post glacial relative sea level isostasy and glacial history in icy strait southeast alaska usa abstract we use the radiocarbon ages of marine shells and terrestrial vegetation to reconstruct relative sea level rsl history in northern southeast alaska rsl fell below its present level around 13 900 cal yr bp suggesting regional deglaciation was complete by then rsl stayed at least several meters below modern levels until the mid holocene when it began a fluctuating rise that probably tracked isostatic depression and rebound caused by varying ice loads in nearby glacier bay this fluctuating rsl rise likely reflects the episodic but progressive advance of ice in glacier bay that started around 6000 cal yr bp after that time rsl low stands probably signaled minor episodes of glacier retreat thinning that triggered isostatic rebound and land uplift progressive down fjord advance of the glacier bay glacier during the late holocene is consistent with the main driver of this glacial system being the dynamics of its terminus rather than climate change directly only after the glacier reached an exposed position protruding into icy strait ca ad 1750 did its terminus succumb a century before the climate changes that marked the end of the little ice age to the catastrophic retreat that triggered the rapid isostatic rebound and rsl fall occurring today in icy strait

changing atmospheric δ14c and the record of deep water paleoventilation ages we propose a new calculation method to better estimate the deep water ventilation age from benthic planktonic foraminifera 14 c ages our study is motivated by the fact that changes in atmospheric 14 c through time can cause contemporary benthic and planktonic foraminifera to have different initial 14 c values this effect can cause spurious ventilation age changes to be interpreted from the geologic data using a new calculation method 14 c projection ages we recalculate the data from the pacific ocean contrary to previous results we find that the pacific intermediate and deep waters were about 600 years older than today at the last glacial maximum in addition there are possible signals of ventilation age change prior to ice sheet melting and at the younger dryas however the data are still too sparse to constrain these ventilation transients

mars residual north polar cap earth based spectroscopic confirmation of water ice as a major constituent and evidence for hydrated minerals a new reflectance spectrum of the martian north polar cap is analyzed and it shows water ice absorption features this evidence confirms the result of the viking irtm and mawd experiments which indicate that the north residual polar cap of mars is composed of water ice during the season observed northern hemisphere spring ls 50 the spectra presented here show that other materials are probably present as well these other materials may be hydrated minerals as indicated by weak absorptions in the spectrum at 1 9 2 3 and possibly 1 4 m but the materials seem to be otherwise spectrally bland

patterns of deglacial warming in the pacific ocean a review with emphasis on the time interval of heinrich event 1 abstract based on a compilation of currently available records of past sea surface temperature sst variability estimated from a variety of different proxies the regional scale deglacial sst development in the pacific ocean is tentatively classified into four endmember types the subtropical and tropical pacific is characterized by a continuous deglacial warming without marked interruption during the time interval of heinrich event 1 h1 whereas the subarctic north pacific exhibits centennial scale warm cold oscillations during this time interval sst records from marginal seas of the pacific show a deglacial warming interrupted by a cooling event coeval with h1 followed by a marked bolling sst increase a single sst record from the southwestern subantarctic pacific displays a continuous deglacial warming across h1 followed by an antarctic cold reversal type cooling during the allerod thus in contrast to the deglacial sst development in the atlantic which has been inferred to be overwhelmingly driven by the redistribution of heat through changes in the meridional overturning circulation moc none of the open oceanic pacific sst records reviewed here displays any obvious and or dominant response to the reduction of the moc and or the reorganization of atmospheric circulation during h1 within the limits of absolute chronologies all tropical and subtropical pacific sst records show an onset of deglacial warming at 19 1 ka coeval with the onset of the deglacial rise in sea level

