Arctic Observations Research Articles

Improving coordination and integration of observations of Arctic change

U.S. Arctic Observing Coordination Workshop;Anchorage, Alaska, 20–22 March 2012 The Arctic is undergoing tremendous changes. Permafrost is thawing, ice sheets are melting, and sea ice is thinning and retreating. These changes are impacting ecosystems and human activities. Observing, understanding, and responding to these changes are the central themes of the U.S. Interagency Study of Environmental Arctic Change (SEARCH, http://www.arcus.org/search/index.php). SEARCH brings together academic and government agency scientists and stakeholders to prioritize, plan, conduct, and synthesize research focused on Arctic environmental change. The U.S. Arctic Observing Coordination Workshop (http://www.arcus.org/search/meetings/2012/coordination‐workshop/) focused on two key themes for cross‐disciplinary and cross‐agency collaboration: (1) understanding and predicting sea ice changes and their consequences for ecosystems, human activities, and climate and (2) determining consequences of loss and warming of shallow permafrost on Arctic and global systems.

On the Relationship between Thermodynamic Structure and Cloud Top, and Its Climate Significance in the Arctic

Abstract Cloud and thermodynamic characteristics from three Arctic observation sites are investigated to understand the collocation between low-level clouds and temperature inversions. A regime where cloud top was 100–200 m above the inversion base [cloud inside inversion (CII)] was frequently observed at central Arctic Ocean sites, while observations from Barrow, Alaska, indicate that cloud tops were more frequently constrained to inversion base height [cloud capped by inversion (CCI)]. Cloud base and top heights were lower, and temperature inversions were also stronger and deeper, during CII cases. Both cloud regimes were often decoupled from the surface except for CCI over Barrow. In-cloud lapse rates differ and suggest increased cloud-mixing potential for CII cases. Specific humidity inversions were collocated with temperature inversions for more than 60% of the CCI and more than 85% of the CII regimes. Horizontal advection of heat and moisture is hypothesized as an important process controlling thermodynamic structure and efficiency of cloud-generated motions. The portion of CII clouds above the inversion contains cloud radar signatures consistent with cloud droplets. The authors test the longwave radiative impact of cloud liquid above the inversion through hypothetical liquid water distributions. Optically thin CII clouds alter the effective cloud emission temperature and can lead to an increase in surface flux on the order of 1.5 W m−2 relative to the same cloud but whose top does not extend above the inversion base. The top of atmosphere impact is even larger, increasing outgoing longwave radiation up to 10 W m−2. These results suggest a potentially significant longwave radiative forcing via simple liquid redistributions for a distinctly dominant cloud regime over sea ice.

Correlation between present‐day model simulation of Arctic cloud radiative forcing and sea ice consistent with positive winter convective cloud feedback

A positive feedback on winter sea‐ice loss, based on warming due to radiative forcing caused by the onset of convective clouds in response to sea‐ice loss, has recently been proposed. This feedback has thus far been investigated using a hierarchy of climate models in high CO2 scenarios. This paper examines the possibility that such feedback may be active within present‐day like Arctic variability, using model output from two reanalysis models. It is emphasized that Arctic surface fluxes, radiative fluxes and clouds are effectively unconstrained by observations in reanalysis products. Consequently, the results here should be viewed only as a model study of the feedback in present‐day model climate variability. Model winter sea ice and cloud radiative forcing are found to co‐vary strongly and locally, consistent with a strong convective cloud feedback, which may contribute to sea ice variability. Furthermore, the anti‐correlation between the two variables is found to be as strong in the model output analyzed here as in the IPCC global climate models that simulate the convective cloud feedback most strongly at high CO2. In those IPCC models the convective cloud feedback contributes to a total loss of winter sea ice in a CO2 quadrupling scenario. These results do not necessarily prove that this feedback exists in the present‐day Arctic and demonstrating this will require further study using actual Arctic observations.

