An Introduction to NASA's ARCSIX Campaign

Introduction

ARCSIX Campaign Overview and Study Region

In many ways, sea ice is the heart of the Arctic system. It serves as a "middleman" that modulates the flow of energy between the atmosphere and ocean. Over the last 40 years, we have watched the Arctic sea ice pack transform from a thick, multi-year ice pack to a predominately thin, seasonal ice pack. This transformation in Arctic sea ice is not only impacting the Arctic, but is sending ripples across the globe. The rapid change in Arctic sea ice is driving an increased demand for accurate Arctic forecasts to support the economic competition in the region. The value of Arctic predictions will continue to grow. While the existence of Arctic change is clear, predictions differ on the expected pace of sea ice decline over the next few decades and beyond. The source of this uncertainty lies in our understanding of the interactions between the atmosphere and the surface, the cloud lifecycle, and the aerosol properties and chemistry in the Arctic. An improved understanding of the processes contributing to this change is needed to advance prediction capabilities. NASA's Arctic Radiation-Cloud-aerosol-Surface Interaction eXperiment (ARCSIX) field campaign was designed to collect critical data on clouds, radiation, sea ice, and aerosols.

ARCSIX took place over approximately 8 weeks between May and August 2024. The campaign was based at Greenland's Pituffik Space Base and consisted of two field deployments: May 24 to June 16, 2024 (Spring), and July 22 to August 16, 2024 (Summer). These two periods were selected to bookend the sea ice melt season and capture the changes in sea ice properties and the factors that contributed to summer melt. These data provide unique test cases for model predictions of melt and the ability to track sea ice melt processes from space. ARCSIX generated a unique data set characterizing the sea ice, radiation, cloud, and aerosol conditions during the 2024 summer melt season over the sea ice north of Greenland. The ARCSIX data set will be used for decades to understand the drivers of Arctic sea ice melt.

Science Objectives

ARCSIX science is guided by three broad science questions that encapsulate the key influences of radiation-cloud-aerosol-sea ice coupling and a remote sensing and modeling objective:

Science Question 1 (Radiation): What is the impact of the predominant summer Arctic cloud types on the radiative surface energy budget? Science Question 2 (Cloud Life Cycle): What processes control the evolution and maintenance of the predominant cloud regimes in the summertime Arctic? Science Question 3 (Sea Ice): How do the two-way interactions between surface properties and atmospheric forcings affect the sea ice evolution? Remote Sensing and Modeling Objective: Enhance our long-term space-based monitoring and predictive capabilities of Arctic sea ice, clouds, and aerosols.

Measurements

ARCSIX data were collected from three aircraft (NASA P-3B, NASA G-III, and the Stratton Park Engineering Company (SPEC) Lear Jet) and a sea ice buoy array, each with a unique role. The G-III - the high-flyer - served as a bridge to satellite observations by surveying the surface and atmospheric properties with remote sensing instruments from above while the P-3B - the low-flyer - acquired in situ, aerosol, cloud, atmospheric characteristics, and surface properties along with radiation below, above, and inside cloud layers. The SPEC Lear Jet - also a low-flyer - carried a full suite of cloud microphysical measurements and a newly-developed Ka-band cloud radar enabling simultaneous multi-level in situ cloud and aerosol sampling. The sea ice mass balance buoy array was deployed ~1 month before the field deployment by the Cold Regions Research and Engineering Laboratory (CRREL) and University of Dartmouth providing data to track the sea ice floe and its evolution. The P-3B and G-III participated in both campaigns and were joined by the SPEC Lear Jet in summer. A hallmark of the ARCSIX data set is the high level of successful coordination of aircraft sampling.

