Elson Lagoon Research Articles

Modes of Weather System-Induced Flows through an Arctic Lagoon

With the increasing warming of the Arctic, the summertime ice-free period in the coastal Arctic becomes longer and the water exchange between arctic lagoons and coastal Beaufort Sea becomes more important for land–ocean interaction. This study examined the dynamics of water exchange between the arctic lagoons and the Arctic Ocean under the influence of weather systems (the transient arctic cyclones and hovering Beaufort High pressure system). We implemented rare observations, numerical modeling with the Finite Volume Community Ocean Model (FVCOM), and a forcing-response Empirical Orthogonal Function (fr-EOF) analysis to determine the weather-driven flow patterns and characteristics in the micro-tidal arctic lagoon (Elson Lagoon) with little freshwater discharge. The results were validated for both tidal and subtidal currents with in situ data. The inlets of the lagoon were significantly impacted by wind associated with the weather systems and the flows through the inlets were highly correlated with each other. The fr-EOF analysis for the 1.5-month FVCOM output indicated three significant modes of wind-driven flow. In the deepest (~16 m) northwestern-most inlet, a counter-wind flow occurred more than 96% of the time due to setup and set down of water level inside the lagoon and the vorticity balance related to the wind stress and water depth. For about 60–80% of the time, the exchange flow was out of the lagoon through the northwestern-most and deepest inlet due to the strong easterly winds dictated by the Beaufort High; this dominant flow is mainly caused by the persistent easterly wind as a limb of the Beaufort High pressure system, modified by the transient arctic cyclones with a westerly wind and inward flows at the westernmost inlet of Elson Lagoon. This study shows that the alternating influence from the cyclone-anticyclone weather systems produces a meteorological tide in the subtidal spectrum which dominates the water exchange in the region through the multiple inlets. With the observed increase in cyclone strength and frequency under the warming trend, this may imply a greater contribution from the westerly wind because of the increased cyclonic activities. If this is the case, the inward flow might increase and have an effect on sediment, larval, and nutrient transports through this system.

Remotely Monitored Buoys for Observing the Growth and Development of Sea Ice In Situ

Abstract This paper describes a remotely monitored buoy that, when deployed in open water prior to freeze up, permits scientists to monitor not only temperature with depth, and hence freeze up and sea ice thickness, but also the progression of sea ice development—e.g., the extent of cover at a given depth as it grows (solid fraction), the brine volume of the ice, and the salinity of the water just below, which is driven by brine expulsion. Microstructure and In situ Salinity and Temperature (MIST) buoys use sensor “ladders” that, in our prototypes, extend to 88 cm below the surface. We collected hourly measurements of surface air temperature and water temperature and electrical impedance every 3 cm to track the seasonal progression of sea ice growth in Elson Lagoon (Utqiaġvik, Alaska) over the 2017/18 ice growth season. The MIST buoy has the potential to collect detailed sea ice microstructural information over time and help scientists monitor all parts of the growth/melt cycle, including not only the freezing process but the effects of meteorological changes, changing snow cover, the interaction of meltwater, and drainage. Significance Statement There is a need to better understand how an increasing influx of freshwater, one part of a changing Arctic climate, will affect the development of sea ice. Current instruments can provide information on the growth rate, extent, and thickness of sea ice, but not direct observations of the structure of the ice during freeze up, something that is tied to salinity and local air and water temperature. A first deployment in Elson Lagoon in Utqiaġvik, Alaska, showed promising results; we observed fluctuations in ice temperatures in response to brief warmings in air temperature that resulted in changes in the conductivity, liquid fraction, and brine volume fraction within the ice.

Nearshore bathymetric changes along the Alaska Beaufort Sea coast and possible physical drivers