consistent relationship between global climate and surface nitrate utilization in the western subarctic pacific throughout the last 500 ka 1 the open subarctic pacific is at present a high nitrate low chlorophyll hnlc region where nitrate is perennially abundant at the surface theoretically the hnlc status of this region is subject to modification by ocean circulation and or micronutrient supply with implications for the effectiveness of the biological pump and hence carbon sequestration in the ocean interior records of biogenic detritus in sediments from throughout the subarctic pacific indicate that export production was generally lower during glacial maxima while nitrogen isotope measurements from the bering sea have shown that nitrate consumption there was more complete during the last glacial period than it is today here nitrogen isotopic analyses of bulk sediments 15nbulk from three deep water sites in the open subarctic pacific are evaluated in terms of regional nitrate isotopic composition and local relative nitrate utilization the eastern subarctic pacific 15nbulk record bears great similarity to 15nbulk records from the western margin of north america over the last glacial cycle suggesting that variability in the isotopic composition of subeuphotic zone nitrate the growth substrate is reasonably coherent throughout the northeast pacific and dominates at these sites however the two western subarctic pacific records which lie at the heart of the hnlc region display a different pattern implying that significant changes in local relative nitrate utilization overlie the regional background variability after a novel correction intended to remove the background signal associated with denitrification in the eastern tropical north pacific these nitrate utilization records are correlated with a benthic oxygen isotope stack reflecting global deep ocean temperature and ice volume r2 0 65 the correlation implies a strong link between global climate and subarctic pacific nitrate utilization with nearly complete nitrate consumption during glacial periods when export production was low

evidence from diatom bound nitrogen isotopes for subarctic pacific stratification during the last ice age and a link to north pacific denitrification changes higher diatom bound d 15 n 70 wt lower opal content and 1200 ppm lower biogenic barium taken together and with constraints on sediment accumulation rate these results suggest a reduced supply of nitrate to the surface due to stronger stratification of the upper water column of the bering sea during glacial times with more complete nitrate consumption resulting from continued iron supply through atmospheric deposition this finding extends the body of evidence for a pervasive link between cold climates and polar ocean stratification in addition we hypothesize that more complete nutrient consumption in the glacial age subarctic pacific contributed to the previously observed ice age reduction in suboxia and denitrification in the eastern tropical north pacific by lowering the nutrient content of the intermediate depth water formed in the subpolar north pacific in the deglacial interval of the bering sea record two apparent peaks in export productivity are associated with maxima in diatom bound and bulk sediment d 15 n the high d 15 n in these intervals may have resulted from greater surface nutrient consumption during this period however the synchroneity of the deglacial peaks in the bering sea with similar bulk sediment d 15 n changes in the eastern pacific margin and the presence of sediment lamination within the bering sea during the deposition of the productivity peaks raise the possibility that both regional and local denitrification worked to raise the d 15 n of the nitrate feeding bering sea surface waters at these times

freshwater impacts recorded in tetraunsaturated alkenones and alkenone sea surface temperatures from the okhotsk sea across millennial scale cycles 1 we present records of phytoplankton produced alkenones down a long piston core which reveal changes of sea surface temperature sst and sea surface salinity sss in the southwestern okhotsk sea over the past 120 ka between 20 and 60 ka b p alkenone derived temperatures typically increased by 6 c 8 c from periods corresponding within a few hundred years to stadials to those corresponding to interstadials recorded in greenland ice cores the abundance of c37 4 alkenone relative to total c37 alkenones percent c37 4 a possible proxy for salinity indicated that during most low sss was associated with high sst the warm freshwater events might be related to 1 a decline in the supply of saline water entering the okhotsk sea through the soya strait 2 strengthening of the freshwater supply from the amur river and precipitation over the okhotsk sea associated mainly with increased asian summer monsoon activity and 3 the effect of melting sea ice these findings increase our understanding of the close linkage between high and low latitudes in relation to climate change and the synchronicity of climate changes within a few centuries between the pacific and the atlantic sides of the northern hemisphere