NASA P-3B

The P-3B carried a comprehensive instrument payload to characterize atmospheric state, radiation, surface properties, trace gases, aerosols, and clouds. This included a blend of in situ and remote sensing instruments. The P-3B instrumentation included a diode laser hygrometer (DLH; both a standard and short path package), the Turbulent Air Motion Measurement System (TAMMS), the Multi-functional Airborne Raman Lidar (MARLi), the 5-beam Airborne Doppler Radar (ADL), Solar Spectral Flux Radiometer (SSFR) radiation suite, Broadband Ratiometer (BBR) radiation suite, KT19, Land Vegetation, and Ice Sensor (LVIS) lidar and camera suite, the Research Scanning Polarimeter (RSP), a G2401 Picarro measuring CO, CO ₂ , and CH ₄  trace gases, the Langley Aerosol Research Group Experiment (LARGE) instrument suite measuring aerosol size distribution and optical properties, the Aircraft Aerosol Time-of-Flight Mass Spectrometer (A-ATOFMS), the Differential Aerosol Sizing and Hygroscopicity Spectrometer Probe (DASH-SP), the Continuous Flow Diffusion Chamber 1H (CFDC-1H) and Ice Spectrometer to measure ice nucleating particle concentrations. A complete suite of Stratton Park Engineering Company (SPEC) cloud microphysical probes were also flown on the P-3B to measure the complete cloud particle size distribution, including the Fast Two-Dimensional-Gray probe (2D-Gray), Two-Dimensional Stereo (2D-S) probe with horizontal and vertical arms, Fast Cloud Droplet Probe (FCDP), a High-Volume Precipitation Spectrometer (HVPS-4), a Particle Phase Spectrometer (PPS), and Hawkeye Combination Cloud Particle Probe. The flights were generally 6-8 hours long, reaching altitudes as high as 22,000 ft and with careful coordination with the higher-flying G-III aircraft.

NASA G-III

The NASA C-20B Gulfstream III (G-III) aircraft was used as the high-flying platform to provide large-scale context and vertical profile information. The G-III was often in close coordination with the P-3B. The G-III payload consisted of the High-Altitude Lidar Observatory (HALO), the Airborne Visible InfraRed Imaging Spectrometer-Next Generation (AVIRIS-NG) imager, and the Airborne Vertical Atmospheric Profile System (AVAPS) dropsonde system. HALO was operated in the water vapor/aerosol/cloud configuration during ARCSIX. AVIRIS-NG is a push broom spectral mapping system with high signal-to-noise ratio, designed and toleranced for high-performance spectroscopy with a wavelength range of 380 to 2510nm. Dropsondes were routinely deployed from the G-III.

SPEC Lear Jet

The SPEC Lear Jet 35 instrument payload complements the other aircraft mostly focusing on detailed cloud data as summarized below. The Lear Jet had an M300 Series data aquisition system that obtained navigational and atmospheric state data, including latitude/longitude, altitude, aircraft heading and total air speed, temperature, dew point temperature, static pressure, icing rod frequency, and 3-D winds. The cloud microphysical probes used were essentially identical to those deployed on the P-3B. A unique instrument on this platform was the ProSensing Ka-Band Probe Radar-Radiometer (KPR), which provides upward and downward looking vertical profiles of radar reflectivity and Doppler velocity providing additional data on cloud processes.

Sea Ice Mass Balance Buoys

The sea ice buoy array was comprised of nine sea ice mass balance buoys (SIMB-3; Polashenski et al., 2011; Planck et al., 2019) deployed in the Lincoln Sea ~1 month before ARCSIX began. The map shows the initial position and drift track of each buoy within the array. For the campaign most of the buoys drifted slowly westward and/or towards the northern coast of Greenland. Buoy J was the exception and drifted quickly towards the east. Buoy position was determined and logged using GPS and communicating with the Iridium constellation. Each buoy contains a downward facing acoustic rangefinder mounted to the buoy top to measure position above the sea ice surface, and an upward facing acoustic rangefinder mounted to the buoy under the sea ice to measure ice bottom position, downwelling and upwelling shortwave radiation, a barometric pressure sensor, air temperature sensor, and a digital temperature string that extended to ~60 cm deep into the sea ice. The initial snow depth and ice thickness measurements were made at installation. Four of the buoys (L, O, P, R) included SnowTatos that measured temporal variations in snow depth. Watch a sea ice buoy being deployed in the video provided by CRREL.

Flight Summaries

ARCSIX conducted 44 total research flights across the two campaigns and three aircraft (P-3B: 19, G-III: 15, Learjet: 10). These visualizations show the flight tracks for each research flight separated into Spring and Summer. To measure the factors that were driving sea ice melt, we need measurements throughout the melt season. The spring campaign captures conditions before melt, providing a baseline. The summer campaign captures conditions after melt. Part of the data analysis is to compare the changes between the two periods.