Erosion rates along Alaska's Beaufort Sea coast, among the highest in the world, are negatively impacting communities, industrial and military infrastructure, and wildlife habitat. Decreasing maximal winter ice extent and increasing summer open water duration and extent in the Beaufort Sea may be making the coast more vulnerable to destructive storm waves than during recent, colder, icier decades. Previous studies of Beaufort Sea coastal change have been limited to subaerial analyses of the shoreline. Here we describe nearshore seafloor change by comparing post-World War II (WWII) (1945-53) bathymetry data to recently acquired (1985–2018) bathymetry data and relate the observed seafloor change to adjacent shoreline change near Utqiagvik, within Stefansson Sound, and immediately west of Barter Island and Kaktovik. Within the Utqiagvik region, seabed erosion was generally highest (>1.0 m of loss) offshore of Point Barrow and along the eastern end of the Tapkaluk Islands, while there were lesser amounts of deposition (<0.5 m of gain) within the protected waters of Elson Lagoon. Sedimentation was generally highest offshore of Point Barrow, in a region of converging currents, and on the landward side of the barrier islands and spits fronting Elson Lagoon, which is likely related to a regional trend of westerly sediment transport and landward migration of the barrier islands. Within Stefansson Sound, perhaps the most notable changes from post-WWII bathymetry data compared to recent data are a switch from mixed, low erosion and deposition in 1997 to low deposition (<0.5 m) in 2018 east of the Boulder Patch, a switch from low erosion in 1997 to neutral depth change in 2018 in the channel between the north and south Boulder Patch areas, and higher deposition from 1997 to 2018 landward of the rapidly retreating barrier islands along the Sound's northern border. At Barter Island, high erosion near north-facing shorelines and high deposition near west-facing shorelines generally matched shoreline changes. One of our goals is to identify possible processes responsible for the depth changes we quantified. Using simple metrics that relate sediment characteristics with modeled waves and non-wave induced currents, we show that sediment resuspension and transport by both wave and non-wave driven currents likely contribute to the overall patterns of change within the ∼13 m isobath along the open coast, and that the influence of wave action affecting sediment transport is expanding seaward.

Increasing freshwater and dissolved organic carbon flows to Northwest Alaska’s Elson lagoon

Manifestations of climate change in the Arctic are numerous and include hydrological cycle intensification and permafrost thaw, both expected as a result of atmospheric and surface warming. Across the terrestrial Arctic dissolved organic carbon (DOC) entrained in arctic rivers may be providing a carbon subsidy to coastal food webs. Yet, data from field sampling is too often of limited duration to confidently ascertain impacts of climate change on freshwater and DOC flows to coastal waters. This study applies numerical modeling to investigate trends in freshwater and DOC exports from land to Elson Lagoon in Northwest Alaska over the period 1981–2020. While the modeling approach has limitations, the results point to significant increases in freshwater and DOC exports to the lagoon over the past four decades. The model simulation reveals significant increases in surface, subsurface (suprapermafrost), and total freshwater exports. Significant increases are also noted in surface and subsurface DOC production and export, influenced by warming soils and associated active-layer thickening. The largest changes in subsurface components are noted in September, which has experienced a ∼50% increase in DOC export emanating from suprapermafrost flow. Direct coastal suprapermafrost freshwater and DOC exports in late summer more than doubled between the first and last five years of the simulation period, with a large anomaly in September 2019 representing a more than fourfold increase over September direct coastal export during the early 1980s. These trends highlight the need for dedicated measurement programs that will enable improved understanding of climate change impacts on coastal zone processes in this data sparse region of Northwest Alaska.

Spatiotemporal variation of environmental conditions and prey availability that drive Arctic nearshore fish community structure in the Point Barrow, Alaska, region

The Arctic nearshore surrounding Point Barrow, Alaska, is a dynamic system with complex oceanographic and meteorological processes that drive community composition to change rapidly in space and time. Nearshore fish and zooplankton communities were sampled in the summers of 2013–2015. Spatial, temporal, environmental, and biological drivers of fish community structure in the Arctic nearshore surrounding Point Barrow were investigated using multivariate canonical correspondence analysis (CCA). A CCA model using the 13 most explanatory variables (three environmental, one spatial, four temporal, and five zooplankton abundances) explained 73% of the variance in community structure in this region. Distinct fish communities were identified within the three waterbodies that were studied (Chukchi Sea, Beaufort Sea, and Elson Lagoon), and these distinctions were largely driven by salinity. Species move into the nearshore at various times after landfast ice breaks up, creating an annual succession of species that can be found in these nearshore habitats. Low-latitude species tend to become abundant later in the summer season, whereas true Arctic species are present under the ice or move in shortly after breakup. Arctic species are also more abundant in colder years, whereas low-latitude species dominate during warmer years. The increasing abundance of low-latitude species in the Arctic nearshore may have serious implications for the food webs in these ecosystems as climate change continues.

