Laney Samuel R.

No Thumbnail Available
Last Name
First Name
Samuel R.

Search Results

Now showing 1 - 14 of 14
  • Article
    Sea surface pCO2 and O2 dynamics in the partially ice-covered Arctic Ocean
    (John Wiley & Sons, 2017-02-25) Islam, Fakhrul ; DeGrandpre, Michael D. ; Beatty, Cory ; Timmermans, Mary-Louise ; Krishfield, Richard A. ; Toole, John M. ; Laney, Samuel R.
    Understanding the physical and biogeochemical processes that control CO2 and dissolved oxygen (DO) dynamics in the Arctic Ocean (AO) is crucial for predicting future air-sea CO2 fluxes and ocean acidification. Past studies have primarily been conducted on the AO continental shelves during low-ice periods and we lack information on gas dynamics in the deep AO basins where ice typically inhibits contact with the atmosphere. To study these gas dynamics, in situ time-series data have been collected in the Canada Basin during late summer to autumn of 2012. Partial pressure of CO2 (pCO2), DO concentration, temperature, salinity, and chlorophyll-a fluorescence (Chl-a) were measured in the upper ocean in a range of sea ice states by two drifting instrument systems. Although the two systems were on average only 222 km apart, they experienced considerably different ice cover and external forcings during the 40–50 day periods when data were collected. The pCO2 levels at both locations were well below atmospheric saturation whereas DO was almost always slightly supersaturated. Modeling results suggest that air-sea gas exchange, net community production (NCP), and horizontal gradients were the main sources of pCO2 and DO variability in the sparsely ice-covered AO. In areas more densely covered by sea ice, horizontal gradients were the dominant source of variability, with no significant NCP in the surface mixed layer. If the AO reaches equilibrium with atmospheric CO2 as ice cover continues to decrease, aragonite saturation will drop from a present mean of 1.00 ± 0.02 to 0.86 ± 0.01.
  • Article
    Insights into water mass origins in the central Arctic Ocean from in-situ dissolved organic matter fluorescence
    (American Geophysical Union, 2021-06-27) Stedmon, Colin ; Amon, Rainer M. W. ; Bauch, Dorothea ; Bracher, Astrid ; Gonçalves-Araujo, Rafael ; Hoppmann, Mario ; Krishfield, Richard A. ; Laney, Samuel R. ; Rabe, Benjamin ; Reader, Heather ; Granskog, Mats A.
    The Arctic Ocean receives a large supply of dissolved organic matter (DOM) from its catchment and shelf sediments, which can be traced across much of the basin's upper waters. This signature can potentially be used as a tracer. On the shelf, the combination of river discharge and sea-ice formation, modifies water densities and mixing considerably. These waters are a source of the halocline layer that covers much of the Arctic Ocean, but also contain elevated levels of DOM. Here we demonstrate how this can be used as a supplementary tracer and contribute to evaluating ocean circulation in the Arctic. A fraction of the organic compounds that DOM consists of fluoresce and can be measured using in-situ fluorometers. When deployed on autonomous platforms these provide high temporal and spatial resolution measurements over long periods. The results of an analysis of data derived from several Ice Tethered Profilers (ITPs) offer a unique spatial coverage of the distribution of DOM in the surface 800 m below Arctic sea-ice. Water mass analysis using temperature, salinity and DOM fluorescence, can clearly distinguish between the contribution of Siberian terrestrial DOM and marine DOM from the Chukchi shelf to the waters of the halocline. The findings offer a new approach to trace the distribution of Pacific waters and its export from the Arctic Ocean. Our results indicate the potential to extend the approach to separate freshwater contributions from, sea-ice melt, riverine discharge and the Pacific Ocean.
  • Article
    The euphotic zone under Arctic Ocean sea ice : vertical extents and seasonal trends
    (John Wiley & Sons, 2017-03-26) Laney, Samuel R. ; Krishfield, Richard A. ; Toole, John M.
