colored dissolved organic matter dynamics across the shelf basin interface in the western arctic ocean 1 spatial variations in the concentration and nature of colored dissolved organic matter cdom in the western arctic ocean were examined by three dimensional excitation emission matrix 3 d eem spectroscopy cdom profiles showed distinctive features well correlated with hydrographic characteristics cdom fluorescence was particularly high at depths between 40 and 200 m up to 3 fluorescence units fl u in both chukchi sea and beaufort sea transects penetration of the high cdom signal formed on the shelves into the canada basin was confined to the upper halocline layer salinity of 33 1 this layer had distinctive 3 d eem fingerprints in fluorescence spectra showing a marked terrestrial humic signature the presence of cdom in the halocline layer likely resulted from two main processes the brine rejection during sea ice formation and transport across the sediment water interface during early diagenesis despite the high primary productivity in the chukchi shelf cdom contribution from in situ production seemed to have little influence on the overall cdom distributions in the study area

comparative vertical distributions of iron in the japan sea the bering sea and the western north pacific ocean 1 the vertical distributions of dissolvable unfiltered fe concentrations in semi closed oceanic regions such as the japan sea and the bering sea are characterized by a gradual increase with depth in the intermediate and deep waters however there is a rapid decrease in the dissolvable fe concentration over the narrow depth range between deep and bottom waters with constantly lower concentrations observed in the bottom waters of the japan sea japan basin probably from the injection of newly formed bottom water in addition the rapid increase in dissolvable fe concentrations in bottom waters in the western north pacific ocean may be due to the resuspension of sediments from the seafloor or the slope however there are no differences of labile dissolved filtered fe concentrations and fe iii hydroxide solubility between deep and bottom waters revealing that dissolved fe concentrations in deep waters may be controlled primarily by fe iii complexation with natural organic ligands dissolved fe concentrations humic type fluorescence intensity and fe iii solubility correlate well with po4 with different slopes between intermediate and deep waters in the north pacific ocean however there is no different depth regime between them in semi closed oceanic regions the most statistically significant correlation between the fe iii solubility and fluorescence intensity was found with a nearly linear relation in intermediate and deep waters at all stations of the semi closed and open oceanic regions this result suggests that the distributions of humic type fluorescent organic matter may be responsible for fe iii solubility and dissolved fe concentrations in deep oceanic waters

halocline structure in the canada basin of the arctic ocean 1 we examine the varieties and spatial distributions of pacific and eastern arctic origin halocline waters in the canada basin using 2002 2003 hydrographic data the halocline structure in the canada basin is different from the eastern arctic halocline because it includes fresher pacific winter waters that form a cold halostad which lies above the eastern arctic origin lower halocline waters the structure of the halostad in the canada basin however is not spatially uniform and depends on the pathway and history of the source water pacific winter water entering through the bering strait becomes salty due to sea ice formation and this in turn is dependent on the occurrence and distribution of polynyas in particular saline water from the eastern chukchi sea forms thick halostad and causes depression of the isohalines in the southern canada basin this depression influences thermohaline structure of the oceanic beaufort gyre

iron and humic type fluorescent dissolved organic matter in the chukchi sea and canada basin of the western arctic ocean 1 the concentrations of dissolved fe d fe total dissolvable fe t fe humic type fluorescence intensity humic f intensity as humic type fluorescent dissolved organic matter and nutrients were vertically determined in the shelf slope and basin regions chukchi sea and canada basin of the western arctic ocean during 1 27 september 2008 in all stations the remarkably high d fe and humic f intensity were found at depths between 25 and 200 m with the subsurface maxima of d fe 1 0 3 2 nm and humic f intensity 4 5 quinine sulfate units in the upper halocline layer upper hl being associated with a prominent nutrient maximum the high d fe and humic f intensity within the upper hl are probably attributed to the fe iii complexation with natural organic ligands such as marine dissolved humic substances resulting from main processes of the brine rejection during sea ice formation and interactions with sediments on the shelves however subsurface maxima 10 50 nm of t fe were found in the lower halocline layer beneath the upper hl of all slope and basin regions and are mainly attributed to the resuspension of sedimentary particles in the shelf region the finding of subsurface iron maxima in the halocline water of all regions may be the first confirmation for the lateral iron transport into the halocline layer from the shelves to the arctic basin

mercury radar imaging evidence for polar ice the first unambiguous full disk radar mapping of mercury at 3 5 centimeter wavelength with the goldstone 70 meter antenna transmitting and 26 antennas of the very large array receiving has provided evidence for the presence of polar ice the radar experiments conducted on 8 and 23 august 1991 were designed to image the half of mercury not photographed by mariner 10 the orbital geometry allowed viewing beyond the north pole of mercury a highly reflective region was clearly visible on the north pole during both experiments this polar region has areas in which the circular polarization ratio pt was 1 0 to 1 4 values 0 1 are typical for terrestrial planets such high values of have hitherto been observed in radar observations only from icy regions of mars and icy outer planet satellites

mars radar mapping strong backscatter from the elysium basin and outflow channel abstract radar reflectivity maps of mars obtained at arecibo in 1990 using a modified delay doppler technique have revealed strong depolarized echoes coming from the elysium flood basin and outflow channel as well as from elysium mons this result is consistent with recent studies which show that much of the basin channel floor is covered with lava flows

