277 research outputs found

    Telegram from Mesrob Ashjian, Reverend Archbishop of the Armenian Apostolic Church of America, to Geraldine Ferraro

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    Congratulatory telegram from Mesrob Ashjian, Reverend Archbishop of the Armenian Apostolic Church of America, to Geraldine Ferraro. Archbishop Ashjian calls Ferraro a sincere friend of the Armenian people. Includes standard response letter.https://ir.lawnet.fordham.edu/vice_presidential_campaign_correspondence_1984_new_york/1267/thumbnail.jp

    Pan-arctic depth distribution of diapausing Calanus copepods

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    Author Posting. © University of Chicago, 2019. This article is posted here by permission of University of Chicago for personal use, not for redistribution. The definitive version was published in Biological Bulletin 237(2), (2019): 76-89, doi: 10.1086/704694.Diapause at depth is considered an integral part of the life cycle of Calanus copepods, but few studies have focused on the Arctic species Calanus glacialis and Calanus hyperboreus. By analyzing a large set of pan-arctic observational data compiled from multiple sources, we show that Arctic Calanus has a broad depth distribution in winter, indicating that diapause at depth is a facultative strategy. Both species’ vertical distributions tend to deepen in winter and to be deeper and broader with increasing bottom depth, while individuals are aggregated closer to the sea floor in shallow areas. These results indicate that Arctic Calanus species pursue a relatively deep diapause habitat but are topographically blocked on the shelves. Interspecific differences in depth distribution during diapause suggest the importance of predation. The larger C. hyperboreus has a deeper diapause depth than C. glacialis, potentially to alleviate predation pressure or as a result of predation loss near the surface. Moreover, the mean depth of C. hyperboreus in winter is negatively associated with latitude, indicating a shoaling of the diapause population in the central Arctic Ocean where predation pressure is lower. Our results suggest a complex diapause behavior by Arctic Calanus, with implications for our view of the species’ roles in Arctic ecosystems.KØK was supported by the Woods Hole Oceanographic Institution John H. Steele Postdoctoral Scholar award and the VISTA Scholarship (http://www.vista.no). We are grateful to SigrĂșn JonasdĂłttir, Susan Mills, Imme Rutzen, Russ Hopcroft, Peter Munk, and Rasmus Swalethorp for kindly sharing observational data. We would like to thank two anonymous reviewers for insightful and constructive suggestions that helped us improve the manuscript.2020-09-1

    \u3ci\u3eAlexandrium\u3c/i\u3e in the Arctic: Are Harmful Algae Spreading as the Arctic Warms?

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    Alexandrium tamerense is a well-studied dinoflagellate known for its ability to produce the neurotoxin that causes paralytic shellfish poisoning. Until 1970 Alexandrium tamerense was only found in Europe, North America, and Japan but has been increasingly found all over the globe. Alexandrium is characteristically found in temperate and subtropical regions and as the Arctic warms, there is considerable concern that it may be expanding into the Arctic. We found Alexandrium tamerense during a research expedition to the Alaskan Beaufort Sea shelf to study upwelling. Upwelling events are known to support seasonal blooms of phytoplankton, which are important primary producers at the base of the oceanic food web. The Beaufort Sea in the Arctic Ocean is known to experience upwelling due to storms caused by atmospheric pressure differences between air masses over Canada and Alaska. This upwelling is becoming more frequent as sea ice melts and the Arctic becomes warmer. We examined the upwelling system in the Beaufort Sea during one of these storms, by collecting surface water samples before, during, and after an upwelling event. Here we present observations of Alexandrium tamarense, found before upwelling occurred, using three different methods.https://digitalcommons.odu.edu/gradposters2021_sciences/1012/thumbnail.jp

    Early ice retreat and ocean warming may induce copepod biogeographic boundary shifts in the Arctic Ocean