Brief communication: An alternative method for estimating the scavenging efficiency of black carbon by meltwater over sea ice

Abstract. The meltwater scavenging coefficient (MSC) of black carbon (BC) is a crucial parameter in snow and sea ice models, as it determines the BC enrichment in the surface layer of melting snow over sea ice and therefore modulates the BC–snow–albedo feedbacks. We present a new method for MSC estimation by sampling the melt–refreeze ice layer that is produced from refreezing of the meltwater within snowpack and its overlying snow and measuring their physical characteristics in Elson Lagoon northeast of Utqiaġvik (formerly Barrow), Alaska, during the melting season. The bias of estimated MSC ranges from −5.4 % to 7.3 %, which is not exactly dependent on the degree of ablation. The average MSC value calculated with this proposed method is slightly lower than that derived from the repeating sampling (RS) method in Elson Lagoon while still being within its best estimate range. Further estimation demonstrates that the MSC in the Canada Basin (23.6 %±2.1 %) is close to that in Greenland (23.0 %±12.5 %) and larger than that in the Chukchi Sea (17.9 %±5.0 %) in the northwest of Utqiaġvik. Elson Lagoon has the lowest MSC (14.5 %±2.6 %) in the study areas. The method suggested in this study provides a possible approach for large-scale measurements of MSC over the sea ice area in the Arctic. Of course, this method depends on the presence of a melt–refreeze ice layer in the observation area.

Physical length scales of wind-blown snow redistribution and accumulation on relatively smooth Arctic first-year sea ice

Snow thickness measurements over relatively smooth Arctic first-year sea ice, obtained near Cambridge Bay in the Canadian Arctic (2014, 2016 and 2017) and near Elson Lagoon in the Alaskan Arctic (2003 and 2006), are analyzed to quantify physical length-scales and their relevant scaling behaviors. We use the multi-fractal temporally weighted detrended fluctuation analysis method to detect two major physical length-scales from the two independent study locations. Our results suggest that physical processes underlying the formation of snow dunes are consistent and that the wind is the main process shaping the snow thickness variability and redistribution. One scale, around 10 m, appears to be related to the formation of the snow ‘dunes’, while the other scale, between 30 and 100 m, is likely associated with the various interactions of the snow dunes such as merging, calving and lateral linking. Results imply that snow on level sea ice shows self-organized characteristics.

Weather induced subtidal flows through multiple inlets of an arctic microtidal lagoon

Estuarine processes in the arctic lagoons are among the least studied but important subjects, especially considering the rapid warming of arctic water which may change the length of ice-free period in the summer. In this paper, wind-driven exchange flows in the micro-tidal Elson Lagoon of northern Alaska with multiple inlets of contrasting widths and depths are studied with in situ observations, statistical analysis, numerical experiments, a regression model on the basis of dynamics, and remote sensing data. Water velocity profiles were obtained from a bottom deployed acoustic Doppler current profiler (ADCP) in the northwestern Eluitkak Pass connecting the Beaufort Sea to the Elson Lagoon during a 4.9 day ice-free period in the summer of 2013. The subtidal flow is found correlated with wind (R2 value ~96%). Frequently occurring east, northeast and north winds from the arctic atmospheric high- and low-pressure systems push water from the Beaufort Sea into the lagoon through the wide inlets on the eastern side of the lagoon, resulting in an outward flow against the wind at the narrow northwestern inlet. The counter-wind flow is a result of an uneven wind forcing acting through the asymmetric inlets and depth, an effect of “torque” or vorticity. Under northwest wind, the exchange flow at the northwestern inlet reverses its direction, with inward flows through the upwind northwestern inlet and outward flows through the downwind eastern inlets. A regression model is established based on the momentum equations and Taylor series expansions. The model is used to predict flows in July and August of 2015 and July of 2017, supported by available Landsat satellite images. About 73%–80% of the time the flows at Eluitkak Pass are out of Elson Lagoon for the summer of 2015 and 2017. Numerical experiments are conducted to corroborate the findings and illustrate the effects under various wind conditions. A quasi-steady state balance between wind force and surface pressure gradient is confirmed.