importance of organic fe complexing ligands in the mississippi river plume abstract as part of a larger program focused on understanding the biogeochemistry of large river plumes we participated in two expeditions during 2000 to sample the mississippi river plume surface water samples were collected using a trace metal clean towed fish and analyzed for total dissolved fe organic fe complexing ligands and their associated conditional stability constants the ligands in the river plume have conditional stability constants log k fel between 10 5 and 12 3 with an average of 11 2 and standard deviation of 0 6 very similar to ligands found in the open ocean comparison of high flow and low flow regimes indicates that variability in flow may be the main cause of the variability in fe concentrations in the plume the organic fe complexing ligands are in greatest excess during a time of higher flow these ligands are responsible for maintaining very high 5 nm fe concentrations throughout the plume due to complexation with these organic ligands the concentration of fe remains above the fe hydroxide solubility level until a salinity above 35 is reached where there appears to be a sink for fe in the less productive waters therefore fe is transported a great distance from the river source and is available for biological utilization in the coastal zone

carbon export and cycling by the yukon tanana and porcupine rivers alaska 2001 2005 1 loads and yields of dissolved and particulate organic and inorganic carbon doc poc dic pic were measured and modeled at three locations on the yukon river yr and on the tanana and porcupine rivers tr pr in alaska during 2001 2005 total yr carbon export averaged 7 8 tg c yr 1 30 as oc and 70 as ic total c yields 0 39 1 03 mol c m 2 yr 1 were proportional to water yields 139 356 mm yr 1 r2 0 84 at all locations summer doc had an aged component fraction modern fm 0 94 0 97 except in the permafrost wetland dominated pr where doc was modern poc had fm 0 63 0 70 doc had high concentration high aromaticity and high hydrophobic content in spring and low concentration low aromaticity and high hydrophilic content in winter about half of annual doc export occurred during spring dic concentration and isotopic composition were strongly affected by dissolution of suspended carbonates in glacial meltwater during summer

northern latitude chemical weathering rates clues from the mackenzie river basin canada abstract the main scope of this study is to investigate parameters controlling chemical weathering rates for a large river system submitted to subarctic climate more than 110 river water samples from the mackenzie river system northern canada have been sampled and analyzed for major and trace elements and sr isotopic ratios in the dissolved phase the three main morphological units are reflected in water chemistry rivers from the canadian shield are very dilute dominated by silicate weathering millot et al 2002 whereas the rivers of the rocky and mackenzie mountains as well as the rivers of the sedimentary interior platform are dominated by carbonate weathering and are so 4 rich compared to the rivers of the mackenzie and rocky mountains the rivers of the interior plains are organic silica and na rich and constitute the dominant input term to the mackenzie river mainstream rivers of the canadian shield area do not significantly contribute to the mackenzie river system using elemental ratios and sr isotopic ratios a mathematical inversion procedure is presented that distinguishes between solutes derived from silicate weathering and solutes derived from carbonate weathering carbonate weathering rates are mostly controlled by runoff which is higher in the mountainous part of the mackenzie basin these rates are comparable to the carbonate weathering rates of warmer areas of the world it is possible that part of the carbonate weathering is controlled by sulfide oxidative weathering but its extent remains difficult to assess conversely to what was stated by edmond and huh 1997 overall silicate weathering rates in the mackenzie basin are low ranging from 0 13 to 4 3 tons km 2 yr na k ca mg and confirm the negative action of temperature on silicate weathering rates for river basins in cold climates in contrast to what has been observed in other large river systems such as the amazon and ganges rivers silicate weathering rates appear 3 to 4 times more elevated in the plains than in the mountainous headwaters this contradicts the raymo hypothesis raymo and ruddiman 1992 isotopic characterization of suspended material clearly shows that the higher weathering rates reported for the plains are not due to the weathering of fine sediments produced in the mountains e g by glaciers and deposited in the plains rather the relatively high chemical denudation rates in the plains are attributed to lithology uncompacted shales high mechanical denudation and the abundance of soil organic matter derived from incomplete degradation and promoting crystal lattice degradation by element complexation the three to fourfold factor of chemical weathering enhancement between the plains and mountains is similar to the fourfold factor of enhancement found by moulton et al 2000 between unvegetated and vegetated watershed this study confirms the negative action of temperature on silicate weathering for cold climate but shows that additional factors such as organic matter associated with northern watersheds are able to counteract the effect of temperature this acceleration by a factor of 4 in the plains is equivalent to a 6 c increase in temperature

craters hosting radar bright deposits in mercury s north polar region areas of persistent shadow determined from messenger images 1 radar bright features near mercury s poles were discovered in earth based radar images and proposed to be water ice present in permanently shadowed areas images from messenger s one year primary orbital mission provide the first nearly complete view of mercury s north polar region as well as multiple images of the surface under a range of illumination conditions we find that radar bright features near mercury s north pole are associated with locations persistently shadowed in messenger images within 10 of the pole almost all craters larger than 10 km in diameter host radar bright deposits there are several craters located near mercury s north pole with sufficiently large diameters to enable long lived water ice to be thermally stable at the surface within regions of permanent shadow craters located farther south also host radar bright deposits and show a preference for cold pole longitudes thermal models suggest that a thin insulating layer is required to cover these deposits if the radar bright material consists predominantly of long lived water ice many small 10 km diameter and low latitude extending southward to 66 n craters host radar bright material and water ice may not be thermally stable in these craters for 1 gy even beneath an insulating layer the correlation of radar bright features with persistently shadowed areas is consistent with the deposits being composed of water ice and future thermal modeling of small and low latitude craters has the potential to further constrain the nature source and timing of emplacement of the radar bright material