Evaluation of Polar WRF forecasts on the Arctic System Reanalysis Domain: 2. Atmospheric hydrologic cycle

The forecast atmospheric hydrologic cycle of the Polar version 3.1.1 of the Weather Research and Forecasting model (WRF) is examined for December 2006 – November 2007. The domain is similar to the Arctic System Reanalysis (ASR), an assimilation of model fields and Arctic observations being conducted partly by the Byrd Polar Research Center. Simulations are performed in 48 h increments initialized daily at 0000 UTC, with the first 24 h discarded for model spin‐up of the hydrologic cycle and boundary layer processes. Precipitation analysis reveals a negative annual mean bias (−9.4%) in the polar region, with particularly dry station biases reflected in the Canadian Archipelago. Annual mean bias for the midlatitudes is small and positive (4.6%), attributed to excessive precipitation during spring and summer when convective precipitation is dominant. An examination of precipitation within four major Arctic river basins shows large positive biases due to excessive convective precipitation in summer as well, but highlights the Arctic climate's strong dependence on midlatitude precipitation. Nudging the model's boundary layer moisture toward drier conditions decreases convective precipitation improving the prediction. Cloud fraction analysis shows too little cloud cover, supported by an excess in incident shortwave radiation and a deficit in downwelling longwave radiation throughout the domain. The longwave bias is present regardless of the amount of cloud water or cloud ice, demonstrating a need to improve cloud effects on radiation in Polar WRF. This examination provides a benchmark of the forecast atmospheric hydrological cycle of Polar WRF and its use as ASR's primary model.

Trends of solar ultraviolet irradiance at Barrow, Alaska, and the effect of measurement uncertainties on trend detection

Abstract. Spectral ultraviolet (UV) irradiance has been observed near Barrow, Alaska (71° N, 157° W) between 1991 and 2011 with an SUV-100 spectroradiometer. The instrument was historically part of the US National Science Foundation's UV Monitoring Network and is now a component of NSF's Arctic Observing Network. From these measurements, trends in monthly average irradiance and their uncertainties were calculated. The analysis focuses on two quantities, the UV Index (which is affected by atmospheric ozone concentrations) and irradiance at 345 nm (which is virtually insensitive to ozone). Uncertainties of trend estimates depend on variations in the data due to (1) natural variability, (2) systematic and random errors of the measurements, and (3) uncertainties caused by gaps in the time series. Using radiative transfer model calculations, systematic errors of the measurements were detected and corrected. Different correction schemes were tested to quantify the sensitivity of the trend estimates on the treatment of systematic errors. Depending on the correction method, estimates of decadal trends changed between 1.5% and 2.9%. Uncertainties in the trend estimates caused by error sources (2) and (3) were set into relation with the overall uncertainty of the trend determinations. Results show that these error sources are only relevant for February, March, and April when natural variability is low due to high surface albedo. This method of addressing measurement uncertainties in time series analysis is also applicable to other geophysical parameters. Trend estimates varied between −14% and +5% per decade and were significant (95.45% confidence level) only for the month of October. Depending on the correction method, October trends varied between −11.4% and −13.7% for irradiance at 345 nm and between −11.7% and −14.1% for the UV Index. These large trends are consistent with trends in short-wave (0.3–3.0 μm) solar irradiance measured with pyranometers at NOAA's Barrow Observatory and can be explained by a change in snow cover over the observation period: analysis of pyranometer data indicates that the first day of fall when albedo becomes larger than 0.6 after snow fall, and remains above 0.6 for the rest of the winter, has advanced with a statistically significant trend of 13.6 ± 9.7 days per decade.

Evaluation of Polar WRF forecasts on the Arctic System Reanalysis domain: Surface and upper air analysis