a 15 000 year paleoenvironmental record from meiji seamount far northwestern pacific late glacial and holocene hemipelagic sediments from meiji seamount in the far northwest pacific contain common to abundant planktonic and benthic foraminifera for ams 14c dating for stable isotope analysis and for interpreting paleoclimate change we present here chronostratigraphic faunal and geochemical results from a piston core which indicate that during glacial times as young as 14 000 yrs bp the northwest pacific sea surface salinity was at least as low as today effectively inhibiting convective overturn between 12 000 and 13 000 yrs ago after a major flux of ice rafting there is faunal and 18o evidence of an abrupt decrease in surface ocean salinity coincident with this event was an increase in biological productivity shown by higher fluxes of calcium carbonate organic carbon opal and greater abundances and lower 13o of the benthic foraminifera uvigerina oxygen isotope ratios in uvigerina and cibicidoides show step like decreases at about 13 000 14 000 11 000 10 000 and 6000 8000 yrs bp these events may be analogous to steps in the north atlantic 18o record during meltwater events if this interpretation is correct then the temperature and salinity history of the deep pacific lags that of the north atlantic by about 1000 yrs consistent with the transport time of deep water from the north atlantic to the north pacific

glacial flour dust storms in the gulf of alaska hydrologic and meteorological controls and their importance as a source of bioavailable iron 1 iron is an essential micronutrient that limits primary productivity in much of the ocean including the gulf of alaska goa however the processes that transport iron to the ocean surface are poorly quantified we combine satellite and meteorological data to provide the first description of widespread dust transport from coastal alaska into the goa dust is frequently transported from glacially derived sediment at the mouths of several rivers the most prominent of which is the copper river these dust events occur most frequently in autumn when coastal river levels are low and riverbed sediments are exposed the dust plumes are transported several hundred kilometers beyond the continental shelf into iron limited waters we estimate the mass of dust transported from the copper river valley during one 2006 dust event to be between 25 80 ktons based on conservative estimates this equates to a soluble iron loading of 30 200 tons we suggest the soluble fe flux from dust originating in glaciofluvial sediment deposits from the entire goa coastline is two to three times larger and is comparable to the annual fe flux to goa surface waters from eddies of coastal origin given that glaciers are retreating in the coastal goa region and in other locations it is important to examine whether fluxes of dust are increasing from glacierized landscapes to the ocean and to assess the impact of associated fe on marine ecosystems

northward and southward migrations of frontal zones during the past 40 kyr in the kuroshio oyashio transition area 1 the variation of sea surface temperature sst in the kuroshio oyashio transition area and the okhotsk sea during the last 40 kyr was estimated using long chain unsaturated alkyl ketones alkenones the temperature difference between the present and the last glacial period was about 5 6 c in the kuroshio oyashio transition area slightly larger than the 4 c previously reported moreover alkenones were not detected before 18 kyr b p in or near the okhotsk sea perhaps because of nearly year round sea ice expansion which would have prevented the growth of alkenone producers or because alkenones were less well preserved in surface sediments during the glacial period the northward and southward migrations of frontal zones were evaluated using differences in alkenone temperatures between stations located in the vicinity of the subarctic front saf subarctic boundary sab and kuroshio bifurcation front kbf all three frontal zones migrated southward during the glacial period compared with their present positions and their relative positions were different between the holocene and glacial periods in particular the distance between the saf and the sab was reduced during the glacial period compared with at present the northward and southward migration of the frontal zones may relate to both mid to low atmospheric circulation and polar atmospheric circulation

glacial holocene environment of the southeastern okhotsk sea evidence from geochemical and palaeontological data abstract environmental conditions and productivity changes in the southeastern okhotsk sea have been reconstructed for the last 20 ka using planktonic and benthic foraminiferal oxygen isotope records and calcium carbonate organic carbon and opal content data from two sediment cores species variability in benthic foraminiferal and diatom assemblages provides additional palaeoceanographic evidence ams radiocarbon dating of the sediments and oxygen isotope stratigraphy serve as the basis for the age models of the cores for the last 20 14 c kyr and for correlation between environmental variations in the okhotsk sea and regional and global climate changes benthic foraminiferal assemblages in the two cores depth 1590 and 1175 m varied with time so that we could recognise seven zones with different species composition changes in the benthic foraminiferal assemblages parallel major environmental and productivity variations during the last glaciation fluxes of organic matter to the sea floor showed strong seasonal variations indicated by the presence of abundant a weddellensis and infaunal uvigerina spp benthic foraminiferal assemblages changed with warming at 12 5 11 and 10 8 14 c kyr bp when productivity blooms and high organic fluxes were coeval with global meltwater pulses 1a and 1b younger dryas cooling caused a decline in productivity 11 10 kyr bp affecting the benthic faunal community subsequent warming triggered intensive diatom production opal accumulation and a strong oxygen deficiency causing significant changes in benthic fauna assemblages from 5 26 4 4 kyr bp to present time