water column iron dynamics in the subarctic north pacific ocean and the bering sea 1 we measured water column iron concentrations from west to east along 47 n in the subarctic north pacific and in the bering sea in the north pacific dissolved fe d fe showed surface depletion mid depth maxima at 1000 1500 m west 1 3 1 6 nm east 0 9 1 1 nm and a gradual decrease with depth below 3500 4000 m depth west 1 1 1 4 nm east 0 6 0 7 nm d fe and total soluble fe t fe in deep water showed a decreasing trend eastward the higher iron concentrations in western deep waters probably result from higher inputs of dissolved fe through atmospheric deposition or lateral transport in contrast d fe throughout the bering sea showed a consistent depth regime characterized by a rapid increase with depth to mid depths a gradual increase with depth in intermediate water to a maximum of 1 6 1 7 nm at 1500 2250 m and a gradual decrease with depth to 1 3 1 4 nm at 3700 m higher iron concentrations and deeper d fe maxima in the bering sea are likely due to higher biological productivity and greater and deeper d fe input from the decomposition of sinking particulate organic matter in deep water we suggest that the higher concentrations and deeper input of d fe as well as po4 and humic type fluorescent dissolved organic matter in the bering sea probably results from the longer time for the accumulation of decomposition products resulting from iron supply from the organic rich downslope sediment along the steep continental slopes and slow replacement of the deep water in the bering sea basin

iron in the japan sea and its implications for the physical processes in deep water 1 labile dissolved fe dfe 0 22 m fraction and total dissolvable fe tdfe unfiltered were examined throughout the water column of the northeastern japan basin and mid eastern yamato basin basin regions in the japan sea we observed extremely high vertically integrated tdfe inventories and low nutrient concentrations at the surface water in both basins probably resulting from high atmospheric fe input to nutrient depleted surface water dfe in both basins was characterized by mid depth maxima and below that a slight decrease with depth in deep water and uniform concentration in bottom water in the japan basin surprisingly tdfe concentrations in bottom water were lower than those in deep water resulting from the injection of new bottom water on the contrary tdfe concentrations in bottom water of the yamato basin increased gradually with depth and were higher than those in deep water probably due to the supply of iron during the horizontal transport of the bottom water in the japan basin towards the yamato basin the tdfe with a high percentage of labile particulate fe tdfe minus dfe may have important implications for understanding the physical processes of bottom water in the japan sea

radar altimetry of mercury a preliminary analysis measurements of mercurian topography based on arecibo radar observations are presented the data which were obtained from 1978 to 1984 cover much of the equatorial zone of mercury between 12on and 5os latitude over thirty continuous altitude profiles were obtained each spanning from 20 to 90 degrees of longitude at a resolution of 0 15 o longitude by 2 5 o latitude radar depths for large craters support previous indications from imagery that mercurian craters are shallower than lunar craters of the same size one very large 800 km impact basin shows some distinct topographic structure although its relative shallowness suggests postimpact modification by isostatic relaxation or volcanic filling the plains of tir planitia appear topographically smooth to the radar these plains extend well into the hemisphere not imaged by mariner 10 possibly forming part of a large annulus of smooth plains around caloris basin the circum caloris smooth plains are strongly down bowed indicating subsidence under a load this and other similarities to lunar maria suggest a volcanic origin for these plains additional areas of topographically smooth terrain have been found in both the imaged and unimaged hemispheres several ridges scarps and fault zones have been identified in the altimetry three mapped arcuate scarps show heights of about 700 m and cross sectional widths of about 70 km one of these features is clearly a ridge while the other two scarps have a more ridge like appearance than is suggested by images one large scale topographic drop of 3 km correlates well with a mapped system of faults and intracrater scarps the equatorial zone of mercury shows 7 km of maximum relief although the typical elevation difference between highlands and lowlands is closer to 3 km three major highland areas are found the largest two of which are roughly antipodal and aligned within about 10 o of the hot poles of mercury the unimaged hemisphere possessing both large craters and topographically smooth areas does not appear to be markedly different in its topography from the imaged hemisphere no evidence has been found for another caloris type impact structure in the unimaged hemisphere

the plume of the yukon river in relation to the oceanography of the bering sea abstract physical and biological oceanography of the northern bering sea including the plume of the yukon river were studied using satellite data in conjunction with shipboard measurements the satellite data recorded by the noaa very high resolution radiometer vhrr and advanced very high resolution radiometer avhrr and the landsat multispectral scanner mss and thematic mapper tm sensors were used to detect sea surface temperatures and suspended sediments shipboard measurements of temperature salinity and chlorophyll were acquired by the inner shelf transfer and recycling ishtar project and were compared to digitally enhanced and archived satellite images sea surface temperatures derived from satellite data were generally higher than field measurements this difference was the likely result of microscale stratification of the water column although other factors could have been involved also satellite data confirmed the known distribution of water masses in the region coachman et al 1975 upwelled water of oceanic origin anadyr water was visible as a cold surface plume running from anadyr strait north through western bering strait in the east warm alaskan coastal water was prominent along the alaskan coast including norton sound and the southeastern chukchi sea areal patterns of temperature salinity and phytoplankton distribution determined from field measurements agreed reasonably well with patterns of water mass distribution obtained from satellite images archived satellite images 1974 1978 were used to investigate the variability of the distribution of sea surface temperature and of the turbid plume of the yukon river alaskan coastal water acw first warms near the coast in june and the process extends seaward as summer progresses turbid water associated with discharge of the yukon river progresses in the same fashion extending northward across the entrance to norton sound maximum extent of the plume occurs in october anadyr water flows north through anadyr strait past st lawrence island its extent is variable depending on mesoscale pressure and local wind fields