[1] The Polar version 3.1.1 of the Weather Research and Forecasting model (WRF), a high-resolution regional scale model, is used to simulate conditions for the year December 2006 to November 2007. The goal is to compare model output of near-surface and tropospheric variables to observational data sets. The domain mirrors that of the Arctic System Reanalysis (ASR), an assimilation of model fields with Arctic observations being conducted partly by the Polar Meteorology Group of the Byrd Polar Research Center at Ohio State University. A key development in this Polar WRF study is the extension of the seasonal progression of sea ice albedo to the entire Arctic Ocean. The boundary conditions are specified by the NCEP Final global gridded analysis archive (FNL), a 1° × 1° global grid updated every 6 h. The simulations are performed in 48 h increments initialized daily at 0000 UTC, with the first 24 h discarded for model spin-up of the hydrologic cycle and boundary layer processes. Model large-scale variables of atmospheric pressure and geopotential height show good agreement with observations. Spatial distribution of near-surface air temperatures compares well with ERA-Interim despite a small negative bias in the station analysis. Surface dewpoint temperatures and wind speeds show small biases, but model skill is modest for near-surface winds. Tropospheric temperatures and wind speeds, however, agree well with radiosonde observations. This examination provides a benchmark from which to improve the model and guidance for further development of Polar WRF as ASR's primary model.

Synoptically Driven Arctic Winter States

Abstract The dense network of the Surface Heat Budget of the Arctic (SHEBA) observations is used to assess relationships between winter surface and atmospheric variables as the SHEBA site came under the influence of cyclonic and anticyclonic atmospheric circulation systems. Two distinct and preferred states of subsurface, surface, atmosphere, and clouds occur during the SHEBA winter, extending from the oceanic mixed layer through the troposphere and preceded by same-sign variations in the stratosphere. These states are apparent in distributions of surface temperature, sensible heat and longwave radiation fluxes, ocean heat conduction, cloud-base height and temperature, and in the atmospheric humidity and temperature structure. Surface and atmosphere are in radiative–turbulent–conductive near-equilibrium during a warm opaquely cloudy-sky state, which persists up to 10 days and usually occurs during the low surface pressure phase of a baroclinic wave, although occasionally occurs during the high surface pressure phase because of low, scattered clouds. Clouds occurring in this state have near-unity emissivity and the lowest bases in the vicinity of, or below, the temperature inversion peak. A cold radiatively clear-sky state persists up to two weeks, and occurs only in the high surface pressure phase of a baroclinic wave. The radiatively clear state has clouds that are too tenuous when surface based or, irrespective of opacity, located too far aloft to contribute significantly to the surface energy budget. There is a 13-K surface temperature difference between the two states, and atmospheric inversion peak temperatures are linearly related to the surface temperature in both states. The snow–sea ice interface temperature oscillates over the course of the winter season, as it cools during the radiatively clear state and is warmed from atmospheric emission above and ocean heat conduction from below during the opaquely cloudy state. Analysis of satellite data over the Arctic from 70°–90°N indicates that the radiatively clear and opaquely cloudy states observed at SHEBA may be representative of the entire Arctic basin. The results suggest that model formulation inadequacies should be easier to diagnose if modeled energy transfers are compared with observations using process-based metrics that acknowledge the bimodal nature of the Arctic ocean–ice–snow–atmosphere column, rather than monthly and regionally averaged quantities. Climate change projections of thinner Arctic sea ice and larger advective water vapor influxes into the Arctic could yield different frequencies of occupation of the radiatively clear and opaquely cloudy states and higher wintertime temperatures of SHEBA ocean, ice, snow, atmosphere, and clouds—in particular, a wintertime warming of the snow–sea ice interface temperature.

Developing an arctic subsistence observation system

The goal of the Arctic Observing Network Social Indicators Project subsistence component is to assess the adequacy of existing subsistence harvest data to advance our understanding of arctic change and to serve as the basis for recommending steps that can improve the observation network. The assessment is based on a database developed to include 1521 place/year records for Alaska and northern Canada. Of these records, 641 include estimates of harvest of all resources. Separate harvest reports are available for 131 species. Annual harvests are expressed as kilograms of edible harvest per capita for years ranging from 1965 to 2007. One or more measures per decade of comprehensive harvest in the 1990s and 2000s exist for 50 of the 411 arctic North American communities. Based on these results, in most, but not all regions, available data on subsistence harvests in Arctic North America cannot support analysis of changes in harvest over time. The Alaska Department of Fish and Game Community Subsistence Information System continues to provide harvest data for communities and has developed several regional sets of community harvest data in response to actual and potential environmental changes. The past harvest surveys conducted in the Nunavik, Inuvialuit, and Nunavut regions offer valuable experience as well as baseline data. The Arctic Borderlands Ecological Cooperative is a model of community–researcher collaboration. These past and current initiatives provide a foundation for the design of an expanded arctic subsistence observation network. The paper concludes with a discussion of challenges and recommendations.

