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  • 1
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    Multiscale control of bacterial production by phytoplankton dynamics and sea ice along the western Antarctic Peninsula : a regional and decadal investigation (2012)
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © The Author(s), 2012. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Journal of Marine Systems 98-99 (2012): 26-39, doi:10.1016/j.jmarsys.2012.03.003.
    Description: We present results on phytoplankton and bacterial production and related hydrographic properties collected on nine annual summer cruises along the western Antarctic Peninsula. This region is strongly influenced by interannual variations in the duration and extent of sea ice cover, necessitating a decade-scale study. Our study area transitions from a nearshore region influenced by summer runoff from glaciers to an offshore, slope region dominated by the Antarctic Circumpolar Current. The summer bacterial assemblage is the product of seasonal warming and freshening following spring sea ice retreat and the plankton succession occurring in that evolving water mass. Bacterial production rates averaged 20 mgC m-2 d-1 and were a low (5%) fraction of the primary production (PP). There was significant variation in BP between regions and years, reflecting the variability in sea ice, Chlorophyll and PP. Leucine incorporation was significantly correlated (r2 ranging 0.2-0.7, p〈0.001) with both chlorophyll and PP across depths, regions and years indicating strong phytoplankton-bacteria coupling. Relationships with temperature were variable, including positive, negative and insignificant relationships (r2 〈0.2 for regressions with p〈0.05). Bacterial production is regulated indirectly by variations in sea ice cover within regions and over years, setting the levels of phytoplankton biomass accumulation and PP rates; these in turn fuel BP, to which PP is coupled via direct release from phytoplankton or other less direct pathways.
    Description: This research was supported by NSF Grants OPP-0217282 and 0823101 from the Antarctic Organisms and Ecosystems Program to HWD.
    Keywords: Bacteria ; Antarctica ; Bacterial production ; Primary production ; Sea ice
    Repository Name: Woods Hole Open Access Server
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  • 2
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    ASPIRE : the Amundsen Sea Polynya International Research Expedition (2012)
    The Oceanography Society
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © The Oceanography Society, 2012. This article is posted here by permission of The Oceanography Society for personal use, not for redistribution. The definitive version was published in Oceanography 25, no. 3 (2012): 40-53, doi:10.5670/oceanog.2012.73.
    Description: In search of an explanation for some of the greenest waters ever seen in coastal Antarctica and their possible link to some of the fastest melting glaciers and declining summer sea ice, the Amundsen Sea Polynya International Research Expedition (ASPIRE) challenged the capabilities of the US Antarctic Program and RVIB Nathaniel B. Palmer during Austral summer 2010–2011. We were well rewarded by both an extraordinary research platform and a truly remarkable oceanic setting. Here we provide further insights into the key questions that motivated our sampling approach during ASPIRE and present some preliminary findings, while highlighting the value of the Palmer for accomplishing complex, multifaceted oceanographic research in such a challenging environment.
    Description: This project was funded by the National Science Foundation Office of Polar Programs, Antarctic Organisms and Ecosystems (ANT-0839069 to PY, ANT-0838995 to RS, ANT-0838975 to SS, ANT-0838995 to OS, ANT- 0944727 to KA, and ANT-0839012 to Hugh Ducklow), and the Swedish Research Council (Grant 2008-6430 to SB and LR), with logistic support from the Swedish Polar Research Secretariat and Raytheon Polar Services.
    Repository Name: Woods Hole Open Access Server
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  • 3
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    Overview of the Arctic Sea state and boundary layer physics program (2019)
    American Geophysical Union
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    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2018. 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 123(12), (2018): 8674-8687, doi:10.1002/2018JC013766.
    Description: A large collaborative program has studied the coupled air‐ice‐ocean‐wave processes occurring in the Arctic during the autumn ice advance. The program included a field campaign in the western Arctic during the autumn of 2015, with in situ data collection and both aerial and satellite remote sensing. Many of the analyses have focused on using and improving forecast models. Summarizing and synthesizing the results from a series of separate papers, the overall view is of an Arctic shifting to a more seasonal system. The dramatic increase in open water extent and duration in the autumn means that large surface waves and significant surface heat fluxes are now common. When refreezing finally does occur, it is a highly variable process in space and time. Wind and wave events drive episodic advances and retreats of the ice edge, with associated variations in sea ice formation types (e.g., pancakes, nilas). This variability becomes imprinted on the winter ice cover, which in turn affects the melt season the following year.