east west differences in water mass nutrient and chlorophyll a distributions in the sea ice reduction region of the western arctic ocean 1 the r v mirai conducted hydrographic surveys in the western arctic ocean during summer 2004 across a front between cold arctic water and warm water from the pacific ocean where sea ice cover has been largely reduced in recent summers the hydrographic data indicate a new type of vertical temperature minimum water west of the front along isohaline surfaces with approximate salinity s of 32 which is fresher than the typical temperature minimum s 33 caused by spreading of pacific winter water pww mainly to the east of the front both of the temperature minimum waters are characterized by low potential vorticity with near freezing temperature suggesting that they are formed by winter convection with sea ice formation a difference between the waters results from a large contribution of sea ice meltwater to the fresh temperature minimum frtmin water of s 32 the distributions of the sea ice meltwater contribution and nitrogen deficit suggest that summer shelf water largely influenced by the sea ice melt in the chukchi sea is modified by winter convection on its way to the chukchi abyssal plain to form the frtmin water this water supplies nutrients through the water distribution to the west of the front at depths shallower than the nutrient maximum layer caused by the pww spreading the shallower nutrient supply by the frtmin water combined with light penetration without sea ice cover could produce a prominent chlorophyll a maximum layer west of the front

coexistence of nitrous oxide undersaturation and oversaturation in the surface and subsurface of the western arctic ocean the nitrous oxide n2o distributions in a shelf slope basin section from the chukchi sea shelf to the chukchi abyssal plain cap in the western arctic ocean were observed for the first time during the fourth chinese national arctic research expedition 4th chinare in late august 2010 the n2o concentrations were 11 4 16 9 nmol l 1 corresponding to saturation values of 92 118 in the surface water in the surface biological factor was negligible to n2o production and physical process dominated the surface n2o distribution the n2o undersaturation may be the result of dilution by sea ice meltwater the oversaturation may be caused by the diffusing of n2o rich shelf bottom water below the surface n2o concentrations ranged from 11 4 to 21 4 nmol l 1 on the chukchi sea shelf n2o concentrations increased from the surface to the near bottom water indicating sediment n2o produced by nitrification or denitrification emission may be a significant source the subsurface maxima in the upper halocline layer uhl may receive partial contribution from nitrification production but was primarily caused by the spreading of shelf water

the thermal stability of water ice at the poles of mercury recent radar observations of mercury have revealed the presence of anomalous radar reflectivity and polarization features near its north and south poles thermal model calculations show that despite mercury s proximity to the sun the temperatures of flat low reflectivity surfaces at mercury s poles are not expected to exceed 167 kelvin the locations of the anomalous polar radar features appear to be correlated with the locations of large high latitude impact craters maximum surface temperatures in the permanently shadowed regions of these craters are expected to be significantly colder as low as 60 kelvin in the largest craters these results are consistent with the presence of water ice because at temperatures lower than 112 kelvin water ice should be stable to evaporation over time scales of billions of years

radar images of mars full disk images of mars have been obtained with the use of the very large array vla to map the radar reflected flux density the transmitter system was the 70 m antenna of the deep space network at goldstone california the surface of mars was illuminated with continuous wave radiation at a wavelength of 3 5 cm the reflected energy was mapped in individual 12 minute snapshots with the vla in its largest configuration fringe spacings as small as 67 km were obtained the images reveal near surface features including a region in the tharsis volcano area over 2000 km in east west extent that displayed no echo to the very low level of the radar system noise the feature called stealth is interpreted as a deposit of dust or ash with a density less than about 0 5 gram per cubic centimeter and free of rocks larger than 1 cm across the deposit must be several meters thick and may be much deeper the strongest reflecting geological feature was the south polar ice cap which was reduced in size to the residual south polar ice cap at the season of observation the cap image is interpreted as arising from nearly pure co 2 or h 2o ice with a small amount of martian dust less than 2 percent by volume and a depth greater than 2 to 5 m only one anomalous reflecting feature was identified outside of the tharsis region although the elysium region was poorly sampled in this experiment and the north pole was not visible from earth

varieties of shallow temperature maximum waters in the western canadian basin of the arctic ocean the properties and spreading pathways of shallow temperature maximum waters stms in the western canadian basin are investigated using ctd and mooring data obtained in 1997 98 as part of the sheba surface heat budget of the arctic ocean drift experiment and available historical data three distinct varieties of stm are recognized on the basis of salinity range 1 surface mixed layer water smlw with s 32 psu these stms carry sufficient heat within the upper layers of the ocean to significantly affect the rates of ice cover and decay for example during the winter of 1997 98 anomalously warm stm 0 c originating from ecsw was observed to spread northwards along the northwind ridge and chukchi plateau where the maximum reduction of the ice covers was subsequently observed in late summer 1998 maslanik et al 1999 regional climate variability and ice cover in the western canadian basin are thus affected not only by anomalous atmospheric circulation patterns but also by the circulation of upper ocean water masses

distribution of dissolved organic matter in the eastern bering sea chukchi sea barrow canyon and beaufort sea 1 the distribution of dissolved organic carbon doc in the western arctic ocean is greatly influenced by conservative riverine doc flux into the northern bering sea bering strait and beaufort sea as indicated by an inverse correlation with salinity based on the relations between doc salinity and seawater temperature several water masses could be identified these included riverine water ice melt water surface mixed water cold and saline shelf water and atlantic ocean water high concentrations of chlorophyll a and doc were found in some parcels of dense shelf water in barrow canyon in addition labile doc compounds such as polyunsaturated fatty acids pufa were found in the dense shelf water suggesting the dense shelf water contains a product marine organic matter of the biological co2 pump