230th normalization an essential tool for interpreting sedimentary fluxes during the late quaternary there is increasing evidence indicating that syndepositional redistribution of sediment on the seafloor by bottom currents is common and can significantly affect sediment mass accumulation rates notwithstanding its common incidence this process generally referred to as sediment focusing is often difficult to recognize if redistribution is near synchronous to deposition the stratigraphy of the sediment is not disturbed and sediment focusing can easily be overlooked ignoring it however can lead to serious misinterpretations of sedimentary fluxes particularly when past changes in export flux from the overlying water are inferred in many instances this problem can be resolved at least for sediments deposited during the late quaternary by normalizing to the flux of 230th scavenged from seawater which is nearly constant and equivalent to the known rate of production of 230th from the decay of dissolved 234u we review the principle advantages and limitations of this method notwithstanding its limitations it is clear that 230th normalization does provide a means of achieving more accurate interpretations of sedimentary fluxes and eliminates the risk of serious misinterpretations of sediment mass accumulation rates

intermittent existence of a southern californian upwelling cell during submillennial climate change of the last 60 kyr 1 application of a high resolution multiproxy approach to a sedimentary section drilled at ocean drilling program site 1017 located under a highly active upwelling cell off point conception california provides clear evidence for surface ocean productivity shifts on submillennial timescales during the last 60 kyr the proxies include bulk sediment major and minor elements organic carbon and carbonate concentrations 15n and planktonic foraminiferal species assemblage and carbon isotope determinations the collective results demonstrate that marine productivity in this area was not simply linearly related to cold and warm cycles except during the millennial scale climate oscillations of marine isotope stage mis 3 during that interval the upwelling cell and resulting high productivity were active during warm interstadial events and were largely inactive during cool stadial events however the last glacial maximum was also relatively productive productivity increased dramatically during the bolling warm interval while the allerod and younger dryas were much less productive high coccolithophorid abundance commenced during the earliest holocene after 10 ka the complexity of the productivity response was probably related to interplay between local winds as well as california undercurrent strength

intensification of the oxygen minimum zone in the northeast pacific off vancouver island during the last deglaciation ventilation and or export production 1 the oxygen minimum zone omz off vancouver island was more oxygen depleted relative to modern conditions during the allerod 13 5 to 12 6 calendar kyr and again from 11 to 10 kyr the timing of omz intensification is similar to that seen throughout the north pacific although the onset appears to have been delayed by 1500 years off vancouver island radiocarbon dating of coeval benthic and planktonic foraminifera shows that between 16 0 and 12 6 kyr the age contrast between surface and intermediate waters 920 m depth off vancouver island was similar to or slightly less than that today there is no evidence of an increased age difference i e decreased ventilation during the deglaciation particularly during the allerod however sedimentary marine organic carbon concentration and mass accumulation rate increased substantially in the allerod suggesting that increased organic matter export was the principal cause of late pleistocene omz intensification off vancouver island

biogenic opal indicating less productive northwestern north pacific during the glacial ages 1 biogenic opal and ice rafted detritus ird data from sediments in the okhotsk sea and the neighboring north pacific revealed the remarkable reduction in opal production and southward advancement of sea ice covered area during the last glacial maximum resulting also southward shift of high biological productive area in the northwestern north pacific it implies that the substantial reduction in outflux of co2 to the atmosphere in northwestern north pacific and the pronounced increase in co2 sequestering in temperate north pacific this could be an additional co2 reduction mechanism of atmospheric co2 in the last glacial period