    Description: This program was supported by the Office of Naval Research, Code 32, under Program Managers Scott Harper and Martin Jeffries. The crew of R/V Sikuliaq provide outstanding support in collecting the field data, and the US National Ice Center, German Aerospace Center (DLR), and European Space Agency facilitated the remote sensing collections and daily analysis products. RADARSAT‐2 Data and Products are from MacDonald, Dettwiler, and Associates Ltd., courtesy of the U.S. National Ice Center. Data, supporting information, and a cruise report can be found at http://www.apl.uw.edu/arcticseastate
    Keywords: Arctic ; waves ; autumn ; sea ice ; Beaufort ; flux
    Repository Name: Woods Hole Open Access Server
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  • 4
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    The disappearing cryosphere : impacts and ecosystem responses to rapid cryosphere loss (2012)
    American Institute of Biological Sciences
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Institute of Biological Sciences, 2012. This article is posted here by permission of American Institute of Biological Sciences for personal use, not for redistribution. The definitive version was published in BioScience 62 (2012): 405-415, doi:10.1525/bio.2012.62.4.11.
    Description: The cryosphere—the portion of the Earth's surface where water is in solid form for at least one month of the year—has been shrinking in response to climate warming. The extents of sea ice, snow, and glaciers, for example, have been decreasing. In response, the ecosystems within the cryosphere and those that depend on the cryosphere have been changing. We identify two principal aspects of ecosystem-level responses to cryosphere loss: (1) trophodynamic alterations resulting from the loss of habitat and species loss or replacement and (2) changes in the rates and mechanisms of biogeochemical storage and cycling of carbon and nutrients, caused by changes in physical forcings or ecological community functioning. These changes affect biota in positive or negative ways, depending on how they interact with the cryosphere. The important outcome, however, is the change and the response the human social system (infrastructure, food, water, recreation) will have to that change.
    Description: The authors wish to thank the funding provided by the National Science Foundation’s (NSF) Long Term Ecological Research (LTER) Network for supporting our long-term studies, in which we track the ecosystem response to the disappearing cryosphere. NSF LTER Site Grants OPP 0823101, OPP 1115245, DEB 1114804, DEB-1026415, DEB-0620579, and DEB-1027341 supported the authors during the preparation of this article.
    Description: 2012-10-01
    Keywords: Cryosphere ; Ecosystem response ; Environmental observatories
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  • 5
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    Antarctic sea ice—A polar opposite? (2012)
    The Oceanography Society
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    Publication Date: 2022-05-25
    Description: Author Posting. © The Oceanography Society, 2012. This article is posted here by permission of The Oceanography Society for personal use, not for redistribution. The definitive version was published in Oceanography 25, no. 3 (2012): 140-151, doi:10.5670/oceanog.2012.88.
    Description: As the world's ice diminishes in the face of climate change—from the dramatic decline in Arctic sea ice, to thinning at the margins of both the Greenland and Antarctic ice sheets, to retreating mountain glaciers the world over—Antarctic sea ice presents something of a paradox. The trend in total sea ice extent in the Antarctic has remained steady, or even increased slightly, over the past three decades, confounding climate model predictions showing moderate to strong declines. This apparent intransigence masks dramatic regional trends; declines in sea ice in the Bellingshausen Sea region that rival the high-profile decline in the Arctic have been matched by opposing increases in the Ross Sea. Much of the explanation lies in the unique nature of the Antarctic sea ice zone. Its position surrounding the continent and exposure to the high-energy wind and wave fields of the open Southern Ocean shape both its properties and its connection to the atmosphere and ocean in ways very different from the Arctic. Sea ice extent and variability are strongly driven by large-scale climate variability patterns such as the El Niño-Southern Oscillation and the Southern Annular Mode. Because many of these patterns have opposing effects in different regions around the continent, decreases in one region are often accompanied by similar, opposing increases in another. Yet, the failure of climate models to capture either the overall or regional behavior also reflects, in part, a poor understanding of sea ice processes. Considerable insight has been gained into the nature of these processes over the past several decades through field expeditions aboard icebreakers. However, much remains to be discovered about the nature of Antarctic sea ice; its connections with the ocean, atmosphere, and ecosystem; and its complex response to present and future climate change.
    Description: Rob Massom was supported by the Australian Government’s Cooperative Research Centre programme through the ACE CRC, and this work contributes to AAS Projects 3024 and 4116 and AAD CPC Project 18.
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  • 6
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    West Antarctic Peninsula : an ice-dependent coastal marine ecosystem in transition (2013)
    The Oceanography Society
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © The Oceanography Society, 2013. This article is posted here by permission of The Oceanography Society] for personal use, not for redistribution. The definitive version was published in Oceanography 26, no. 3 (2013): 190–203, doi:10.5670/oceanog.2013.62.