Mapping Arctic Bottomfast Sea Ice Using SAR Interferometry

Bottomfast sea ice is an integral part of many near-coastal Arctic ecosystems with implications for subsea permafrost, coastal stability and morphology. Bottomfast sea ice is also of great relevance to over-ice travel by coastal communities, industrial ice roads, and marine habitats. There are currently large uncertainties around where and how much bottomfast ice is present in the Arctic due to the lack of effective approaches for detecting bottomfast sea ice on large spatial scales. Here, we suggest a robust method capable of detecting bottomfast sea ice using spaceborne synthetic aperture radar interferometry. This approach is used to discriminate between slowly deforming floating ice and completely stationary bottomfast ice based on the interferometric phase. We validate the approach over freshwater ice in the Mackenzie Delta, Canada, and over sea ice in the Colville Delta and Elson Lagoon, Alaska. For these areas, bottomfast ice, as interpreted from the interferometric phase, shows high correlation with local bathymetry and in-situ ice auger and ground penetrating radar measurements. The technique is further used to track the seasonal evolution of bottomfast ice in the Kasegaluk Lagoon, Alaska, by identifying freeze-up progression and areas of liquid water throughout winter.

Evaluating landfast sea ice stress and fracture in support of operations on sea ice using SAR interferometry

Recent Arctic warming has led to reduced sea-ice thickness and a more dynamic landfast ice cover with potential widespread consequences for ice users. Here, we develop an approach to assess the small-scale deformation of landfast ice critical to on-ice operations using synthetic aperture radar interferometry (InSAR). InSAR has previously proven successful in determining long-term qualitative climatology of ice deformation around on-ice operations, but is now used to explore its potential for providing quantitative guidance for ice road planning, construction, and maintenance. A validation effort using X-band SAR and high-precision GPS data over Elson Lagoon, Alaska, confirms the ability of InSAR to accurately estimate 3-dimensional sea ice strain values accumulated between SAR image acquisitions, using an inverse model. The inverse model was further applied to L-band InSAR data over the Northstar Island ice road near Prudhoe Bay, Alaska. Assuming an elasto-brittle rheology, the derived strain values yielded a spatial distribution of internal stress consistent with preexisting ice defects and morphology. In several localized regions of the study area, stress values exceeded expected yield stress. Resulting relative fracture intensity potential was shown to conform with local knowledge based on road inspections by engineers, and may be used to guide ice road planning, construction and maintenance efforts. The results presented here demonstrate that InSAR is an accurate tool for estimating landfast ice deformation and stability in support of ice use. The findings may also provide substantial new insights into the mechanics of landfast ice.

Geostatistical and Statistical Classification of Sea-Ice Properties and Provinces from SAR Data

Recent drastic reductions in the Arctic sea-ice cover have raised an interest in understanding the role of sea ice in the global system as well as pointed out a need to understand the physical processes that lead to such changes. Satellite remote-sensing data provide important information about remote ice areas, and Synthetic Aperture Radar (SAR) data have the advantages of penetration of the omnipresent cloud cover and of high spatial resolution. A challenge addressed in this paper is how to extract information on sea-ice types and sea-ice processes from SAR data. We introduce, validate and apply geostatistical and statistical approaches to automated classification of sea ice from SAR data, to be used as individual tools for mapping sea-ice properties and provinces or in combination. A key concept of the geostatistical classification method is the analysis of spatial surface structures and their anisotropies, more generally, of spatial surface roughness, at variable, intermediate-sized scales. The geostatistical approach utilizes vario parameters extracted from directional vario functions, the parameters can be mapped or combined into feature vectors for classification. The method is flexible with respect to window sizes and parameter types and detects anisotropies. In two applications to RADARSAT and ERS-2 SAR data from the area near Point Barrow, Alaska, it is demonstrated that vario-parameter maps may be utilized to distinguish regions of different sea-ice characteristics in the Beaufort Sea, the Chukchi Sea and in Elson Lagoon. In a third and a fourth case study the analysis is taken further by utilizing multi-parameter feature vectors as inputs for unsupervised and supervised statistical classification. Field measurements and high-resolution aerial observations serve as basis for validation of the geostatistical-statistical classification methods. A combination of supervised classification and vario-parameter mapping yields best results, correctly identifying several sea-ice provinces in the shore-fast ice and the pack ice. Notably, sea ice does not have to be static to be classifiable with respect to spatial structures. In consequence, the geostatistical-statistical classification may be applied to detect changes in ice dynamics, kinematics or environmental changes, such as increased melt ponding, increased snowfall or changes in the equilibrium line.

