Juranek
Laurie W.
Juranek
Laurie W.
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ArticleSignificant biologically mediated CO2 uptake in the pacific arctic during the late open water season.(American Geophysical Union, 2019-01-10) Juranek, Laurie W. ; Takahashi, Taro ; Mathis, Jeremy T. ; Pickart, Robert S.Shifting baselines in the Arctic atmosphere‐sea ice‐ocean system have significant potential to alter biogeochemical cycling and ecosystem dynamics. In particular, the impact of increased open water duration on lower trophic level productivity and biological CO2 sequestration is poorly understood. Using high‐resolution observations of surface seawater dissolved O2/Ar and pCO2 collected in the Pacific Arctic in October 2011 and 2012, we evaluate spatial variability in biological metabolic status (autotrophy vs heterotrophy) as constrained by O2/Ar saturation (∆O2/Ar) as well as the relationship between net biological production and the sea‐air gradient of pCO2 (∆pCO2). We find a robust relationship between ∆pCO2 and ∆O2/Ar (correlation coefficient of −0.74 and −0.61 for 2011 and 2012, respectively), which suggests that biological production in the late open water season is an important determinant of the air‐sea CO2 gradient at a timeframe of maximal ocean uptake for CO2 in this region. Patchiness in biological production as indicated by ∆O2/Ar suggests spatially variable nutrient supply mechanisms supporting late season growth amidst a generally strongly stratified and nutrient‐limited condition.
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ArticleThe Atlantic Water boundary current in the Chukchi Borderland and Southern Canada Basin(American Geophysical Union, 2020-07-27) Li, Jianqiang ; Pickart, Robert S. ; Lin, Peigen ; Bahr, Frank B. ; Arrigo, Kevin R. ; Juranek, Laurie W. ; Yang, Xiao‐YiSynoptic shipboard measurements, together with historical hydrographic data and satellite data, are used to elucidate the detailed structure of the Atlantic Water (AW) boundary current system in the southern Canada Basin and its connection to the upstream source of AW in the Chukchi Borderland. Nine high‐resolution occupations of a transect extending from the Beaufort shelf to the deep basin near 152°W, taken between 2003 and 2018, reveal that there are two branches of the AW boundary current that flow beneath and counter to the Beaufort Gyre. Each branch corresponds to a warm temperature core and transports comparable amounts of Fram Strait Branch Water between roughly 200–700 m depth, although they are characterized by a different temperature/salinity (T/S) structure. The mean volume flux of the combined branches is 0.87 ± 0.13 Sv. Using the historical hydrographic data, the two branches are tracked upstream by their temperature cores and T/S signatures. This sheds new light on how the AW negotiates the Chukchi Borderland and why two branches emerge from this region. Lastly, the propagation of warm temperature anomalies through the region is quantified and shown to be consistent with the deduced circulation scheme.
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ArticleShort-term variability in euphotic zone biogeochemistry and primary productivity at Station ALOHA : a case study of summer 2012(John Wiley & Sons, 2015-08-13) Wilson, Samuel T. ; Barone, Benedetto ; Ascani, Francois ; Bidigare, Robert R. ; Church, Matthew J. ; del Valle, Daniela A. ; Dyhrman, Sonya T. ; Ferroon, Sara ; Fitzsimmons, Jessica N. ; Juranek, Laurie W. ; Kolber, Zbigniew S. ; Letelier, Ricardo M. ; Martinez-Garcia, Sandra ; Nicholson, David P. ; Richards, Kelvin J. ; Rii, Yoshimi M. ; Rouco, Monica ; Viviani, Donn A. ; White, Angelicque E. ; Zehr, Jonathan P. ; Karl, David M.Time-series observations are critical to understand the structure, function, and dynamics of marine ecosystems. The Hawaii Ocean Time-series program has maintained near-monthly sampling at Station ALOHA (22°45′N, 158°00′W) in the oligotrophic North Pacific Subtropical Gyre (NPSG) since 1988 and has identified ecosystem variability over seasonal to interannual timescales. To further extend the temporal resolution of these near-monthly time-series observations, an extensive field campaign was conducted during July–September 2012 at Station ALOHA with near-daily sampling of upper water-column biogeochemistry, phytoplankton abundance, and activity. The resulting data set provided biogeochemical measurements at high temporal resolution and documents two important events at Station ALOHA: (1) a prolonged period of low productivity when net community production in the mixed layer shifted to a net heterotrophic state and (2) detection of a distinct sea-surface salinity minimum feature which was prominent in the upper water column (0–50 m) for a period of approximately 30 days. The shipboard observations during July–September 2012 were supplemented with in situ measurements provided by Seagliders, profiling floats, and remote satellite observations that together revealed the extent of the low productivity and the sea-surface salinity minimum feature in the NPSG.
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ArticleStorm-induced upwelling of high pCO2 waters onto the continental shelf of the western Arctic Ocean and implications for carbonate mineral saturation states(American Geophysical Union, 2012-04-11) Mathis, Jeremy T. ; Pickart, Robert S. ; Byrne, Robert H. ; McNeil, Craig L. ; Moore, G. W. K. ; Juranek, Laurie W. ; Liu, Xuewu ; Ma, Jian ; Easley, Regina A. ; Elliot, Matthew M. ; Cross, Jessica N. ; Reisdorph, Stacey C. ; Bahr, Frank B. ; Morison, James H. ; Lichendorf, Trina ; Feely, Richard A.The carbon system of the western Arctic Ocean is undergoing a rapid transition as sea ice extent and thickness decline. These processes are dynamically forcing the region, with unknown consequences for CO2 fluxes and carbonate mineral saturation states, particularly in the coastal regions where sensitive ecosystems are already under threat from multiple stressors. In October 2011, persistent wind-driven upwelling occurred in open water along the continental shelf of the Beaufort Sea in the western Arctic Ocean. During this time, cold (<−1.2°C), salty (>32.4) halocline water—supersaturated with respect to atmospheric CO2 (pCO2 > 550 μatm) and undersaturated in aragonite (Ωaragonite < 1.0) was transported onto the Beaufort shelf. A single 10-day event led to the outgassing of 0.18–0.54 Tg-C and caused aragonite undersaturations throughout the water column over the shelf. If we assume a conservative estimate of four such upwelling events each year, then the annual flux to the atmosphere would be 0.72–2.16 Tg-C, which is approximately the total annual sink of CO2 in the Beaufort Sea from primary production. Although a natural process, these upwelling events have likely been exacerbated in recent years by declining sea ice cover and changing atmospheric conditions in the region, and could have significant impacts on regional carbon budgets. As sea ice retreat continues and storms increase in frequency and intensity, further outgassing events and the expansion of waters that are undersaturated in carbonate minerals over the shelf are probable.
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Working PaperReview of US GO-SHIP (Global Oceans Shipboard Hydrographic Investigations Program) An OCB and US CLIVAR Report(Woods Hole Oceanographic Institution, 2019-10) Bingham, Frederick ; Juranek, Laurie W. ; Mazloff, Matthew R. ; McKinley, Galen A. ; Nelson, Norman B. ; Wijffels, Susan E.The following document constitutes a review of the US GO-SHIP program, performed under the auspices of US Climate Variability and Predictability (CLIVAR) and Ocean Carbon Biogeochemistry (OCB) Programs. It is the product of an external review committee, charged and assembled by US CLIVAR and OCB with members who represent the interests of the programs and who are independent of US GO-SHIP support, which spent several months gathering input and drafting this report. The purpose of the review is to assess program planning, progress, and opportunities in collecting, providing, and synthesizing high quality hydrographic data to advance the scientific research goals of US CLIVAR and OCB.