a search for water ice at the lunar poles with clementine images abstract optical and near ir signatures of water ice on the moon s surface were sought in the permanently shadowed regions near its poles significant amounts of multiply scattered radiation partly illuminate primary shadows cast by craters and other features if there is water ice in the permanently shadowed regions of the moon s surface its spectral signature should appear in this multiply scattered light this investigation can be done most effectively with observations obtained by spacecraft because most selenocentric positions occupied by the earth will also be occupied by the sun at some point in time and because the lunar poles are seen only obliquely to a terrestrial observer images obtained by clementine are particularly well suited to this task because the spacecraft s polar orbit allowed images of the poles to be acquired on nearly every orbit resulting in literally thousands of images taken within a few degrees of each pole and because the filters on the ultraviolet visual camera uvvis and the near infrared camera nir occur at major absorption bands or within important continuum features of water ice approximately 5800 images obtained by the uvvis camera and 1800 images obtained by the nir camera were calibrated and combined into coadded mosaics to create multispectral maps of the lunar poles with the highest possible signal to noise unfortunately analysis of our uvvis mosaics indicates that any possible signal from multiply scattered light in primary shadows was overwhelmed by instrumental stray light for the nir camera we were able to determine the normalized reflectance of several regions that were identified by margot et al 1999 science284 1658 1660 as permanent shadows we have identified one permanently shadowed crater with a 1 5 m band spectral signature indicative of between 2 5 and 21 fractional coverage of h2o frost however the same region shows a 2 0 m spectral signature that is inconsistent with the presence of any water

the contribution of alaskan siberian and canadian coastal polynyas to the cold halocline layer of the arctic ocean numerous arctic ocean circulation and geochemical studies suggest that ice growth in polynyas over the alaskan siberian and canadian continental shelves is a source of cold saline water which contributes to the maintenance of the arctic ocean halocline the purpose of this study is to estimate for the 1978 1987 winters the contributions of arctic coastal polynyas to the cold halocline layer of the arctic ocean the study uses a combination of satellite oceanographic and weather data to calculate the brine fluxes from the polynyas then an oceanic box model is used to calculate their contributions to the cold halocline layer of the arctic ocean this study complements and corrects a previous study of dense water production by coastal polynyas in the barents kara and laptev seas recurrent polynyas form on the canadian and alaskan coasts from banks island to the bering strait and on the siberian coast from the bering strait to the new siberian islands in the bering sea polynyas form in norton sound south and west of st lawrence island and in the gulf of anadyr two regions that account for almost 50 of the total dense water production are the siberian coastal polynyas in the adjacent regions of the gulf of anadyr and anadyr strait and the alaskan coastal polynyas which occur along the coast from cape lisburne to point barrow for all of the western arctic coastal regions examined the mean annual total brine flux is 0 5 0 2 sv combination of this flux with the contribution from the barents kara and laptev seas which is recalculated from data in the earlier study shows that over the entire arctic coastal polynyas generate about 0 7 1 2 sv of dense water this compares well with the theoretical estimates of 1 1 5 sv because an unknown fraction of the barents kara and laptev brine flux must go to the eurasian basin deep water the coastal polynyas alone cannot renew the halocline layer other potential brine generation mechanisms include overall freezing on the shelves and the response of the ice to infrequent violent storms for example during february 1982 an intense storm generated a large region of low ice concentration in the eastern chukchi sea over barrow canyon the refreezing of the region was followed by the flow of a dense plume down barrow canyon although the ocean dynamical response to this refreezing needs to be established the possible response of a barrow canyon flow to this refreezing event suggests that the overall refreezing in response to infrequent violent storms may be a potential source of the additional brine needed to maintain the arctic ocean halocline

radar mapping of mercury full disk images and polar anomalies a random code technique has been used at arecibo to obtain delay doppler radar images of the full disk of mercury anomalously bright features were found at the north and south poles the north polar feature is oblong 4 by 8 and offset from the pole the smaller south polar feature is mostly confined to the floor of the crater chao meng fu the polar locations and radar properties of these features indicate that they may be produced by volume scattering in ice the images also reveal a variety of more subdued reflectivity features ranging in size from hundreds to thousands of kilometers some of these appear to have an impact origin

ground penetrating radar characterization and porosity evolution of an upper pleistocene oolite capped depositional cycle red bays northwest andros island great bahama bank abstract linkages among surface sediments depositional processes geomorphic forms stratigraphic architecture and pore distribution in bahamian sand bodies and oolite capped depositional successions have been characterized in recent studies an understanding of how these parameters especially porosity are preserved or modified in the eogenetic environment is essential in bridging the gap between modern and ancient analogs two complementary 3d 200 mhz and 400 mhz ground penetrating radar surveys and three shallow cores reveal that the uppermost part of the upper pleistocene marine isotope stage 5e lucayan formation at red bays andros island great bahama bank comprises a single 6 m thick upward shallowing parasequence six radar packages p1 p6 bounded by radar surfaces s1 s6 have been identified in the two 3d radar volumes the stratigraphic succession indicates development of a burrowed backshoal lagoon during early flooding of the bank top followed by deposition of flood tide driven low angle sheet sands and sigmoidal subaqueous dune deposits as the shelf margin sand shoal moved bankward as a function of continued sea level rise constructional accommodation on the front of the prograding subaqueous dune in the northwest part of the survey area and erosional accommodation created by downcutting of a shallow tidal channel into the upper part of the subaqueous dune depositional unit in the northeast part of the study area were filled with peloid and ooid dominated carbonate sands as sea level stabilized the uppermost radar package is a thin 0 15 to 0 55 m partially calichified carbonate sand sheet that mantles the entire survey site and that reflects late highstand and fall of sea level exposure of the studied interval to meteoric vadose diagenesis over the past 100 000 years has resulted in partial stabilization of the largely aragonitic precursor sediment through selective partial dissolution of aragonitic grains mainly ooid cortical layers peloids and mollusk shells accompanied by precipitation of patchily distributed low magnesium calcite cement core data demonstrate a relationship between stratigraphically controlled sedimentological attributes diagenesis and pore distribution three distinctive zones of porosity were present upon deposition a lower zone of relatively high interparticle porosity 21 3 to 33 2 in the medial part of p1 a low porosity zone

