Ocean contained higher levels of PCDD/Fs and coplanar PCBs than albatrosses from the Southern Ocean, indicating that emission sources of these contaminants were predominant in the northern hemisphere. Residue levels in albatrosses from the remote North Pacific Ocean far from the point source of pollution were comparable to or higher than those in terrestrial and coastal birds from contaminated areas in developed nations, suggesting the specific exposure and accumulation of PCDD/Fs and coplanar PCBs in albatross. The long life span and ingestion of plastic resin pellets by albatrosses could be the plausible explanations for the elevated accumulation of persistent and lipophilic contaminants including PCDD/Fs and coplanar PCBs in these birds. Relative proportions of PCDFs and coplanar PCBs in albatross were higher than those observed in birds inhabiting terrestrial and coastal areas, suggesting that these toxic chemicals may have higher transportability by air and water than PCDDs. Congener patterns of PCDD/Fs in albatross showed less variability as compared to those in terrestrial species, indicating that contamination patterns of PCDD/Fs were similar within the open ocean environment. Contributions of PCDD/Fs to total TEQs in albatrosses from the open ocean were generally lower than those in terrestrial birds, suggesting different toxic potency of PCDD/Fs and coplanar PCBs on animals inhabiting open ocean and terrestrial environment. Whereas albatrosses from southern oceans retained lower TEQ concentrations, possible adverse effects of PCDD/Fs and coplanar PCBs to black-footed and Laysan albatrosses of the North Pacific Ocean may be suspected from TEQ levels.

Spatial and temporal characteristics of dust storms in China and its surrounding regions, 1960–1999: Relations to source area and climate

Compilation and analysis of the past 40 years of dust storm reports from China allow estimation of the meteorological conditions of dust storms, dust transport routes, and eolian source regions. Our results indicate that dust storms in China are highly associated with the frontal systems and the Mongolian cyclonic depression. The spatial distribution of dust storms indicates that there are two dominant source regions of eolian dust raised from China and its surrounding regions. The major source is the gobi deserts in Mongolia and northern China. Another source region is the Taklimakan Desert in western China. However, dust entrained from the two sources makes different contributions to downwind deposition regions. In most cases, dust materials entrained from the gobi deserts of Mongolia and China can only be entrained to an elevation of <3000 m. They are the dominant source materials of the eolian sediments in the Loess Plateau, southeastern China, offshore regions, and the near North Pacific Ocean. Dust materials from the Taklimakan Desert can be entrained to an elevation of >5000 m and then transported over long distances (∼5000 km) by the westerlies. These materials are not the main sources of the dust deposited in the proximal region, such as the Chinese Loess Plateau, but they are important sources of the eolian fraction of pelagic sediment in the remote North Pacific Ocean.

Impact of Asian emissions on the remote North Pacific atmosphere: Interpretation of CO data from Shemya, Guam, Midway and Mauna Loa

In this study we look at the concentration of CO at four remote stations in the North Pacific to evaluate the impact of Asian industrial emissions on the remote atmosphere. Using a locally weighted smoothing technique to identify individual data outliers from the seasonal cycle, we have identified 22–92 outliers or “events” (greater than 5 ppbv above the seasonal cycle) at each site for the 3–6 year data records. Using isentropic back trajectories, we identify a possible source region for each event and present a distribution of the trajectory types. For the events at Midway, Mauna Loa, Guam, and Shemya, we are able to identify a source region for the elevated CO in 82, 72, 65, and 50% of the events, respectively. At Mauna Loa and Midway a majority of the events occur during spring and are usually associated with transport from Asia. These events bring the highest CO mixing ratios observed at any time during the year to these sites, with CO enhancements up to 46 ppb. At Guam, easterly trade winds are the norm, but occasionally synoptic events bring Asian emissions to the island, generally during late summer and fall, from either East Asia or Southeast Asia (e.g., Indonesia). These events bring with them the largest CO enhancements of any of the four sites considered in this paper, up to 58 ppb. Finally, to examine the robustness of our conclusions, we redo our analysis using the more stringent definition that an event must be either 10 or 15 ppb above the seasonal cycle. Although this reduces the number of events identified at each site, it does not significantly change the fraction of events which can be attributed to a known source.