    Eight Ice-Tethered Profilers were deployed in the Arctic Ocean between 2011 and 2013 to measure vertical distributions of photosynthetically active radiation (PAR) and other bio-optical properties in ice-covered water columns, multiple times a day over periods of up to a year. With the radiometers used on these profilers, PAR could be measured to depths of only ∼20–40 m in the central Arctic in late summer under sea ice ∼1 m thick. At lower latitudes in the Beaufort Gyre, late summer PAR was measurable under ice to depths exceeding 125 m. The maximum depths of measurable PAR followed seasonal trends in insolation, with isolumes shoaling in the fall as solar elevation decreased and deepening in spring and early summer after insolation resumed and sea ice diminished. PAR intensities were often anomalously low above 20 m, likely due to a shading effect associated with local horizontal heterogeneity in light transmittance by the overlying sea ice. A model was developed to parameterize these complex vertical PAR distributions to improve estimates of the water column diffuse attenuation coefficient and other related parameters. Such a model is necessary to separate the effect of surface ice heterogeneity on under-ice PAR profiles from that of the water column itself, so that euphotic zone depth in ice-covered water columns can be computed using canonical metrics such as the 1% light level. Water column diffuse attenuation coefficients derived from such autonomously-collected PAR profile data, using this model, agreed favorably with values determined manually in complementary studies.
  • Article
    Ice-tethered profiler measurements of dissolved oxygen under permanent ice cover in the Arctic Ocean
    (American Meteorological Society, 2010-11) Timmermans, Mary-Louise ; Krishfield, Richard A. ; Laney, Samuel R. ; Toole, John M.
    Four ice-tethered profilers (ITPs), deployed between 2006 and 2009, have provided year-round dissolved oxygen (DO) measurements from the surface mixed layer to 760-m depth under the permanent sea ice cover in the Arctic Ocean. These ITPs drifted with the permanent ice pack and returned 2 one-way profiles per day of temperature, salinity, and DO. Long-term calibration drift of the oxygen sensor can be characterized and removed by referencing to recently calibrated ship DO observations on deep isotherms. Observed changes in the water column time series are due to both drift of the ITP into different water masses and seasonal variability, driven by both physical and biological processes within the water column. Several scientific examples are highlighted that demonstrate the considerable potential for sustained ITP-based DO measurements to better understand the Arctic Ocean circulation patterns and biogeochemical processes beneath the sea ice.
  • Article
    Penetrative radiative flux in the Bay of Bengal
    (The Oceanography Society, 2016-06) Lotliker, Aneesh ; Omand, Melissa M. ; Lucas, Andrew J. ; Laney, Samuel R. ; Mahadevan, Amala ; Ravichandran, M.
    The Bay of Bengal (BoB), a semi-enclosed basin in the northern Indian Ocean, is a complex region with large freshwater inputs and strong vertical stratification that result in a shallow, spatially variable mixed layer. With the exception of shortwave insolation, the air-sea heat exchange occurs at the sea surface and is vertically redistributed by mixing and advection. Strongly stratified, shallow mixed layers inhibit vertical mixing, and the penetration of solar radiation through the base of the mixed layer can lead to redistribution of upper-ocean heat. This paper compiles observations of hyperspectral downwelling irradiance (Ed) from 67 profiles collected during six research cruises in the BoB that span a broad range of regions and seasons between 2009 and 2014. We report attenuation length scales computed using double and single exponential models and quantify the penetration of radiative flux below the mixed layer depth (Qpen). We then evaluate estimates of Qpen obtained from published chlorophyll-based models and compare them to our observations. We find that the largest penetrative heat flux (up to 40% of the incident Ed) occurs near 16°N where the mixed layers are shallow and the water is optically clear.
  • Article
    The seeding of ice algal blooms in Arctic pack ice : the multiyear ice seed repository hypothesis
    (John Wiley & Sons, 2017-07-03) Olsen, Lasse M. ; Laney, Samuel R. ; Duarte, Pedro ; Kauko, Hanna Maria ; Fernández-Méndez, Mar ; Mundy, Christopher J. ; Rösel, Anja ; Meyer, Amelie ; Itkin, Polona ; Cohen, Lana ; Peeken, Ilka ; Tatarek, Agnieszka ; Róźańska-Pluta, Magdalena ; Wiktor, Jozef ; Taskjelle, Torbjørn ; Pavlov, Alexey K. ; Hudson, Stephen R. ; Granskog, Mats A. ; Hop, Haakon ; Assmy, Philipp
    During the Norwegian young sea ICE expedition (N-ICE2015) from January to June 2015 the pack ice in the Arctic Ocean north of Svalbard was studied during four drifts between 83° and 80°N. This pack ice consisted of a mix of second year, first year, and young ice. The physical properties and ice algal community composition was investigated in the three different ice types during the winter-spring-summer transition. Our results indicate that algae remaining in sea ice that survived the summer melt season are subsequently trapped in the upper layers of the ice column during winter and may function as an algal seed repository. Once the connectivity in the entire ice column is established, as a result of temperature-driven increase in ice porosity during spring, algae in the upper parts of the ice are able to migrate toward the bottom and initiate the ice algal spring bloom. Furthermore, this algal repository might seed the bloom in younger ice formed in adjacent leads. This mechanism was studied in detail for the dominant ice diatom Nitzschia frigida. The proposed seeding mechanism may be compromised due to the disappearance of older ice in the anticipated regime shift toward a seasonally ice-free Arctic Ocean.