distribution of atlantic and pacific waters in the upper arctic ocean implications for circulation the atlantic and pacific oceans provide source waters for the arctic ocean that can be distinguished by their differing nitrate and phosphate concentration relationships using these relationships we estimate the amount of atlantic and pacific waters in the surface layer top 30 m of the arctic ocean atlantic source water is dominant in most of the eurasian basin and is present in significant amounts in the makarov basin north of the east siberian sea pacific source water is dominant in most of the canadian basin and is present in significant amounts in the amundsen basin north of greenland we deduce circulation patterns from the distributions of atlantic and pacific source waters in the surface layer of the arctic ocean and conclude that the flow within the surface layer differs from ice drift along the north american and european boundaries of the polar basin

iron distributions in the water column of the japan basin and yamato basin japan sea 1 in the japan and yamato basins japan sea dissolved fe d fe 0 22 m fraction was characterized by surface depletion mid depth maxima then a slight decrease with depth in deep water and uniform concentration in bottom waters because of biological uptake in the surface water and release by microbial decomposition of sinking organic matter in mid depth waters total fe concentrations t fe in the surface water of the japan sea were 1 4 nm a little higher than those in the surface waters of the nutrient deficient subtropical western north pacific and extremely higher than the nutrient rich subarctic western north pacific and the nutrient deficient subtropical central north pacific resulting from high atmospheric fe input to nutrient depleted surface water of the japan sea in the japan basin the t fe in bottom water were lower than those in deep water resulting from 1 the injection of new bottom water with the lower t fe into the japan basin bottom water 2 the particulate fe removal by particle scavenging during the bottom water circulation of the japan basin or 3 the injection of deep water with the higher t fe into the japan basin deep water on the other hand the t fe in deep water of the yamato basin and the slope regions were variable with different t fe levels among stations and depths we found a significant relationship between t fe and water transmittance in deep water probably resulting from the iron supply into the deep water because of the lateral transport of resuspended sediment from the slope

iron nutrients and humic type fluorescent dissolved organic matter in the northern bering sea shelf bering strait and chukchi sea 1 the concentrations of dissolved fe dfe total dissolvable fe humic type fluorescence intensity humic f intensity as humic type fluorescent dissolved organic matter humic type fdom and nutrients were determined vertically in the northern bering sea shelf yukon river estuary region and st lawrence island polynya region the eastern chukchi sea shelf chukchi shelf polynya region and the central bering strait during 30 july to 12 august 2007 and 30 june to 12 july 2008 in early july 2008 with a nearly peak river water discharge period remarkably high humic f intensity and high dfe were found with a decrease in salinity s 26 30 in the surface water of the yukon river estuarine region these results suggest that riverine humic type fdom is responsible for dfe in coastal waters with natural organic ligand complexation of fe iii apparently playing an important role in iron transport to the northern bering sea shelf in the st lawrence island and chukchi shelf polynya regions cold dense waters t 1 5 to 1 7 c and 26 2 to 26 7 were found in deep and bottom waters the cold waters are characterized by high nutrient and iron concentrations and high humic f intensity probably resulting from two main processes brine rejection during sea ice formation and transport across the sediment water interface during early diagenesis in the central bering strait the waters are vertically uniform with high salinity s 32 5 and high nutrient and iron concentrations these waters appear to originate from the outer shelf of the bering sea and are not affected by denitrification occurring in bottom sediments of the bering shelf

freshwater budget of the canada basin arctic ocean from salinity δ18o and nutrients 1 the contribution of freshwater components e g meteoric sea ice and pacific water in the canada basin is quantified using salinity 18o and nutrient data collected in 2003 and 2004 the penetration depth of sea ice meltwater is limited to the upper 30 m and brine rejected during sea ice formation is observed from 30 to 250 m depth the fraction of meteoric water is high in the upper 50 m and decreases with depth pacific water entering via bering strait is the main source of freshwater below 50 m depth bering strait throughflow which transports pacific water with salinity 32 5 together with meteoric water supplied upstream of the bering strait contributes up to 75 of freshwater input 3200 km3 a 1 to the canada basin the mean residence time of pacific water in the canada basin is estimated to be 11 years precipitation and river runoff from both north american and eurasian continents add 800 km3 a 1 and sea ice formation removes 900 km3 a 1 0 6 m a 1 of fresh water the export of ice and liquid fresh water from the canada basin contributes 40 of the freshwater flux from the arctic ocean to the north atlantic ocean