Next steps toward an Arctic human dimensions observing system

The goal of The Arctic Observing Network Social Indicators Project (AON-SIP) was to develop a system of social observations that can answer the question, ‘Is the arctic system moving to a new state?’ Much of the project effort focused on compiling data on human activities in the arctic that might interact with climate change and social indicators of arctic well-being. This paper reviews the adequacy of the data analyzed in the project for three objectives: observing changes in well-being of arctic residents, observing arctic changes relevant to global society, and understanding ongoing social change in the arctic. The review highlights issues of comparability of data across different scales in different nations, as well as key observation gaps. Understanding change in well-being of arctic residents also requires observing additional less-climate-related drivers of change that the AON-SIP did not address, many of which also suffer from the same issues of comparability and data gaps. Two types of recommendations are offered for developing the arctic social observation system: (1) recommendations through the Arctic Council to national statistical agencies to achieve internationally comparable data, and (2) recommendations for essential new primary data collection.

Arctic Observing Network Social Indicators Project: overview

The Arctic Observing Network Social Indicators Project (NSF OPP0638408) is intended to contribute to the development of the Arctic Observation Network and to the science goals of SEARCH in two ways: (1) develop and make available to the science community relevant datasets and (2) identify gaps in the existing observation system and recommend appropriate actions to fill those gaps. The SEARCH Implementation Plan identified the following arenas of human activity likely to involve climate–human interactions: (1) subsistence hunting; (2) tourism; (3) resource development and marine transportation; and (4) commercial fishing. This project seeks to develop and assess datasets in these four areas. Again drawing from the SEARCH Implementation Plan priorities, the project also seeks to develop and assess datasets measuring social outcomes. This special issue of Polar Geography contains articles on each of the four arenas of human activity likely to involve climate–human interactions, an article on demographic indicators of social outcomes, an overview article, and a synthesis of recommendations for researchers and statistical agencies. The articles also introduce datasets now available to the research community.

Linking pan-Arctic human and physical data

The Arctic Observing Network–Social Indicators (AON-SI) project, building upon earlier work, developed an approach for linking social with physical science data across the Northern pan-Arctic. The first iteration of social data involves time series of demographic indicators in more than 100 separate regions, such as boroughs of Alaska, census divisions of Northern Canada, and oblast or autonomous regions of Northern Russia. Its geographical scope covers all of Alaska, Greenland, Iceland, the Faroe Islands, Norway, Sweden, and Finland, along with Northern parts of Canada and Russia. Administrative subdivisions within these areas define the regions. Key features of this data framework are (1) the list of region names, (2) a unified system of numerical identification codes, and (3) a region-year organization. We approximated the geographical area of each region as a particular set of 25 × 25 km grid cells, following the Equal-Area Scalable Earth Grid (EASE-Grid) scheme widely used in high-latitude natural science. Physical data in this format are accessible through the Arctic RIMS website. The linkage opens doors for integrated analysis of social and natural-science data, as illustrated by an analysis of Alaska community electricity use. Current versions of the database are published online.

Arctic observing network social indicators and northern commercial fisheries

This article presents issues and challenges associated with collecting social indicator data in the context of northern commercial fisheries. The Arctic Observing Network Social Indicators Project (AON-SIP) fisheries domain database consists of geo-coded social indicator datasets from Alaska, Iceland, Norway, and Chukotka, of place/year catch, landings, employment, and permit data from 1980-present for commercially important species above 60°N and in the Bering Sea. Comparability of indicator data across regions will be important for the future monitoring and modeling of the effects of changes in the arctic environment such as those influenced by diminishing sea ice cover and increasing ocean acidification which will impact fisheries production and distribution. Equally important, the collection and analysis of time-series social indicator data could aid in understanding how arctic residents experience the processes of globalization as they participate in industries such as fisheries that are increasingly dominated by non-local corporations. Because of this extrinsic control of resources, social indicator data reflecting local ownership in fisheries rights and revenues could be functional in understanding how changes in fisheries impact arctic livelihoods. It is also necessary to understand how changes in fisheries fit within a broader resource use and arctic development context, for example, in conjunction with the oil and gas industry. Finally, planning for arctic fisheries of the future will be dependent upon data collection and analysis activities that can inform management plans and governance structures accommodating international boundary conflicts, rights-based management regimes, indigenous access, and organization/oversight of arctic marine science initiatives.