  • Article
    Optical, structural and kinematic characteristics of freshwater plumes under landfast sea ice during the spring freshet in the Alaskan coastal Arctic
    (American Geophysical Union, 2021-11-25) Okkonen, Stephen R. ; Laney, Samuel R.
    Rivers deliver freshwater and entrained terrestrial materials into the coastal ocean from adjacent continental landmasses. In the coastal Arctic, a large fraction of terrestrially sourced dissolved and particulate organic carbon (DOC and POC) is delivered by snowpack meltwaters of the spring freshet, when many coastal ocean regions remain covered by landfast ice. Here we report on an array of moored sensors and telemetering ice buoys deployed in advance of the 2018 spring freshet in Stefansson Sound near Prudhoe Bay, Alaska. This instrumented array monitored temporal and spatial variations in hydrographic properties before and during the freshet, as well as optical properties that serve as proxies for DOC and POC contained in the freshet plumes. The temporal evolution of these optical signals occurred in five stages, each associated with characteristic water column structural and kinematic characteristics. Spatial differences among fluorescent dissolved organic matter (FDOM) and optical backscatter (OBS) signals across the ice buoy array, evident later during the freshet, allowed identification of plume waters sourced from the Kuparuk, Sagavanirktok, and Shaviovik drainage basins.
  • Article
    Diatoms favor their younger daughters
    (Association for the Sciences of Limnology and Oceanography, 2012-09) Laney, Samuel R. ; Olson, Robert J. ; Sosik, Heidi M.
    We used a time-lapse imaging approach to examine cell division in the marine centric diatom Ditylum brightwellii and observed that daughter cells who inherited their parents' hypothecal frustule half were more likely to divide before their sisters. This is consistent with observations in Escherichia coli of a bias between sister cells, where faster growth in one sister is thought to arise from its inheriting parental material with less oxidative damage. We also observed that hypothecal sisters in D. brightwellii were more likely to inherit a greater proportion of their parents' cellular material, similar to what has been seen in E. coli. We found a statistically significant correlation between the amount of parental material inherited by a hypothecal daughter and its relative division rate, indicating that this extra material inherited by the hypothecal daughter plays a role in its more rapid division. Furthermore, the intercept in this regression was greater than zero, indicating that other factors, such as differences in the quality of inherited material, also play a role. This similarity between two taxonomically distant microbes suggests that favoritism toward one daughter might occur broadly among unicellular organisms that reproduce asexually by binary fission. Such a bias in cell division might be advantageous, given model predictions that show that favoring one daughter at the expense of the other can result in higher population growth rates, increasing the chance that a cell's genotype will survive compared to a model where the daughters divide at equal rates.
  • Article
    Leads in Arctic pack ice enable early phytoplankton blooms below snow-covered sea ice
    (Nature Publishig Group, 2019-01-17) Assmy, Philipp ; Fernández-Méndez, Mar ; Duarte, Pedro ; Meyer, Amelie ; Randelhoff, Achim ; Mundy, Christopher J. ; Olsen, Lasse M. ; Kauko, Hanna Maria ; Bailey, Allison ; Chierici, Melissa ; Cohen, Lana ; Doulgeris, Anthony P. ; Ehn, Jens K. ; Fransson, Agneta ; Gerland, Sebastian ; Hop, Haakon ; Hudson, Stephen R. ; Hughes, Nick ; Itkin, Polona ; Johnsen, Geir ; King, Jennifer A. ; Koch, Boris P. ; Koenig, Zoe ; Kwasniewski, Slawomir ; Laney, Samuel R. ; Nicolaus, Marcel ; Pavlov, Alexey K. ; Polashenski, Christopher M. ; Provost, Christine ; Rösel, Anja ; Sandbu, Marthe ; Spreen, Gunnar ; Smedsrud, Lars H. ; Sundfjord, Arild ; Taskjelle, Torbjørn ; Tatarek, Agnieszka ; Wiktor, Jozef ; Wagner, Penelope M. ; Wold, Anette ; Steen, Harald ; Granskog, Mats A.