The animations show that flight tracks can take on some interesting shapes. In fact, we did have some fun naming the flight track shapes including shipping boxes, salt water taffy, a snowman, and the one flight track even looked like a Halberd. Each of these flight tracks were designed with a specific science objective in mind. It is just a coincidence that they resulted in some amusing shapes. The research flight on 28 May 2024 was a survey of the region with sea ice buoys to provide a context of the Lincoln Sea ice conditions. The “H”- or “I-” shaped patterns consisted of two cloud walls where the P-3B and G-III were stacked on top of one another to characterize cloud evolution. The 31 May 20204 flight is an example of the bowling alley, where P-3B flew several low altitude legs to capture surface conditions and better determine how and in which directions the surface reflects sunlight. Above the P-3B, the G-III flew a lawnmower or Zamboni pattern of evenly spaced lines. In summer, the Learjet flight pattern primarily consisted a porpoising (or saw tooth) pattern, sampling from the top to the bottom of low altitude cloud layers.

Deployments: A Tale of Two Campaigns

A day in the life of ARCSIX

Pituffik Space Base is in the northwestern part of Greenland. It is extremely remote and was an ideal location for ARCSIX since it gave us access to the oldest sea ice in the Arctic; ice that is becoming increasingly rare. In most other places in the world, one could say that a typical day for ARCSIX began before daybreak, but the sun never set in Pituffik during ARCSIX. Our days began at 4am with a go-no/go decision meeting. In these meetings, we used the most up-to-date satellite images (often 2-3 hours old) and weather forecasts to decide which flight plan would provide us the most scientific value. When we decided to go, we started to prep the instruments and the aircraft. Some of the instruments needed ~3 hours to warm up and be ready to collect data.

After takeoff, we typically flew north and saw some amazing landscapes during the ~1.5 hour transit to sea ice. The flight in the video is from June 10, 2024, and involved both the P-3B and the NASA G-III. On each flight, the NASA P-3B carried about 20 scientists and 5 crew flying at altitudes ranging from 300 feet above the sea ice surface to 22,000 feet. The P-3B contained more than 20 instruments. The NASA G-III would take off between 15 minutes to an hour later. This was primarily because the G-III flies faster, so we staggered takeoff times so that the two aircraft could spend most of their time collocated, collecting measurements simultaneously. Those not flying were analyzing the weather forecast and preparing the flight plans for the next day. Once everyone arrived back home, we closed the day with a post flight briefing and discussed the possible plans for the next day. Those were full days. They were worth it. ARCSIX collected a treasure trove of new data that we are just beginning to scratch the surface.

A run down the Nares Strait

On the way home from the sea ice pack, we often flew in and around the Nares Strait. The Nares Strait is a small region of water and sea ice between Greenland and Canada. It was convenient that it was on our way home because it is a scientifically valuable target. The animation shows a video of a 1-hour P-3B flight down the Nares Strait and on the right shows the atmospheric chemistry, aerosol, and cloud data. The region is surrounded by higher elevations and the winds get funneled into the Strait and exceed 50 miles per hour on a regular basis. These high winds mean that aerosols can be strongly lofted in this region.

The first thing we found there was smoke from fires shown by the increasing green bars. Did you see the wiggle in the video? That was a calibration maneuver for the LVIS instrument that is used to measure sea ice thickness. This maneuver was to make sure that we understood how the instrument was aligned. Next, the gray line shows the P-3B descending into the boundary layer to sample air closer to the surface. The air in the lower atmosphere was marine influenced air, not smoke. Marine influenced air tends to be cleaner (fewer particles). The flight then ascended out of the boundary layer, back up to where the smoke was and found that it had dissipated. At the end of the flight, there were some clouds we encountered that were optically thin and in very clean conditions (low aerosols). This set of flights is going to be key to advancing our understanding of the important role that the Nares Strait plays in the region.

Outreach

Science Team Meetings

ARCSIX hosted its first post-campaign science team meeting from May 19-21, 2025, in Boulder, CO which included an open data workshop. During the data workshop, instrument teams explained how their instruments worked and the data they collected during ARCSIX (data workshop video here). During the rest of the meeting, the ARCSIX Science Team shared preliminary results and planned on the next steps to advance ARCSIX Science Goals.

Outreach Activities

During the ARCSIX campaign, the team held three events to engage with the local community at the Pituffik Space Force Base. Two of these events, one in the spring and one in the summer, were hangar open house events where we opened the door to the hangar and our aircraft for the local community to take a look and ask questions. During the spring campaign, the ARCSIX team also gave a public seminar at the Pituffik Community Center for people to come and hear about the science and ask questions.

Data Access

The Atmospheric Science Data Center (ASDC) at NASA Langley Research Center is responsible for the archival and distribution of ARCSIX data.