brachiopods recording seawater temperature a matter of class or maturation calcite fibres of the innermost secondary layer of low magnesium calcite brachiopod shells are in oxygen isotope equilibrium with ambient seawater previous work on terebratalia transversa indicates that the first formed calcite fibres of the secondary layer are not in isotopic equilibrium while the later fibres of mature valves are in oxygen isotope equilibrium with seawater here secondary ion mass spectrometry sims analyses reveal that this trend of oxygen isotope equilibrium being attained towards the innermost shell rather than being a feature throughout the secondary layer occurs in brachiopods from two orders and two sub orders this suggests a general pattern among brachiopods with low magnesium calcite shells and leads to the recommendation that only the innermost fibres of mature valves be included in proxy calculations of seawater temperature although the trend is common in the three species studied here the extent of the isotopic range is much less marked in the species that lacks punctae

environmental change in the sea of okhotsk during the last 1 1 million years on the basis of two sedimentary records from the central sea of okhotsk we reconstruct the closely coupled glacial interglacial changes in terrigenous flux marine productivity and sea ice coverage over the past 1 1 myr the correspondance of our sedimentary records to the china loess grain size record china loess particle timescale chiloparts suggests that environmental changes in both the sea of okhotsk area and in se asia were closely related via the siberian atmospheric high pressure cell during full glacial times our records point to a strong siberian high causing northerly wind directions the extension of the sea ice cover and a reduced amur river discharge deglacial maxima of terrigenous flux were succeeded by or synchronous to high productivity events marine productivity was strengthened during glacial terminations because of an effective nutrient utilization at times of enhanced water column stratification and high nutrient supply from fluvial runoff and sea ice thawing during interglacials se monsoonal winds prevailed analogous to today s summer situation of a pronounced mongolian heat low and a strong hawaiian high strong freshwater discharge induced by high precipitation rates in the amur drainage area and a seasonally reduced and mobile sea ice cover favored marine productivity although being considerably lower than during the terminations and a lowered flux of ice rafted detritus

inputs of glacially derived dissolved and colloidal iron to the coastal ocean and implications for primary productivity 1 glacial meltwaters draining shield bedrock under the greenland ice sheet gis contain 0 4 m total dissolved fe tdfe with an average flow weighted concentration of 53 nm the concentrations of 0 03 and 0 03 0 4 m fe vary over the ablation period with weighted means for each of these fractions being respectively 22 4 nm and 30 8 nm these concentrations are lower estimates as an adjacent larger glacier a more representative source of glacial meltwater had higher dissolved fe concentrations and reactions of meltwaters with proglacial sediments could also enhance dissolved fe concentrations this source of tdfe is additional to the reactive oxyhydr oxide phases identified by raiswell et al 2006 that are also introduced to adjacent polar seas from glaciers the fe concentrations in the shield bedrock underlying the gis are lower than those of other crustal rocks 4 0 cf 6 2 but we argue that these fe concentrations are not limiting on the total dissolved fe concentrations we measure the biogeochemical weathering processes operating on the subglacial debris and suspended sediment in our catchment are likely to be similar to those in other glaciated catchments therefore the meltwater fe concentrations reported here can be used to give a first estimate of global fluxes of meltwater dissolved fe to coastal polar waters a lower estimate of the global flux of tdfe from glacial meltwaters is 75 106 moles fe a this glacial meltwater input of fe to adjacent polar waters will be greatest around greenland where there are highest annual meltwater discharges however the greatest impact of this source of glacial meltwater fe is anticipated to be in antarctic high nutrient low chlorophyll hnlc waters where phytoplankton productivity is typically limited by availability of fe for antarctic waters the estimated meltwater fe tdfe input is about 10 of that suggested to come from sea ice melting but glacial inputs continue throughout the austral summer ablation period after sea ice melt is complete

radiocarbon age anomaly at intermediate water depth in the pacific ocean during the last deglaciation 1 benthic and planktonic 14c ages are presented for the last glacial termination from marine sediment core vm21 30 from 617 m in the eastern equatorial pacific the benthic planktonic 14c age differences in the core increased to more than 6000 years between heinrich 1 time and the end of the younger dryas period several replicated 14c ages on different benthic and planktonic species from the same samples within the deglacial section of the core indicate a minimal amount of bioturbation scanning electron microscopy reveals no evidence of calcite alteration or contamination the oxygen isotope stratigraphy of planktonic and benthic foraminifera does not indicate anomalously old glacial age values and there is no evidence of a large negative stable carbon isotope excursion in benthic foraminifera that would indicate input of old carbon from dissociated methane it appears therefore that the benthic 14c excursion in this core is not an artifact of diagenesis bioturbation or a pulse of methane a benthic 14c stratigraphy reconstructed from the 14c ages from the deglacial section of vm21 30 appears to match that of baja margin core mv99 mc19 gc31 pc08 705 m but the magnitude of the low 14c excursion is much larger in the vm21 30 record this would seem to imply that the vm21 30 core was closer to the source of 14c depleted waters during the deglaciation but the source of this co2 remains elusive