    The Arctic icescape is rapidly transforming from a thicker multiyear ice cover to a thinner and largely seasonal first-year ice cover with significant consequences for Arctic primary production. One critical challenge is to understand how productivity will change within the next decades. Recent studies have reported extensive phytoplankton blooms beneath ponded sea ice during summer, indicating that satellite-based Arctic annual primary production estimates may be significantly underestimated. Here we present a unique time-series of a phytoplankton spring bloom observed beneath snow-covered Arctic pack ice. The bloom, dominated by the haptophyte algae Phaeocystis pouchetii, caused near depletion of the surface nitrate inventory and a decline in dissolved inorganic carbon by 16 ± 6 g C m−2. Ocean circulation characteristics in the area indicated that the bloom developed in situ despite the snow-covered sea ice. Leads in the dynamic ice cover provided added sunlight necessary to initiate and sustain the bloom. Phytoplankton blooms beneath snow-covered ice might become more common and widespread in the future Arctic Ocean with frequent lead formation due to thinner and more dynamic sea ice despite projected increases in high-Arctic snowfall. This could alter productivity, marine food webs and carbon sequestration in the Arctic Ocean.
  • Article
    An autonomous buoy system for observing spring freshet plumes under landfast sea ice
    (Association for the Sciences of Limnology and Oceanography, 2021-11-30) Laney, Samuel R. ; Okkonen, Stephen R.
    An ice buoy system was developed to measure oceanographic properties of freshwater plumes that occur in Arctic coastal oceans under landfast sea ice during the spring freshet. By implanting such systems into sea ice weeks or months in advance of the freshet event, sensors can be located immediately underneath the sea ice layer in situ at depths that riverine freshwater will occupy later when the freshet arrives. This observing approach is modular, can accommodate a wide range of sensors, is designed intentionally for use in remote regions, and can be readily deployed in any nearshore region that can be accessed by snowmachine. The buoy system incorporates an integral floatation collar that allows it to continue sampling as the coastal ocean becomes progressively ice free in the months after the freshet event. Automated sampling and telemetry via a satellite data network provide near-real-time observations of the timing and character of under-ice freshet plumes. An assessment study was done with an array of these ice buoy systems, outfitted with basic hydrographic and optical sensors and deployed in advance of the 2018 and 2019 freshets in landfast sea ice near the mouths of three coastal rivers in Stefansson Sound, Alaska.
  • Article
    Nitrogen limitation of the summer phytoplankton and heterotrophic prokaryote communities in the Chukchi Sea
    (Frontiers Media, 2018-10-15) Mills, Matthew M. ; Brown, Zachary W. ; Laney, Samuel R. ; Ortega-Retuerta, Eva ; Lowry, Kate E. ; van Dijken, Gert L. ; Arrigo, Kevin R.
    Major changes to Arctic marine ecosystems have resulted in longer growing seasons with increased phytoplankton production over larger areas. In the Chukchi Sea, the high productivity fuels intense benthic denitrification creating a nitrogen (N) deficit that is transported through the Arctic to the Atlantic Ocean, where it likely fuels N fixation. Given the rapid pace of environmental change and the potentially globally significant N deficit, we conducted experiments aimed at understanding phytoplankton and microbial N utilization in the Chukchi Sea. Ship-board experiments tested the effect of nitrate (NO3-) additions on both phytoplankton and heterotrophic prokaryote abundance, community composition, photophysiology, carbon fixation and NO3- uptake rates. Results support the critical role of NO3- in limiting summer phytoplankton communities to small cells with low production rates. NO3- additions increased particulate concentrations, abundance of large diatoms, and rates of carbon fixation and NO3- uptake by cells >1 μm. Increases in the quantum yield and electron turnover rate of photosystem II in +NO3- treatments suggested that phytoplankton in the ambient dissolved N environment were N starved and unable to build new, or repair damaged, reaction centers. While some increases in heterotrophic prokaryote abundance and production were noted with NO3- amendments, phytoplankton competition or grazers likely dampened these responses. Trends toward a warmer more stratified Chukchi Sea will likely enhance summer oligotrophic conditions and further N starve Chukchi Sea phytoplankton communities.
