Climate is rapidly changing all over the globe, but nowhere is that change faster than in the Arctic. The evidence from recent years is clear: Reductions in sea ice [Kwok and Untersteiner, 2011] and permafrost [Romanovsky et al., 2002], in addition to modification of the terrestrial ecosystem through melting permafrost and shifting vegetation zones [Burek et al., 2008; Sturm et al., 2001], all point to a rapidly evolving Arctic climate.
However, the ability of numerical climate models to capture the dynamics of the Arctic still needs improvement. For example, several recent studies have demonstrated deficiencies in the representations of clouds in climate models [e.g., de Boer et al., 2012]. Models also struggle with simulating stable atmospheric boundary layers [e.g., Steeneveld et al., 2006], as well as simulating Arctic aerosol properties and their effects on how clouds alter the transfer of energy through the atmosphere [English et al., 2014].
To improve these models, scientists have started flying unmanned aerial systems (UAS)—commonly known as drones—and tethered balloon systems (TBS) to collect measurements of the atmosphere, cryosphere, ocean, and land surface. These platforms show great promise in collecting three-dimensional data sets at resolutions that climate scientists have never before been able to obtain.
However, to ensure public safety, the Federal Aviation Administration (FAA) currently limits general operations of these platforms, sometimes curtailing their utility for scientific research. To enable research on processes important to climate change in the Arctic—those involving aerosol particles, clouds, and the surface energy budget—the U.S. Department of Energy (DOE) supports the Oliktok Point measurement facility, which includes areas of special-use airspace that allow more flexible operations of UAS and TBS for Arctic climate research.
Located in the Prudhoe Bay oilfield region on Alaska’s North Slope, approximately 250 kilometers east-southeast of the town of Barrow, Oliktok Point provides exciting new opportunities to evaluate regional variability in the U.S. Arctic. These opportunities come not only from the added UAS capabilities but also from the fact that the DOE added an instrument observatory at Oliktok Point. This observatory expands upon DOE’s extensive previous efforts in this environment, including nearly 20 years of observations at Barrow, a shorter deployment at Atqasuk (90 kilometers south of Barrow), and numerous field campaigns.
Opening the Arctic Skies
DOE’s history at Oliktok Point started in 2004, when Sandia National Laboratories, through its involvement with the DOE Atmospheric Radiation Measurement (ARM) Climate Research Facility, worked with the FAA to develop an area of restricted airspace to support use of tethered balloon systems that observe the Arctic atmosphere. The area, designated R-2204, consists of a 4-nautical-mile-diameter cylinder centered on Oliktok Point and includes two height ranges, the first extending an elevation of 1500 feet and the second extending from 1500 to 7000 feet (see Figure 1, left; feet and nautical miles are the units the FAA uses when discussing airspace; 1 foot = 0.3 meter). That way, the entire air column does not need to be closed to outside air traffic when measurement activities are limited to low altitudes. Previously, this airspace hosted the ARM Mixed-Phase Arctic Clouds Experiment (M-PACE), which investigated cloud microphysics and radiative properties [Verlinde et al., 2007], but saw minimal use afterward.
Over the past decade, usage of drones and tethered balloons for scientific study has become increasingly popular as technology has come down in price. For example, Curry et al.  and Inoue et al.  led initial efforts to fly over the North Slope of Alaska. However, the increased popularity of drones resulted in new restrictions on where and when these platforms can be operated, limiting their usefulness for advancing science. To meet the growing demand for airspace, in 2009 DOE again worked with the FAA to indefinitely extend the availability of R-2204 for DOE-supported research activities and increase the number of available days from 30 to 75 per year.
Spurred by the rapid decline in Arctic sea ice and the need to better understand the evolving Arctic atmosphere and its interactions with the surface, the DOE further worked with the FAA to develop a new block of airspace for researchers to use, extending approximately 700 nautical miles over the Beaufort Sea to the north of Oliktok Point (see Figure 1, right). This space, designated warning area W-220, is 40 nautical miles wide and divided into two altitude ranges (0–2000 feet and 2000–10,000 feet) and will provide critical access for scientists to the environment overlying the Arctic Ocean.