iron flux induced by haida eddies in the gulf of alaska 1 mesoscale anticyclonic haida eddies are proposed to deliver a substantial amount of iron into the gulf of alaska goa central gyre where surface waters experience high nitrate low chlorophyll conditions in this study we calculate an averaged upwelling flux of dissolved iron into the euphotic zone 100 m of 1 17 mol m 2 d 1 based on observed iron profiles and modeled eddy dynamics and resultant vertical velocities this estimated eddy derived iron supply rate is comparable with new estimates of pulsed iron fertilization rates from rare volcanic ash deposition events despite the relatively small area affected by haida eddies they are estimated to contribute about 4 6 106 moles of dissolved iron yearly to the goa which is equivalent to the annual atmospheric dust deposition haida eddies therefore represent a major iron source that should strongly influence the regional biological productivity and carbon budget of the goa

paleonutrient and productivity records from the subarctic north pacific for pleistocene glacial terminations i to v our study addresses fundamental questions of the mode and timing of orbital and millennial scale changes in the meridional overturning circulation moc of the subarctic north pacific particular concerns are the vertical mixing the present and past abundance of nutrients in surface waters despite strong stratification and the north pacific north atlantic seesaw of oscillations in sea surface temperature sst we do this by generating and interpreting multiple records for glacial terminations i v down two long piston cores one each from the western and eastern subarctic pacific chlorins and biogenic opal are proxies for surface water productivity delta 13 c of epibenthic foraminifera is a record of deepwater ventilation and the delta 13 c of n pachyderma sin is a tracer of nutrients in subsurface waters that extend up to the sea surface during times of vertical mixing the degree of mixing is traced by pairing sst and delta 18 o records of planktic surface and subsurface pycnocline dwellers tight age control is deduced from a suite of age calibrated 14 c plateau boundaries for termination i and benthic delta 18 o and geomagnetic events for the last 800 ka carbon 14 paleoreservoir ages record the ages of surface and deep waters to uncover short term changes in moc over termination i we have defined a standard sequence of short term productivity events for termination i also evident during terminations ii to v and subsequent interglacials over the last 450 ka the peak glacial regime of stable stratification and low productivity terminated together with the end of ice rafting and melting near 17 ka similar to 2000 years after the onset of termination i pulses of vertical mixing and incursion of warm surface waters from the subtropics followed convected young water masses finally penetrated down to 3600 m water depth at 17 0 to less than 14 5 ka significantly improving bottom water ventilation through the late deglacial and earliest interglacial mixing with upwelled nutrients from the pycnocline induced short term maxima in algal production of chlorins and biogenic opal near 17 15 and 15 12 ka respectively deglacial meltwater incursions in the aleutian current and silica input from north american rivers also promoted east pacific productivity after 15 5 ka productivity decreased during the late deglacial and early interglacial coeval with an exceptional peak in caco 3 preservation caused by both low organic flux and well ventilated deepwater subsequently low salinity and cool surface waters and in turn stratification were gradually restored a second opal dominated productivity maximum marked the ends of interglacials the deglacial pulses of vertical mixing around 17 11 ka imply an important contribution of the north pacific to the coeval release of oceanic co 2 into the atmosphere and support the east west seesaw model of climate change