    Description: The extent, duration, and seasonality of sea ice and glacial discharge strongly influence Antarctic marine ecosystems. Most organisms' life cycles in this region are attuned to ice seasonality. The annual retreat and melting of sea ice in the austral spring stratifies the upper ocean, triggering large phytoplankton blooms. The magnitude of the blooms is proportional to the winter extent of ice cover, which can act as a barrier to wind mixing. Antarctic krill, one of the most abundant metazoan populations on Earth, consume phytoplankton blooms dominated by large diatoms. Krill, in turn, support a large biomass of predators, including penguins, seals, and whales. Human activity has altered even these remote ecosystems. The western Antarctic Peninsula region has warmed by 7°C over the past 50 years, and sea ice duration has declined by almost 100 days since 1978, causing a decrease in phytoplankton productivity in the northern peninsula region. Besides climate change, Antarctic marine systems have been greatly altered by harvesting of the great whales and now krill. It is unclear to what extent the ecosystems we observe today differ from the pristine state.
    Description: Palmer LTER is supported by National Science Foundation grant ANT-0823101. Amsler was supported by NSF ANT- 0838773 and ANT-1041022. RaTS is a component of the Polar Oceans research program, funded by the British Antarctic Survey.
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  • 7
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    Penguin biogeography along the West Antarctic Peninsula : testing the canyon hypothesis with Palmer LTER observations (2013)
    The Oceanography Society
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © The Oceanography Society, 2013. This article is posted here by permission of The Oceanography Society for personal use, not for redistribution. The definitive version was published in Oceanography 26, no. 3 (2013): 204–206, doi:10.5670/oceanog.2013.63.
    Description: The West Antarctic Peninsula (WAP) is home to large breeding colonies of the ice-dependent Antarctic Adélie penguin (Pygoscelis adeliae). Although the entire inner continental shelf is highly productive, with abundant phytoplankton and krill populations, penguin colonies are distributed heterogeneously along the WAP. This ecological conundrum targets a long-standing question of interest: what environmental factors structure the locations of Adélie penguin "hot spots" throughout the WAP?
    Description: Palmer LTER is supported by NSF grant OPP-0823101 and the Gordon and Betty Moore Foundation (1859).
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  • 8
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    Stable Isotope clues to the formation and evolution of refrozen melt ponds on Arctic Sea ice. (2019)
    American Geophysical Union
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    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2018. 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 123(12), (2018): 8887-8901, doi:10.1029/2018JC013797.
    Description: Sea ice is one of the determining parameters of the climate system. The presence of melt ponds on the surface of Arctic sea ice plays a critical role in the mass balance of sea ice. A total of nine cores was collected from multiyear ice refrozen melt ponds and adjacent hummocks during the 2015 Arctic Sea State research cruise. The depth profiles of water isotopes, salinity, and ice texture for these sea ice cores were examined to provide information about the development of refrozen melt ponds and water balance generation processes, which are otherwise difficult to acquire. The presence of meteoric water with low oxygen isotope values as relatively thin layers indicates melt pond water stability and little mixing during formation and refreezing. The hydrochemical characteristics of refrozen melt pond and seawater depth profiles indicate little snowmelt enters the upper ocean during melt pond refreezing. Due to the seasonal characters of deuterium excess for Arctic precipitation, water balance calculations utilizing two isotopic tracers (oxygen isotope and deuterium excess) suggest that besides the melt of snow cover, the precipitation input in the melt season may also play a role in the evolution of melt ponds. The dual‐isotope mixing model developed here may become more valuable in a future scenario of increasing Arctic precipitation. The layers of meteoric origin were found at different depths in the refrozen melt pond ice cores. Surface topography information collected at several core sites was examined for possible explanations of different structures of refrozen melt ponds.
    Description: The coauthors (S. F. A., S. S., T. M., and B. W.) wish to thank the other DRI participants and the Captain and crew of the Sikuliaq's October 2015 cruise for their assistance in the sample collections analyzed in the paper. Jim Thomson (Chief Scientist), Scott Harper (ONR Program Manager), and Martin Jeffries (ONR Program Manager) are particularly acknowledged for their unwavering assistance and leadership during the 5 years of the SeaState DRI. We thank Guy Williams for production of the aerial photo mosaic. Funding from the Office of Naval Research N00014‐13‐1‐0435 (S. F. A. and B. W.), N00014‐13‐1‐0434 (S. S.), and N00014‐13‐1‐0446 (T. M.) supported this research through grants to UTSA, UColorado, and WHOI, respectively. This project was also funded (in part) by the University of Texas at San Antonio, Office of the Vice President for Research (Y. G. and S. F. A.). Data for the stable isotope mixing models used in this study are shown in supporting information Tables S1–S3.