comparing the vertical distribution of iron in the eastern and western north pacific ocean 1 labile dissolved fe 0 22 m in the western 165 e and eastern 165 w north pacific ocean had nutrient and apparent oxygen utilization aou like profiles characterized by surface depletion and deep enrichment 5 3000 m depth dissolved fe concentrations in the deep water column at the mid latitudes were approximately one half lower in the eastern region 0 5 0 8 nm than in the western region 0 8 1 3 nm although the dissolved fe concentrations in the surface mixed layer in both regions were extremely depleted to 0 1 0 2 nm surprisingly the labile particulate fe concentrations 0 1 nm total dissolvable fe minus labile dissolved fe throughout the water column at low latitudes in the eastern region were extremely lower than those 0 5 1 nm in the western region it is suggested that the low fe levels in the eastern mid latitude oceanic region are primarily due to the lower atmospheric fe supply in the eastern region

topography of the lunar south polar region implications for the size and location of permanently shaded areas we analyze clementine altimetry to constrain the size and location of proposed permanently shadowed regions in the vicinity of the lunar south pole long and short wavelength topography in the vicinity of the pole in combination with measurements of depths of well preserved craters and basins and the lunar topographic power spectrum have direct bearing on the nature of elevations in the south polar region a criterion based on geometric considerations and altimetry demonstrates that the existence of permanent shadowing is not very sensitive to the elevation of the south pole in addition permanent shadowing cannot be a consequence of large structures such as the south pole aitken basin and or a 300 km degraded polar basin perennially dark regions if they exist are most likely associated with craters or other axisymmetric features with diameters of at most 80 km centered at the pole for structures displaced 2 from the pole the maximum allowable diameter decreases to 30 km

spatial patterns of primary production on the shelf slope and basin of the western arctic in 2002 in the spring and summer of 2002 primary production in the chukchi sea was measured using 14 c uptake experiments our cruise track encompassed the shelf and continental slope area of the chukchi and beaufort seas progressing into deep water over the canada basin the study area experienced upwards of 90 ice cover during the spring with ice retreating into the basin during the summer production in the spring was light limited due to ice cover with average euphotic zone production rates of o0 3 g c m 2 d 1 values of 8 g c m 2 d 1 were observed in association with surface bloom conditions during the initial ice breakup considerable nutrient reduction in the surface waters took place between the spring and summer cruise and although not observed this was attributed to a spring bloom decreased ice cover and increased clarity of surface waters in the summer allowed greater light penetration the highest rates of production during the second cruise were found at 25 30 m coincident with the top of the nutricline daily euphotic zone productivity in the summer averaged 0 78 g c m 2 d 1 on the shelf and 0 32 g c m 2 d 1 on the edge of the canada basin these data provide an estimated annual production of 90 g c m 2 yr 1 in the study area

the continental margin is a key source of iron to the hnlc north pacific ocean here we show that labile particulate iron and manganese concentrations in the upper 500m of the western subarctic pacific an iron limited high nutrient low chlorophyll hnlc region have prominent subsurface maxima between 100 200 m reaching 3 nm and 600 pm respectively the subsurface concentration maxima in particulate fe are characterized by a more reduced oxidation state suggesting a source from primary volcagenic minerals such as from the kuril kamchatka margin the systematics of these profiles suggest a consistently strong lateral advection of labile mn and fe from redox mobilized labile sources at the continental shelf supplemented by a more variable source of fe from the upper continental slope this subsurface supply of iron from the continental margin is shallow enough to be accessible to the surface through winter upwelling and vertical mixing and is likely a key source of bioavailable fe to the hnlc north pacific

circulation of summer pacific halocline water in the arctic ocean 1 we present an analysis of arctic ocean hydrographic and sea ice observations from the 1990s with a focus on the circulation of water that originates in the north pacific ocean previous studies have shown the presence of two varieties of relatively warm summer halocline water in the vicinity of the chukchi sea i e the relatively fresh alaskan coastal water acw and the relatively saltier summer bering sea water sbsw here we extend these studies by tracing the circulation of these waters downstream into the arctic ocean we find that acw is generally most evident in the southern beaufort gyre while sbsw is strongest in the northern portion of the beaufort gyre and along the transpolar drift stream we find that this separation is most extreme during the early mid 1990s when the arctic oscillation was at historically high index values this leads us to speculate that the outflow to the north atlantic ocean through the canadian archipelago and fram strait may be similarly separated as arctic oscillation index values fell during the later 1990s acw and sbsw began to overlap in their regions of influence these changes are evident in the area north of ellesmere island where the influence of sbsw is highly correlated with a 3 year lag with the arctic oscillation index we also note the presence of winter bering sea water wbsw which underlies the summer varieties all together this brings the number of distinct pacific water types in our arctic ocean inventory to three acw sbsw and wbsw

lunar cold traps effects of double shielding abstract this paper deals with the problem of water permanence on the surface of the moon possible zones where water ice can survive are called cold traps k watson b c murray and h brown 1961 j geophys res 66 3033 3045 these are zones of the moon permanently obscured where the temperatures are low enough to preserve ice for billions of years in this work we developed a model for the topographic temperatures of complex craters whose shape was approximated by a capsized frustum of a circular right cone double shaded areas were simulated by embedding a small hemispherical crater in the shadowed part of the previous one their temperatures were calculated using the r r hodges jr 1980 proc lunar planet sci conf 11th 2463 2477 model first we verified that our results were in agreement with those of previous models our results confirm those obtained by j r salvail and f p fanale 1994 icarus 111 441 445 and in agreement with hodges 1980 we found that the lowest temperatures are reached by tycho like craters that are the larger and shallower among the examined cases when small craters are embedded in the shaded area of larger ones their temperatures are low enough to preserve other volatiles like co 2 hodges 1980 in particular if we consider double shaded areas in biot like craters the temperatures are lower than 103 k in a shell of almost 20 around the poles thus allowing the preservation of ices for geometrical reasons a hemispherical crater embedded in the bottom of a biot like crater cold remain in the shadowed area for latitude values lower than those reached by an analogous crater embedded in sosigene or tycho like craters therefore the latitudinal radius of polar frost caps could be greater than that predicted by previous models that did not consider double shaded areas however double shielding occurs in only a fraction of the secondary craters therefore in this case eventual deposits of ice would be of smaller dimensions compared with the case of primary shielding analysis of the clementine radar data s nozette c l lichtenberg p spudis r bonner w ort e malaret m robinson and e m shoemaker 1996 science 274 5292 5300 and the lunar prospector neutron spectrometer data seems to be consistent with the presence of water ice in very low concentrations across a significant number of craters thus confirming the old hypothesis of watson et al 1961