Spatial and temporal variability of air-sea CO2 exchange of alongshore waters in summer near Barrow, Alaska

Alongshore water off Barrow, Alaska is a useful area for studying the carbon cycle of the Arctic coastal sea, because the different coastal characteristics extant in the area likely represent much larger regions of the coastal water of the western Arctic Ocean. Especially noteworthy is the inflow shelf water transferred northward by the Arctic Coastal Current into the Chukchi Sea from the North Pacific and turbid water in the Elson Lagoon where a significant amount of coastal erosion has been reported along the extensive coastal line and where a part of the water from the lagoon drains into the Beaufort Sea adjacent to the Chukchi Sea. To investigate spatial and temporal variations of air-sea CO2 flux (CO2 flux) of the alongshore water, partial pressure of CO2 of surface seawater (pCO2sw) was measured in summer, 2007 and 2008, and CO2 flux was directly measured by eddy covariance at a fixed point for the Beaufort Sea in summer 2008. Measured pCO2sw in the Chukchi Sea side was the lowest in the beginning of the measurement season and increased later in the season both in 2007 and 2008. The average CO2 flux estimated based on pCO2sw in the Chukchi Sea side was −0.10 μmol m−2 s−1 (±0.1 s.d.) using the sign convention of positive fluxes into the atmosphere from the ocean. pCO2sw in the Beaufort Sea and the Elson Lagoon was relatively higher in early summer and decreased in the middle of the summer. The overall average CO2 flux was −0.07 μmol m−2 s−1 (±0.1 s.d.) for the Beaufort Sea side and −0.03 μmol m−2 s−1 (±0.07 s.d.) for the Elson Lagoon respectively, indicating a sink of CO2 despite high carbon inflows from the terrestrial margin into the Elson Lagoon. A strong sink of CO2 was often observed from the Beaufort Sea by eddy covariance in the middle of the summer. This sink activity in the middle summer in the Beaufort Sea and Elson Lagoon was likely due to biological carbon uptake as inferred by low apparent oxygen utilization and high chlorophyll concentration that offset a potential source of CO2 due to terrestrial carbon inputs.

Historical changes in trace metals and hydrocarbons in nearshore sediments, Alaskan Beaufort Sea, prior and subsequent to petroleum-related industrial development: Part II. Hydrocarbons

Composition and concentration of hydrocarbons (normal and isoprenoid alkanes, triterpenoids, steranes, and PAHs) in nearshore surface sediments from Elson Lagoon (EL), Colville Delta–Prudhoe Bay (CDPB) and Beaufort Lagoon (BL), Alaskan Beaufort Sea, were assessed for spatio-temporal variability. Principal component analysis of the molecules/biomarkers concentrations delineated CDPB and BL samples into two groups, and cluster analysis identified three station groups in CDPB. Overall there was no geographic distribution pattern in the groups. The diversities between groups and individual samples are attributed to differences in n-alkanes and PAHs contents, which are influenced predominantly by sediment granulometry and sitespecific fluvial input. The predominant hydrocarbon source is biogenic, mainly terrigenous, with hardly any contribution from natural oil seeps, oil drill effluents and/or refined crude. The terrigenous source is corroborated by δ13C, δ15N, and OC/N of sediment organic matter. Time interval (1976–1977, 1984 and 1997) changes in hydrocarbon compositions and concentrations in CDPB are not significant.

Historical changes in trace metals and hydrocarbons in nearshore sediments, Alaskan Beaufort Sea, prior and subsequent to petroleum-related industrial development: Part I. Trace metals

Concentrations of Fe, As, Ba, Cd, Cu, Cr, Pb, Mn, Ni, Sn, V and Zn in mud (<63μm size), and total and methyl Hg in gross sediment are reported for Arctic Alaska nearshore. Multivariate-PCA analysis discriminated seven station clusters defined by differences in metal concentrations, attributed to regional variations in granulometry and, as in Elson Lagoon, to focused atmospheric fluxes of contaminants from Eurasia. In Colville Delta-Prudhoe Bay, V increase was noted in 1985 and 1997 compared to 1977, and Ba increase from 1985 to 1997. Presumably the source of increased V is the local gas flaring plant, and the elevated Ba is due to barite accumulation from oil drilling effluents. In Prudhoe Bay, concentration spikes of metals in ∼1988 presumably reflect enhanced metals deposition following maximum oil drilling in 1980s. In summary, the Alaskan Arctic nearshore has remained generally free of metal contamination despite petroleum-related activities in past 40years.