    Description: 2019-05-15
    Keywords: Arctic ; sea ice ; isotope tracer ; melt pond ; oxygen isotope ; deuterium excess
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  • 9
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    Particle export from the upper ocean over the continental shelf of the west Antarctic Peninsula: A long-term record, 1992–2007 (2008)
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    Publication Date: 2022-05-26
    Description: Author Posting. © The Author(s), 2008. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Deep Sea Research Part II: Topical Studies in Oceanography 55 (2008): 2118-2131, doi:10.1016/j.dsr2.2008.04.028.
    Description: Includes supplemental materials
    Description: We report on results of a long-term (1993-2007) time series sediment trap moored at 170 m to the west of the Antarctic Peninsula in the mid-continental shelf region (350 m depth; 64º30’ S, 66º00’ W). This is a region characterized by late spring-summer diatom blooms, moderately high seasonal primary productivity (50-150 mmol C m-2 d-1 in December-February) and high phytoplankton and krill biomass in the seasonal sea ice zone. The mass flux ranged from near 0 to over 1 g m-2 d-1 and was near 0 to 〉30% organic carbon (mean 8%). Sedimentation from the upper ocean as estimated by the trap collections at 170 m exhibited strong seasonality with high fluxes (1-10 mmol C m-2 d-1) in November-March following ice retreat and very low fluxes (〈0.001 mmol C m-2 d-1) during the Austral winter and under sea ice cover. An average of 85% of the annual export of 212 mmol C m-2 occurred during the seasonal peak flux episodes. Over the trap record, the annual peak flux episode has tended to occur later in the Austral summer, advancing by about 40 days since 1993. The time-integrated sedimentation during the peak flux episode was 〈1 – 50% of the SeaWiFS-estimated primary production (mean 4%) at the trap site over the period 1998-2006. The elemental composition of material captured in the traps had an average C:N:P of 212:28:1, greater than the canonical Redfield values. High C:P ratios (400- 600) corresponded with the annual flux peak, indicating preferential loss of P from the sinking particles in the summer, ice-free period. The composition of the exported material more closely approximated the Redfield composition during the low-flux, winter period.
    Description: This research was supported by NSF Grants OPP 9011927, 9632763 and 0217282 for the Palmer Long Term Ecological Research project.
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  • 10
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    Effect of continental shelf canyons on phytoplankton biomass and community composition along the western Antarctic Peninsula (2015)
    Inter-Research
    Details
    Publication Date: 2022-05-26
    Description: © The Author(s), 2015. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Marine Ecology Progress Series 524 (2015): 11-26, doi:10.3354/meps11189.
    Description: The western Antarctic Peninsula is experiencing dramatic climate change as warm, wet conditions expand poleward and interact with local physics and topography, causing differential regional effects on the marine ecosystem. At local scales, deep troughs (or canyons) bisect the continental shelf and act as conduits for warm Upper Circumpolar Deep Water, with reduced seasonal sea ice coverage, and provide a reservoir of macro- and micronutrients. Shoreward of many canyon heads are Adélie penguin breeding colonies; it is hypothesized that these locations reflect improved or more predictable access to higher biological productivity overlying the canyons. To synoptically assess the potential impacts of regional bathymetry on the marine ecosystem, 4 major canyons were identified along a latitudinal gradient west of the Antarctic Peninsula using a high-resolution bathymetric database. Biological-physical dynamics above and adjacent to canyons were compared using in situ pigments and satellite-derived sea surface temperature, sea ice and ocean color variables, including chlorophyll a (chl a) and fucoxanthin derived semi-empirically from remote sensing reflectance. Canyons exhibited higher sea surface temperature and reduced sea ice coverage relative to adjacent shelf areas. In situ and satellite-derived pigment patterns indicated increased total phytoplankton and diatom biomass over the canyons (by up to 22 and 35%, respectively), as well as increases in diatom relative abundance (fucoxanthin:chl a). While regional heterogeneity is apparent, canyons appear to support a phytoplankton community that is conducive to both grazing by krill and enhanced vertical export, although it cannot compensate for decreased biomass and diatom relative abundance during low sea ice conditions.
    Description: We acknowledge support from the National Aeronautics and Space Administration Ocean Bio - logy and Biogeochemistry Program (NNX14AL86G) and the National Science Foundation Polar Programs awards 0823101 (Antarctic Organisms and Ecosystems Program) and 1440435 (Antarctic Integrated System Science) to the Palmer LTER program.
    Keywords: Western Antarctic Peninsula ; Canyons ; Phytoplankton ; Diatoms ; Remote sensing ; Adélie penguin habitat ; Sea ice
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