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    Author Posting. © American Geophysical Union, 2016. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 121 (2016): 6137-6158, doi:10.1002/2016JC011784.Early ice retreat and ocean warming are changing various facets of the Arctic marine ecosystem, including the biogeographic distribution of marine organisms. Here an endemic copepod species, Calanus glacialis, was used as a model organism, to understand how and why Arctic marine environmental changes may induce biogeographic boundary shifts. A copepod individual-based model was coupled to an ice-ocean-ecosystem model to simulate temperature- and food-dependent copepod life history development. Numerical experiments were conducted for two contrasting years: a relatively cold and normal sea ice year (2001) and a well-known warm year with early ice retreat (2007). Model results agreed with commonly known biogeographic distributions of C. glacialis, which is a shelf/slope species and cannot colonize the vast majority of the central Arctic basins. Individuals along the northern boundaries of this species' distribution were most susceptible to reproduction timing and early food availability (released sea ice algae). In the Beaufort, Chukchi, East Siberian, and Laptev Seas where severe ocean warming and loss of sea ice occurred in summer 2007, relatively early ice retreat, elevated ocean temperature (about 1–2°C higher than 2001), increased phytoplankton food, and prolonged growth season created favorable conditions for C. glacialis development and caused a remarkable poleward expansion of its distribution. From a pan-Arctic perspective, despite the great heterogeneity in the temperature and food regimes, common biogeographic zones were identified from model simulations, thus allowing a better characterization of habitats and prediction of potential future biogeographic boundary shifts.National Science Foundation Polar Programs Grant Number: (PLR-1417677, PLR-1417339, and PLR-1416920)2017-02-2

    Lingering Chukchi Sea sea ice and Chukchi Sea mean winds influence population age structure of euphausiids (krill) found in the bowhead whale feeding hotspot near Pt. Barrow, Alaska

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    © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Ashjian, C. J., Okkonen, S. R., Campbell, R. G., & Alatalo, P. Lingering Chukchi Sea sea ice and Chukchi Sea mean winds influence population age structure of euphausiids (krill) found in the bowhead whale feeding hotspot near Pt. Barrow, Alaska. Plos One, 16(7), (2021): e0254418, https://doi.org/10.1371/journal.pone.0254418.Interannual variability in euphausiid (krill) abundance and population structure and associations of those measures with environmental drivers were investigated in an 11-year study conducted in late August–early September 2005–2015 in offshelf waters (bottom depth > 40 m) in Barrow Canyon and the Beaufort Sea just downstream of Distributed Biological Observatory site 5 (DBO5) near Pt. Barrow, Alaska. Statistically-significant positive correlations were observed among krill population structure (proportion of juveniles and adults), the volume of Late Season Melt Water (LMW), and late-spring Chukchi Sea sea ice extent. High proportions of juvenile and adult krill were seen in years with larger volumes of LMW and greater spring sea ice extents (2006, 2009, 2012–2014) while the converse, high proportions of furcilia, were seen in years with smaller volumes of LMW and lower spring sea ice extent (2005, 2007, 2010, 2011, 2015). These different life stage, sea ice and water mass regimes represent integrated advective responses to mean fall and/or spring Chukchi Sea winds, driven by prevailing atmospheric pressure distributions in the two sets of years. In years with high proportions of juveniles and adults, late-spring and preceding-fall winds were weak and variable while in years with high proportions of furcilia, late-spring and preceding-fall winds were strong, easterly and consistent. The interaction of krill life history with yearly differences in the northward transports of krill and water masses along with sea ice retreat determines the population structure of late-summer krill populations in the DBO5 region near Pt. Barrow. Years with higher proportions of mature krill may provide larger prey to the Pt. Barrow area bowhead whale prey hotspot. The characteristics of prey near Pt. Barrow is dependent on krill abundance and size, large-scale environmental forcing, and interannual variability in recruitment success of krill in the Bering Sea.This research was supported by the National Science Foundation through grants PLR-1023331 (CJA), OPP-0436131 (CJA), PLR-1022139 (RGC), OPP-0436110 (RGC), PLR-1023446 (SRO), and OPP-043166 (SRO), the National Oceanic and Atmospheric Administration (NOAA) under cooperative agreement NA08OAR4320751 with the University of Alaska (SRO) and cooperative agreements NA17RJ1223 and NA09OAR4320129 with the Woods Hole Oceanographic Institution (CJA), the Bureau of Ocean Energy Management through Interagency Agreement 0106RU39923/M08PG20021 between the National Marine Fisheries Service and MMS/BOEM (CJA, RGC, SRO) and through the National Oceanographic Partnership Program award number N00014-08-1-0311 from the Office of Naval Research to the Woods Hole Oceanographic Institution (CJA, SRO, RGC). Additional support was provided by the Coastal Marine Institute at the University of Alaska (SRO, RGC) and the James M. and Ruth P. Clark Arctic Research Initiative Fund at the Woods Hole Oceanographic Institution (CJA). The participation of the K-12 teachers was supported by the National Science Foundation through the ARMADA program at the University of Rhode Island (2005, 2006) and through the POLARTrec program at the Arctic Research Consortium of the United States (2012)