A Comparison of Snow Depth on Sea Ice Retrievals Using Airborne Altimeters and an AMSR-E Simulator

A comparison of snow depths on sea ice was made using airborne altimeters and an Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSR-E) simulator. The data were collected during the March 2006 National Aeronautics and Space Administration (NASA) Arctic field campaign utilizing the NASA P-3B aircraft. The campaign consisted of an initial series of coordinated surface and aircraft measurements over Elson Lagoon, Alaska and adjacent seas followed by a series of large-scale (100 km × 50 km) coordinated aircraft and AMSR-E snow depth measurements over portions of the Chukchi and Beaufort seas. This paper focuses on the latter part of the campaign. The P-3B aircraft carried the University of Colorado Polarimetric Scanning Radiometer (PSR-A), the NASA Wallops Airborne Topographic Mapper (ATM) lidar altimeter, and the University of Kansas Delay-Doppler (D2P) radar altimeter. The PSR-A was used as an AMSR-E simulator, whereas the ATM and D2P altimeters were used in combination to provide an independent estimate of snow depth. Results of a comparison between the altimeter-derived snow depths and the equivalent AMSR-E snow depths using PSR-A brightness temperatures calibrated relative to AMSR-E are presented. Data collected over a frozen coastal polynya were used to intercalibrate the ATM and D2P altimeters before estimating an altimeter snow depth. Results show that the mean difference between the PSR and altimeter snow depths is -2.4 cm (PSR minus altimeter) with a standard deviation of 7.7 cm. The RMS difference is 8.0 cm. The overall correlation between the two snow depth data sets is 0.59.

Geoelectric observations of the degradation of nearshore submarine permafrost at Barrow (Alaskan Beaufort Sea)

Submarine permafrost degradation rates may be determined by a number of interacting processes, including rates of sea level rise and coastal erosion, sea bottom temperature and salinity regimes, geothermal heat flux and heat and mass diffusion within the sediment column. Observations of ice‐bearing permafrost in shelf sediments are necessary in order to determine its spatial distribution and to quantify its degradation rate. We tested the use of direct current electrical resistivity to ice‐bearing permafrost in Elson Lagoon northeast of Barrow, Alaska (Beaufort Sea). A sharp increase in electrical resistivity was observed in profiles collected perpendicular to and along the coastline and is interpreted to be the boundary between ice‐free sediment and underlying ice‐bearing submarine permafrost. The depth to the interpreted ice‐bearing permafrost increases from &lt;2 m below sea level to over 12 m below sea level with increasing distance from the coastline. The dependence of the saline sediment electrical resistivity on temperature and freezing was measured in the laboratory to provide validation for the field measurements. Electrical resistivity was shown to be effective for detection of shallow ice‐bearing permafrost in the coastal zone. Historical coastal retreat rates were combined with the inclination of the top of the ice‐bearing permafrost to calculate mean vertical permafrost degradation rates of 1 to 4 cm yr−1.

A low power automated MAX-DOAS instrument for the Arctic and other remote unmanned locations

Abstract. Multiple Axis Differential Optical Absorption Spectrometer (MAX-DOAS) systems are inherently very simple instruments, which have been shown to provide extremely useful information about a wide variety of environmental parameters. In order to exploit the potential of the technique we have developed a new field-deployable, passive MAX-DOAS system that is automated and uses little power (&lt;3 W). This new instrument utilizes a fully enclosed scan head that protects all moving parts and optics from harsh environments. Instrument diagnostics, such as tilt monitoring and frost accumulation detection and removal, are integrated into the main data acquisition program, which then acts to remedy problems that were discovered. This full automation and data quality checking make this instrument ideal for long-term deployment at remote, unmanned locations around the world, such as in polar regions or in the monitoring of trace gas emissions from volcanoes. This instrument was recently integrated into an ice-tethered autonomous buoy and tested in Elson Lagoon, near Barrow, Alaska to monitor halogen chemistry in the Arctic. During this investigation, differential slant column densities (dSCDs) of BrO up to 6×1014 molecules/cm2 were observed. Typical spectral fit residual RMS optical densities were less than 6×10−4 for solar zenith angles (SZA) &lt;80° and a 6-min integration time. Here we describe the design concepts and performance of this new MAX-DOAS instrument through detailed analyses of spectral quality, power usage, possible instrument response biases, and typical instrument operations.