  • Article
    A general-purpose microcontroller-based framework for integrating oceanographic sensors, instruments, and peripherals
    (American Meteorological Society, 2017-02-15) Laney, Samuel R.
    Sensors and instruments for basic oceanographic properties are becoming increasingly sophisticated, which both simplifies and complicates their use in field studies. This increased sophistication disproportionately affects smaller-scale observational efforts that are less likely to be well supported technically but which need to integrate instruments, sensors, and commonly needed peripheral devices in ways not envisioned by their manufacturers. A general-purpose hardware and software framework was developed around a widely used family of low-power microcontrollers to lessen the technical expertise and customization required to integrate sensors, instruments, and peripherals, and thus simplify such integration scenarios. Both the hardware and associated firmware development tools provide a range of features often required in such scenarios: serial data interfaces, analog inputs and outputs, logic lines and power-switching capability, nonvolatile storage of data and parameters for sampling or configuration, and serial communication interfaces to supervisory or telemetry systems. The microcontroller and additional components needed to implement this integration framework are small enough to encapsulate in standard cable splices, creating a small form factor “smart cable” that can be readily wired and programmed for a range of integration needs. An application programming library developed for this hardware provides skeleton code for functions commonly desired when integrating sensors, instruments, and peripherals. This minimizes the firmware programming expertise needed to apply this framework in many integration scenarios and thus streamlines the development of firmware for different field applications. Envisioned applications are in field programs where significant technical instrumentation expertise is unavailable or not cost effective.
  • Article
    A fiber optic spectrometry system for measuring irradiance distributions in sea ice environments
    (American Meteorological Society, 2014-12) Wang, Hangzhou ; Chen, Ying ; Song, Hong ; Laney, Samuel R.
    A fiber optic–based spectrometry system was developed to enable automated, long-term measurements of spectral irradiance in sea ice environments. This system utilizes a single spectrometer module that measures the irradiance transmitted by multiple optical fibers, each coupled to the input fiber of the module via a mechanical rotary multiplexer. Small custom-printed optical diffusers, fixed to the input end of each fiber, allow these probes to be frozen into ice auger holes as small as 5 cm in diameter. Temperature-dependent biases in the spectrometer module and associated electronics were examined down to −40°C using an environmental chamber to identify any artifacts that might arise when operating these electronic and optical components below their vendor-defined lower temperature limits. The optical performance of the entire system was assessed by freezing multiple fiber probes in a 1.2-m-tall ice column, illuminating from above with a light source, and measuring spectral irradiance distributions at different depths within the ice column. Results indicated that the radiometric sensitivity of this fiber-based system is comparable to that of commercially available oceanographic spectroradiometers.
  • Article
    Optical insight into riverine influences on dissolved and particulate organic carbon in a coastal arctic lagoon system
    (American Geophysical Union, 2023-04-04) Catipovic, Luka ; Longnecker, Krista ; Okkonen, Stephen R. ; Koestner, Daniel ; Laney, Samuel R.
    Arctic coastal margins receive organic material input from rivers, melted sea ice, and coastal erosion, phenomena that are all undergoing changes related to global climate. The optical properties of coastal Arctic waters contain information on this organic material, and we examined three optical properties of seawater (absorption, backscatter, and fluorescence) for their relationships to variability in dissolved and particulate organic carbon (DOC and POC) in Stefansson Sound, Alaska, a coastal Arctic embayment. During open water periods in 2018 and 2019, DOC was inversely correlated with salinity (r2 = 0.97) and positively correlated with dissolved organic matter fluorescence (fDOM; r2 = 0.67). DOC showed strong correlation with the nonparticulate absorption coefficient at 440 nm (ag(440)) only in 2018 (r2 = 0.95). The vertical structure of fDOM in Stefansson Sound aligned with density profiles more strongly in 2018 than in 2019, and higher levels of fDOM, ag(440), and backscatter seen near the bottom in 2019 suggest wind‐driven mixing and/or bottom resuspension events. In both years, DOC correlated strongly with the spectral slope of the absorption coefficient between 412 and 550 nm (r2 = 0.70), and POC was well correlated with spectral backscattering at 470, 532, and 660 nm (r2 = 0.90, 0.71, and 0.59). These interannual differences in the spatial and vertical distributions of DOC and POC, and their respective correlations with optical proxies, likely reflect regional climatological factors such as precipitation over the adjacent watersheds, wind patterns, and residual sea ice in late summer.