    Biogeographic responses of the copepod Calanus glacialis to a changing Arctic marine environment

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    Author Posting. © The Author(s), 2017. This is the author's version of the work. It is posted here under a nonexclusive, irrevocable, paid-up, worldwide license granted to WHOI. It is made available for personal use, not for redistribution. The definitive version was published in Global Change Biology 24 (2018): e159-e170, doi:10.1111/gcb.13890.Dramatic changes have occurred in the Arctic Ocean over the past few decades, especially in terms of sea ice loss and ocean warming. Those environmental changes may modify the planktonic ecosystem with changes from lower to upper trophic levels. This study aimed to understand how the biogeographic distribution of a crucial endemic copepod species, Calanus glacialis, may respond to both abiotic (ocean temperature) and biotic (phytoplankton prey) drivers. A copepod individual-based model coupled to an ice-ocean-biogeochemical model was utilized to simulate temperature- and food-dependent life cycle development of C. glacialis annually from 1980 to 2014. Over the 35-year study period, the northern boundaries of modeled diapausing C. glacialis expanded poleward and the annual success rates of C. glacialis individuals attaining diapause in a circumpolar transition zone increased substantially. Those patterns could be explained by a lengthening growth season (during which time food is ample) and shortening critical development time (the period from the first feeding stage N3 to the diapausing stage C4). The biogeographic changes were further linked to large scale oceanic processes, particularly diminishing sea ice cover, upper ocean warming, and increasing and prolonging food availability, which could have potential consequences to the entire Arctic shelf/slope marine ecosystems.This study was funded by National Science Foundation Arctic System Science (ARCSS) Program (PLR-1417677, PLR-1417339, and PLR-1416920)

    Bowhead whale distribution and feeding near Barrow, Alaska, in late summer 2005–06

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    Author Posting. © Arctic Institute of North America, 2010. This article is posted here by permission of Arctic Institute of North America for personal use, not for redistribution. The definitive version was published in Arctic 63 (2010): 195-205.Aerial surveys for bowhead whales were conducted in conjunction with oceanographic sampling near Barrow, Alaska, in late summer of 2005 and 2006. In 2005, 145 whales were seen, mostly in two distinct aggregations: one (ca. 40 whales) in deep water in Barrow Canyon and the other (ca. 70 whales) in very shallow (< 10 m) water just seaward of the barrier islands. Feeding behaviours observed in the latter group included whales lying on their sides with mouths agape and groups of 5–10 whales swimming synchronously in turbid water. In 2006, 78 bowheads were seen, with ca. 40 whales feeding in dispersed groups of 3–11 whales. Feeding behaviours observed included surface skimming, echelon swimming, and synchronous diving and surfacing. Surfacing behaviour included head lunges by single animals and groups of 2–4 whales. Of 29 whales harvested at Barrow, 24 had been feeding. Euphausiids were the dominant prey in 2006 (10 of 13 stomachs), but not in 2005 (4 of 11 stomachs). Copepods were the dominant prey in the stomachs of three whales harvested near Barrow Canyon in 2005. Mysiids were the dominant prey in four stomachs, isopods in two, and amphipods in one although these taxa were not routinely captured during plankton sampling conducted in the weeks prior to the autumn harvest.Much of the field portion of this work was supported by the NSF/SNACS program