Simultaneous retrieval of aerosol and surface optical properties from combined airborne- and ground-based direct and diffuse radiometric measurements

Abstract. This paper presents a new method for simultaneously retrieving aerosol and surface reflectance properties from combined airborne and ground-based direct and diffuse radiometric measurements. The method is based on the standard Aerosol Robotic Network (AERONET) method for retrieving aerosol size distribution, complex index of refraction, and single scattering albedo, but modified to retrieve aerosol properties in two layers, below and above the aircraft, and parameters on surface optical properties from combined datasets (Cloud Absorption Radiometer (CAR) and AERONET data). A key advantage of this method is the inversion of all available spectral and angular data at the same time, while accounting for the influence of noise in the inversion procedure using statistical optimization. The wide spectral (0.34–2.30 μm) and angular range (180°) of the CAR instrument, combined with observations from an AERONET sunphotometer, provide sufficient measurement constraints for characterizing aerosol and surface properties with minimal assumptions. The robustness of the method was tested on observations made during four different field campaigns: (a) the Southern African Regional Science Initiative 2000 over Mongu, Zambia, (b) the Intercontinental Transport Experiment-Phase B over Mexico City, Mexico (c) Cloud and Land Surface Interaction Campaign over the Atmospheric Radiation Measurement (ARM) Central Facility, Oklahoma, USA, and (d) the Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) over Elson Lagoon in Barrow, Alaska, USA. The four areas are dominated by different surface characteristics and aerosol types, and therefore provide good test cases for the new inversion method.

Development of an autonomous sea ice tethered buoy for the study of ocean-atmosphere-sea ice-snow pack interactions: the O-buoy

Abstract. A buoy based instrument platform (the "O-buoy") was designed, constructed, and field tested for year-round measurement of ozone, bromine monoxide, carbon dioxide, and meteorological variables over Arctic sea ice. The O-buoy operated in an autonomous manner with daily, bi-directional data transmissions using Iridium satellite communication. The O-buoy was equipped with three power sources: primary lithium-ion battery packs, rechargeable lead acid packs, and solar panels that recharge the lead acid packs, and can fully power the O-buoy during summer operation. This system was designed to operate under the harsh conditions present in the Arctic, with minimal direct human interaction, to aid in our understanding of the atmospheric chemistry that occurs in this remote region of the world. The current design requires approximately yearly maintenance limited by the lifetime of the primary power supply. The O-buoy system was field tested in Elson Lagoon, Barrow, Alaska from February to May 2009, and deployed in the Beaufort Sea in October 2009. Here, we describe the design and present preliminary data.

Summer landfast sea ice desalination at Point Barrow, Alaska: Modeling and observations

Landfast sea ice cores from two sites in Point Barrow, Alaska, extracted between 1999 and 2001, show a progressive desalination and a corresponding shape transition in the salinity profile starting at snowmelt onset, around 1 June. The vertical percolation of fresh surface meltwater through the permeable ice matrix (flushing) has long been supposed to control this transition. A parameterization of flushing in bare ice is formulated. It is incorporated into the semiempirical winter sea ice desalination model of Cox and Weeks (1988), coupled to the one‐dimensional thermodynamic sea ice model of Bitz and Lipscomb (1999) and forced under Point Barrow conditions. Adjustment to the original Cox and Weeks parameterization of gravity drainage was necessary to give reasonable agreement with observations in winter. With this change the model has the potential to simulate the full seasonal cycle of the Arctic salinity and mass balance of typical Arctic ice. In summer, the model salinity profile closely follows the observations. The model upper ice temperatures are slightly too cold. At the thin snow (Chukchi Sea) site, the model simulates the observed snow depth and ice thickness well. At the thick snow (Elson Lagoon) site, the snow disappears 7 days earlier than observed, which results in underestimating ice thickness. Sensitivity experiments suggest that a more realistic representation of snow and meltwater physics would significantly improve the simulation. Because of the effects of brine drainage on the sea ice mass balance and oceanic circulation, including the time dependence of the ice salinity profile would significantly improve the next generation of sea ice models.