Support on the Ground
To advance Arctic climate research, the DOE ARM Climate Research Facility has deployed a ground-based mobile research facility (AMF-3) to Oliktok Point, Alaska, until at least 2019. The facility is one of three that DOE operates and is equipped with a wide variety of instruments, including remote sensors for measuring cloud properties and energy transfer in the atmosphere (e.g., radars, laser-scanning lidar mapping, and radiometers), sensors for surface weather and airborne pollutants, and towers of instruments that measure the exchange of carbon and water vapor between the air and the ground.
When paired with this world-class surface observatory, unmanned aircraft and tethered balloons provide a unique asset not currently replicated anywhere else in the Arctic. For example, the combined effort can gather detailed profiles of atmospheric properties from the surface to 7000 feet in elevation, as well as information on spatial heterogeneities across a given elevation.
All measurements, along with a variety of official and user-produced data products, are available for download through the ARM Data Archive, providing easy access for the scientific community and general public. The Oliktok Point facility has also recently been integrated into the Arctic-wide International Arctic Systems for Observing the Atmosphere (IASOA) [Uttal et al., 2015] network, providing opportunities to further assess the spatial representativeness for the unique measurements obtained there.
Recent Flight Operations at Oliktok Point
Unmanned aircraft have flown several campaigns at Oliktok Point in recent years. In the summer of 2013, DOE worked with NASA, the National Oceanic and Atmospheric Administration, and the Office of Naval Research to carry out the Marginal Ice Zone Experiment to study the physics of the transition region between frozen sea and open water—a crucial element of climate models in the Arctic.
During this campaign, several different unmanned aircraft flew within and outside of R-2204, including flights into the surrounding international airspace. These aircraft collected atmospheric measurements and dropped small buoy systems into the sea to make in situ observations of the upper ocean along the ice water interface at the edge of the pack ice. During October of 2014, DOE worked with the University of Colorado and Penn State University to carry out the Coordinated Observations of the Lower Arctic Atmosphere (COALA) exercise to make detailed measurements of lower atmospheric thermodynamic variables during the time of sea ice formation offshore. This exercise featured both unmanned aircraft and tethered balloon flights within R-2204.
Flight activities were expanded in 2015, including the DOE-funded Evaluation of Routine Atmospheric Sounding Measurements using Unmanned Systems (ERASMUS) campaign, the U.S. Coast Guard Arctic Shield 2015 rescue training operations, additional tethered balloon flights, and the ARM Airborne Carbon Measurements (ACME-V) campaign. The latter used both W-220 and R-2204 to complete low-altitude flights using a DOE-supported twin turboprop manned research plane [Schmid et al., 2014]. ERASMUS flights targeted routine profiling of the lower Arctic atmosphere (up to 7000 feet) and measurements to understand the interactions between thermodynamic structure and cloud formation. ACME-V flights, although focused on observing atmospheric gas fluxes and transport, also featured a robust set of instrumentation to improve understanding of Arctic cloud and aerosol properties.
To take advantage of the airspace at Oliktok Point, ARM is bolstering its drone and tethered balloon programs with a variety of new aircraft and instruments that will begin flying in 2016. Sandia National Laboratories, which manages the ARM measurement sites on Alaska’s North Slope, already operates a variety of tethered balloon systems at Oliktok Point and has expanded their capabilities through a variety of miniaturized atmospheric instruments. For both UAS and TBS, this expanded effort will include sensors to measure clouds, aerosols, radiation, thermodynamics, and surface properties. ARM plans to operate these craft in both routine and focused campaign environments at Oliktok Point over the coming years.
Measurements from these platforms will be made available to the international research community through the ARM Data Archive, alongside measurements from other ARM facilities, including the Oliktok-deployed AMF-3 and the Barrow site. In addition, the airspace will be available for the scientific community to propose investigator-based UAS operations as part of ARM-sponsored field campaigns.