the role of soluble fe iii in the cycling of iron and sulfur in coastal marine sediments in marine sediments fe iii is found predominantly as a solid recently however soluble species of fe3 complexed by natural organic ligands have been detected in coastal marine sediments with voltammetric microelectrodes the role of soluble fe3 complexes in diagenesis is unknown in anoxic conditions soluble fe3 can effectively oxidize fes2 and recycle iron and sulfur for use as terminal electron acceptors during natural organic matter nom degradation alternatively soluble fe3 complexes can catalyze the formation of fes and fes2 through the rapid chemical reduction of fe3 by dissolved sulfide to better understand the role of soluble fe3 in the transformation of iron and sulfur in marine sediments we incubated the first few centimeters of unvegetated salt marsh sediment in plug flow reactors microbial iron reduction seemed to prevail in suboxic conditions but sulfate reduction outcompeted microbial iron reduction in the presence of reactive organic metabolites the dominance of sulfate reduction led to the complete removal of reactive iron oxides by precipitation of fes experiments mimicking the enrichment of soluble fe3 complexes in reduced sediments show that soluble fe3 does not reoxidize fes and pyrite rather it promotes pyrite precipitation by enhancing sulfate reduction via complex bacterial interactions the rate of pyrite formation in the presence of soluble fe3 is much higher than previously reported in the literature suggesting that soluble fe3 might promote alternative pathways for microbial degradation of nom that ultimately results in the immobilization of fe and s as reduced iron sulfide minerals

understanding the origin and evolution of water in the moon through lunar sample studies a paradigm shift has recently occurred in our knowledge and understanding of water in the lunar interior this has transpired principally through continued analysis of returned lunar samples using modern analytical instrumentation while these recent studies have undoubtedly measured indigenous water in lunar samples they have also highlighted our current limitations and some future challenges that need to be overcome in order to fully understand the origin distribution and evolution of water in the lunar interior another exciting recent development in the field of lunar science has been the unambiguous detection of water or water ice on the surface of the moon through instruments flown on a number of orbiting spacecraft missions considered together sample based studies and those from orbit strongly suggest that the moon is not an anhydrous planetary body as previously believed new observations and measurements support the possibility of a wet lunar interior and the presence of distinct reservoirs of water on the lunar surface furthermore an approach combining measurements of water abundance in lunar samples and its hydrogen isotopic composition has proved to be of vital importance to fingerprint and elucidate processes and source s involved in giving rise to the lunar water inventory a number of sources are likely to have contributed to the water inventory of the moon ranging from primordial water to meteorite derived water ice through to the water formed during the reaction of solar wind hydrogen with the lunar soil perhaps two of the most striking findings from these recent studies are the revelation that at least some portions of the lunar interior are as water rich as some mid ocean ridge basalt source regions on earth and that the water in the earth and the moon probably share a common origin

some controls on flow and salinity in bering strait 1 during 1993 1994 steric forcing of flow through bering strait represented a northward sea level drop of 0 7 m from the bering sea basin to the adjacent deep arctic ocean of which 2 3 was due to the salinity difference between the basins seasonal variability of steric forcing appears small 0 05 m in contrast to large seasonal wind effects interannual changes in steric forcing may exceed 20 however and warm inflow from the north atlantic accumulation of freshwater in the southwest canada basin and temperature and salinity changes in the upper bering sea have all contributed to recent changes the mean salinity balance in bering strait is primarily maintained by large runoff to the bering shelf dilute coastal inflow from the gulf of alaska and on shelf movement of saline and nutrient rich oceanic waters from the bering sea basin in bering strait therefore both the throughflow and its salinity are affected by remote events

vertical distributions of iron iii hydroxide solubility and dissolved iron in the northwestern north pacific ocean detailed vertical distributions of fe iii hydroxide solubilities and dissolved fe concentrations which are strongly related to the concentration and affinity of natural organic fe iii chelators in seawater were measured at three typical stations in the northwestern north pacific ocean iron iii hydroxide solubility in the surface mixed layer was generally high and variable 0 3 2 4 nm corresponding with the depth of high chlorophyll a concentrations and the solubility minima 0 2 0 4 nm occurred at 75 125 m depth the vertical profiles of fe iii hydroxide solubility in mid depth and deep waters are characterized by mid depth maxima 0 6 0 7 nm and subsequently a slight decrease to 0 4 0 5 nm with depth which is markedly similar to nutrient and dissolved fe depth profiles the solubility profiles reveal that dissolved fe concentrations in deep ocean waters are controlled primarily by the fe iii complexation with natural organic ligands which were released through the oxidative decomposition and transformation of biogenic organic matter in mid depth and deep waters