Environmental, Geopolitical Change in the Arctic

With climate change rapidly transforming environmental and geopolitical conditions in the Arctic region, scientists and policy makers are calling for improved science observation capabilities and more attention to the region.“We do not have a satisfactory observational capability in the Arctic, on the ground, using aircraft, or using satellites and spaceborne instruments,” said Martin Jeffries, program director of the Arctic Observing Network in the U.S. National Science Foundation's (NSF) Office of Polar Programs. He was one of the speakers at the 9 June Forum on Earth Observations IV, held in Washington, D.C. He noted that many U.S. federal agencies are engaged in data gathering and that NSF is working with some agencies to develop an interagency Arctic observing network.

Saon

Sustaining Arctic Observing Networks (SAON) is a process to support and strengthen the development of multinational engagement for sustained and coordinated pan-Arctic observing and data sharing systems that serve societal needs, particularly related to environmental, social, health, economic and cultural issues.

Sea-Ice System Services: A Framework to Help Identify and Meet Information Needs Relevant for Observing Networks

The need for data from an Arctic observing network to help stakeholders with planning and action is generally recognized. Two key research concerns arise: (1) potential contrasts between fundamental and applied science in the design of an observing system, and (2) development of best practices to ensure that stakeholder needs both inform and can be met from such an observing system. We propose a framework based on the concept of sea-ice system services (SISS) to meet these challenges and categorize the ways in which stakeholders perceive, measure, and use sea ice. Principal service categories are (1) climate regulator, marine hazard, and coastal buffer; (2) transportation and use as a platform; (3) cultural services obtained from the “icescape”; and (4) support of food webs and biological diversity. Our research focuses on cases of ice as platform and marine hazard in Arctic Alaska. We identify the information for each SISS category that users need to track, forecast, and adapt to changes. The resulting framework can address multiple information needs and priorities, integrate information over the relevant spatio-temporal scales, and provide an interface with local knowledge. To plan for an integrated Arctic Observing Network, we recommend a consortium-based approach with the academic community as an impartial intermediary that uses the SISS concept to identify common priorities across the range of sea-ice users.

Automated Ice-Tethered Profilers for Seawater Observations under Pack Ice in All Seasons

Abstract An automated, easily deployed Ice-Tethered Profiler (ITP) instrument system, developed for deployment on perennial sea ice in the polar oceans to measure changes in upper ocean water properties in all seasons, is described, and representative data from prototype instruments are presented. The ITP instrument consists of three components: a surface subsystem that sits atop an ice floe; a weighted, plastic-jacketed wire-rope tether of arbitrary length (up to 800 m) suspended from the surface element; and an instrumented underwater unit that employs a traction drive to profile up and down the wire tether. ITPs profile the water column at a programmed sampling interval; after each profile, the underwater unit transfers two files holding oceanographic and engineering data to the surface unit using an inductive modem and from the surface instrument to a shore-based data server using an Iridium transmitter. The surface instrument also accumulates battery voltage readings, buoy temperature data, and locations from a GPS receiver at a specified interval (usually every hour) and transmits those data daily. Oceanographic and engineering data are processed, displayed, and made available in near–real time (available online at http://www.whoi.edu/itp). Six ITPs were deployed in the Arctic Ocean between 2004 and 2006 in the Beaufort gyre with various programmed sampling schedules of two to six one-way traverses per day between 10- and 750–760-m depth, providing more than 5300 profiles in all seasons (as of July 2007). The acquired CTD profile data document interesting spatial variations in the major water masses of the Canada Basin, show the double-diffusive thermohaline staircase that lies above the warm, salty Atlantic layer, measure seasonal surface mixed layer deepening, and document several mesoscale eddies. Augmenting the systems already deployed and to replace expiring systems, an international array of more than one dozen ITPs will be deployed as part of the Arctic Observing Network during the International Polar Year (IPY) period (2007–08) holding promise for more valuable real-time upper ocean observations for operational needs, to support studies of ocean processes, and to facilitate numerical model initialization and validation.