Atmospheric non‐sea‐salt sulfate, nitrate and methanesulfonate over the China Sea

To characterize atmospheric particulate non‐sea‐salt (nss) sulfate, nitrate, methanesulfonate (MSA), and selected trace elements over the China Sea, aerosol sampling was conducted at Qingdao and Xiamen, which are on the coast of China, and over offshore regions of the East China Sea. The atmospheric concentrations of nss sulfate and nitrate were much higher along the coast of the China Sea than over remote oceans, with mean values of 10 to 12 μg m−3 for nss sulfate and 5.6 to 7.7 μg m−3 for nitrate. The mean concentrations of atmospheric MSA ranged from 0.029 to 0.066 μg m−3 over the China Sea; these are comparable to values from other coastal sites and remote oceans. Both MSA and nss sulfate are concentrated in particles ≤0.5 μm in diameter, while nitrate shows a bimodel distribution. There was no clear correlation between nss sulfate and MSA concentrations, with the ratios of nss sulfate to MSA (60–870) being substantially higher than those over remote oceans. Based on a biogenic nss‐sulfate/MSA ratio of 18 obtained from the remote North Pacific, the estimated anthropogenic sulfate accounts for 81–97% of the total nss sulfate over the China Sea. Results of factor analyses suggest that coal combustion is the dominate source for anthropogenic sulfate over the basin of the China Sea. Oil combustion appears to be an additional important contributor for anthropogenic sulfate in the region of the East China Sea, but this feature does not exist in the South China Sea region. Pyrometallurgical nonferrous metal smelting is among the additional sources for nss sulfate in this region.

Measurements of nitric acid and aerosol nitrate at the Mauna Loa Observatory during the Mauna Loa Observatory Photochemistry Experiment 1988

Ambient air concentrations of nitric acid vapor and aerosol nitrate were measured above the remote North Pacific between May 1 and June 5, 1988, during the Mauna Loa Observatory Photochemistry Experiment (MLOPEX). Nighttime (free tropospheric) mean values were 30 pptv nitrate aerosol and 103 pptv nitric acid. Daytime values, representative of island‐modified marine boundary layer air, averaged 60 pptv aerosol and 130 pptv nitric acid. The measurements were generally consistent with previous measurements in the remote North Pacific including free tropospheric measurements of nitric acid during NASA's Global Tropospheric Experiment/Chemical Instrumentation Test and Evaluation (GTE/CITE 2). MLOPEX observations are smaller than model HNO3/NOx ratios. However, the magnitude of this discrepancy is obscured by uncertainties, mainly in the model OH concentration and nitric acid photolysis rates. Nonetheless, large observed variations in the HNO3/NOx ratio likely indicate significant loss of nitric acid, at least part of the time, by some process in addition to vapor phase photolysis and destruction by OH. Several processes are considered, but no firm conclusion is reached.

Relationships between the dust concentrations over eastern Asia and the remote North Pacific

Dust storm reports as well as chemical data indicate that 1988 and 1989 were high‐dust and low‐dust years in eastern Asia, respectively. This pattern was not reflected in data from Midway, a remote island in the North Pacific, where the mineral aerosol concentrations during 1989 were as high as or higher than any year for which data are available. Analyses of meteorological data showed that the amount of precipitation, the strength of the westerly winds, and the position of large‐scale meteorological features were related to the dust concentrations over eastern Asia. The observed disparity in the interannual trend in dust concentrations over Beijing and Midway was explained by differences in the source regions for the dust. Dust over eastern Asia evidently originates from source regions to the northeast of the Tibetan Plateau, while dust at Midway is ascribed to dust materials transported from the desert lands in western China. The Asian dust flux to the open ocean is influenced not only by conditions in or near the source regions but also by the large‐scale atmospheric circulation patterns.

Estimates of the transport of trace metals from the ocean to the atmosphere

The Bubble Interfacial Microlayer Sampler (BIMS) was used in the North Atlantic to determine the enrichment factors, relative to sodium and the ocean (EFsea), for a series of trace metals on bubble‐derived atmospheric sea salt particles. No enrichment was found for K and Mg within the analytical precision of ±10%. Mean EFsea values determined for Al, Co, Cu, Fe, Mn, Pb, V, and Zn ranged from 10 to 20,000. Positive correlations were found between bubble generation depth and the EFsea values for Fe, Pb, Sc, and Zn. Estimates suggest that the ocean is the primary global source of atmospheric K and Mg, that it is potentially a nontrivial (5–20% of the total) source of atmospheric Cu, V, and possibly Zn, and that it is an insignificant source of Al, Co, Fe, Mn, Pb, and Sc. In the remote North Pacific, during certain periods of the year, the ocean may be the primary source for all these elements present on aerosol particles with diameters greater than ∼3 μm.