    The great 2012 Arctic Ocean summer cyclone enhanced biological productivity on the shelves

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    A coupled biophysical model is used to examine the impact of the great Arctic cyclone of early August 2012 on the marine planktonic ecosystem in the Pacific sector of the Arctic Ocean (PSA). Model results indicate that the cyclone influences the marine planktonic ecosystem by enhancing productivity on the shelves of the Chukchi, East Siberian, and Laptev seas during the storm. Although the cyclone\u27s passage in the PSA lasted only a few days, the simulated biological effects on the shelves last 1 month or longer. At some locations on the shelves, primary productivity (PP) increases by up to 90% and phytoplankton biomass by up to 40% in the wake of the cyclone. The increase in zooplankton biomass is up to 18% on 31 August and remains 10% on 15 September, more than 1 month after the storm. In the central PSA, however, model simulations indicate a decrease in PP and plankton biomass. The biological gain on the shelves and loss in the central PSA are linked to two factors. (1) The cyclone enhances mixing in the upper ocean, which increases nutrient availability in the surface waters of the shelves; enhanced mixing in the central PSA does not increase productivity because nutrients there are mostly depleted through summer draw down by the time of the cyclone\u27s passage. (2) The cyclone also induces divergence, resulting from the cyclone\u27s low‐pressure system that drives cyclonic sea ice and upper ocean circulation, which transports more plankton biomass onto the shelves from the central PSA. The simulated biological gain on the shelves is greater than the loss in the central PSA, and therefore, the production on average over the entire PSA is increased by the cyclone. Because the gain on the shelves is offset by the loss in the central PSA, the average increase over the entire PSA is moderate and lasts only about 10 days. The generally positive impact of cyclones on the marine ecosystem in the Arctic, particularly on the shelves, is likely to grow with increasing summer cyclone activity if the Arctic continues to warm and the ice cover continues to shrink

    The influence of sea ice and snow cover and nutrient availability on the formation of massive under-ice phytoplankton blooms in the Chukchi Sea

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    © The Author(s), 2015. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Deep Sea Research Part II: Topical Studies in Oceanography 118 (2015): 122-135, doi:10.1016/j.dsr2.2015.02.008.A coupled biophysical model is used to examine the impact of changes in sea ice and snow cover and nutrient availability on the formation of massive under-ice phytoplankton blooms (MUPBs) in the Chukchi Sea of the Arctic Ocean over the period 1988–2013. The model is able to reproduce the basic features of the ICESCAPE (Impacts of Climate on EcoSystems and Chemistry of the Arctic Pacific Environment) observed MUPB during July 2011. The simulated MUPBs occur every year during 1988–2013, mainly in between mid-June and mid-July. While the simulated under-ice blooms of moderate magnitude are widespread in the Chukchi Sea, MUPBs are less so. On average, the area fraction of MUPBs in the ice-covered areas of the Chukchi Sea during June and July is about 8%, which has been increasing at a rate of 2% yr–1 over 1988–2013. The simulated increase in the area fraction as well as primary productivity and chlorophyll a biomass is linked to an increase in light availability, in response to a decrease in sea ice and snow cover, and an increase in nutrient availability in the upper 100 m of the ocean, in conjunction with an intensification of ocean circulation. Simulated MUPBs are temporally sporadic and spatially patchy because of strong spatiotemporal variations of light and nutrient availability. However, as observed during ICESCAPE, there is a high likelihood that MUPBs may form at the shelf break, where the model simulates enhanced nutrient concentration that is seldom depleted between mid-June and mid-July because of generally robust shelf-break upwelling and other dynamic ocean processes. The occurrence of MUPBs at the shelf break is more frequent in the past decade than in the earlier period because of elevated light availability there. It may be even more frequent in the future if the sea ice and snow cover continues to decline such that light is more available at the shelf break to further boost the formation of MUPBs there.This work is supported by the NASA Cryosphere Program and Climate and Biological Response Program and the NSF Office of Polar Programs (Grant Nos. NNX12AB31G; NNX11AO91G; ARC-0901987)
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