the deglacial transition on the southeastern alaska margin meltwater input sea level rise marine productivity and sedimentary anoxia 1 oxygen isotope data from planktonic and benthic foraminifera on a high resolution age model 44 14c dates spanning 17 400 years document deglacial environmental change on the southeast alaska margin 59 33 32 n 144 9 21 w 682 m water depth surface freshening i e 18o reduction of 0 8 began at 16 650 170 cal years b p during an interval of ice proximal sedimentation likely due to freshwater input from melting glaciers a sharp transition to laminated hemipelagic sediments constrains retreat of regional outlet glaciers onto land circa 14 790 380 cal years b p abrupt warming and or freshening of the surface ocean i e additional 18o reduction of 0 9 coincides with the bolling interstade of northern europe and greenland cooling and or higher salinities returned during the allerod interval coincident with the antarctic cold reversal and continue until 11 740 200 cal years b p when onset of warming coincides with the end of the younger dryas an abrupt 1 reduction in benthic 18o at 14 250 290 cal years b p likely reflects a decrease in bottom water salinity driven by deep mixing of glacial meltwater a regional megaflood event or brine formation associated with sea ice two laminated opal rich intervals record discrete episodes of high productivity during the last deglaciation these events precisely dated here at 14 790 380 to 12 990 190 cal years b p and 11 160 130 to 10 750 220 cal years b p likely correlate to similar features observed elsewhere on the margins of the north pacific and are coeval with episodes of rapid sea level rise remobilization of iron from newly inundated continental shelves may have helped to fuel these episodes of elevated primary productivity and sedimentary anoxia

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

british columbian continental shelf as a source of dissolved iron to the subarctic northeast pacific ocean 1 the distribution of dissolved 0 4 m iron fe across the continental shelf and slope of queen charlotte sound on the west coast of canada was examined to estimate the potential of these waters as a source of fe to the fe limited waters of the subarctic northeast pacific iron profiles obtained in shelf slope and offshore waters demonstrate decreasing concentrations of fe with distance from the continent within 50 m of the shelf sediments dissolved fe concentrations were 5 3 0 3 nm this signal was detected although attenuated by 80 along the isopycnal surface at offshore stations 40 50 km seaward of the shelf break strongly suggesting cross shelf transport of an fe rich plume originating in low dissolved oxygen 3 ml l 1 130 mol kg 1 waters in subsurface water over the continental shelf several physical mechanisms that may cause these fe enriched waters to advect offshore in this region i e tidal currents and ekman transport in the bottom boundary layer coastal downwelling relaxation from upwelling and the formation of anticyclonic westward propagating coastal eddies are discussed we suggest that strong tidal currents over broad continental shelves may play a key role in fe supply to ocean basins

controls on deglacial changes in biogenic fluxes in the north pacific ocean the subarctic north pacific ocean holds a large co2 reservoir that is currently isolated from the atmosphere by a low salinity layer it has recently been hypothesized that the reorganization of these high co2 waters may have played a crucial role in the degassing of carbon dioxide to the atmosphere during the last deglaciation this reorganization would leave some imprint on paleo productivity records here we present 230th normalized biogenic fluxes from an intermediate depth sediment core in the northwest pacific rc10 196 54 7 n 177 1 e 1007 m and place them within the context of a synthesis of previously published biogenic flux data from 49 deep sea cores north of 20 n ranging from 420 to 3968 m water depth the 230th normalized opal carbonate and organic carbon fluxes from rc10 196 peak approximately 13 000 calendar years bp during the bolling allerod b a period our data synthesis suggests that biogenic fluxes were in general lowest during the last glacial period increased somewhat in the northwest pacific during heinrich event 1 and reached a maximum across the entire north pacific during the b a period we evaluate several mechanisms as possible drivers of deglacial change in biogenic fluxes in the north pacific including changes in preservation sediment focusing sea ice extent iron inputs stratification and circulation shifts initiated in the north atlantic and north pacific our analysis suggests that while micronutrient sources likely contributed to some of the observed changes the heterogeneity in timing of glaciogenic retreat and sea level make these mechanisms unlikely causes of region wide contemporaneous peaks in export production we argue that paleoobservations are most consistent with ventilation increases in both the north pacific during h1 and north atlantic during b a being the primary drivers of increases in biogenic flux during the deglaciation as respectively they were likely to bring nutrients to the surface via increased vertical mixing and shoaling of the global thermocline