Sustained Arctic Observations: A Legacy of the Polar Year

Is the Arctic a vast, beautiful, wild, and unsullied natural refuge, or is it small, fragile, and vulnerable, suffering the brunt of global warming? In the late nineteenth century, as U.S. admiral Robert E. Peary and his competitors engaged in their mad scramble to be the first humans to set foot on the North Pole, “fragile” was unlikely to be an adjective that sprang to mind when they described their surroundings. Quite the opposite, exploring the Arctic exposed the fragility of man. But the Arctic Ocean and mankind's relationships to it are changing fast.

Development of a Pan‐Arctic Database for River Chemistry

More than 10% of all continental runoff flows into the Arctic Ocean. This runoff is a dominant feature of the Arctic Ocean with respect to water column structure and circulation. Yet understanding of the chemical characteristics of runoff from the pan‐Arctic watershed is surprisingly limited. The Pan‐ Arctic River Transport of Nutrients, Organic Matter, and Suspended Sediments ( PARTNERS) project was initiated in 2002 to help remedy this deficit, and an extraordinary data set has emerged over the past few years as a result of the effort. This data set is publicly available through the Cooperative Arctic Data and Information Service (CADIS) of the Arctic Observing Network (AON). Details about data access are provided below.

Acoustic navigation and communications for high latitude ocean research (ANCHOR)

Recent community reports on autonomous and Lagrangian platforms and Arctic observing identify the development of under-ice navigation and telemetry technologies as one of the critical factors limiting the scope of autonomous (e.g. floats, AUVs and gliders) high-latitude measurement efforts. These platforms could provide persistent, high-resolution, basin-wide sampling in ice-covered regions and collect measurements near the critical ice-water interface. Motivated by the dramatic advances in temporal and spatial reach promised by autonomous sampling and by the need to coordinate nascent efforts to develop navigation and communication system components, an international group of acousticians, platform developers, high-latitude oceanographers and marine mammal researchers gathered in Seattle, U.S.A. from 27 February - 1 March for an NSF Office of Polar Programs sponsored Acoustic Navigation and Communication for High-latitude Ocean Research workshop. Workshop participants summarized the current state of knowledge concerning Arctic acoustics, navigation and communications, developed an overarching system specification to guide community-wide engineering efforts and established an active community and steering group to guide long-term efforts and ensure interoperability between elements developed by disparate teams. This presentation will summarize workshop findings and provide an update on recent developments stemming from the EU DAMOCLES and US NSF Arctic Observing Network programs.

The gravitational effect of ocean tide loading at high latitude coastal stations in Norway

Gravity measurements close to the ocean are strongly affected by ocean tide loading (OTL). The gravitational OTL effect consists of three parts, i.e. a change in gravity caused by direct attraction from the variable water-masses, by displacement of the observing point due to the load, and by redistribution of masses due to crustal deformation. We compare the OTL gravitational effect of several global models to observed time-series of gravity to identify the best model for four arctic observation sites. We also investigate if the global models are sufficient for correcting gravity observations. The NAO99b model fits the observations best at three stations. At two stations (Tromso and Bodo) the global models explain the variability in the observations well. At the other two (Honningsvag and Andoya), a significant periodic signal remains after the OTL correction has been applied. We separate two of the gravitational effects, the direct attraction and the change in gravity due to displacement, to study the local effects. Simple geometric models of the water load and independent measurements from local tide-gauges are used to calculate these effects. This leads to improved correspondence with the OTL signal, hence demonstrating the importance of careful modelling of local effects for correction of gravity observations in coastal stations.