Stephen F. Ackley

Stephen F. Ackley
University of Texas at San Antonio | UTSA · Department of Geological Sciences

About

210
Publications
19,630
Reads
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8,297
Citations
Additional affiliations
January 2001 - March 2006
Clarkson University
Position
  • Professor
June 1968 - January 1999
Cold Regions Research and Engineering Lab (CRREL)
Position
  • Sr. Res Geophysicist

Publications

Publications (210)
Conference Paper
Antarctic coastal polynyas have been coined as "ice factories" because of the high ice formation rates under the influence of cold katabatic winds from the Antarctic continent. Ice forms at high rates in the open water areas created by the wind-blown advection of the new ice formed. During the May 2017 PIPERS cruise into Terra Nova Bay (TNB) in the...
Conference Paper
The presence of microplastics (MPs) in ecosystems across the globe is thought to be partly due to atmospheric transport and have been projected to operate differently as either wet or dry deposition. Yet understanding of how MPs behave and interact in the atmosphere is still in its infancy. There is a lack of data in identifying whether atmospheric...
Article
The fine spatial resolution of the ICESat-2 (IS2) satellite altimeter allows monitoring the evolution of sea ice thickness with detailed dynamic information (e.g. ridges and leads). In this study, we first assess the ability of IS2 to estimate thermodynamic ice growth and dynamic thickening during the ice-growing season in the central Arctic Ocean....
Article
Full-text available
Sentinel-1 C-band synthetic aperture radar (SAR) images can be used to observe the drift of icebergs over the Southern Ocean with around 1-3 d of temporal resolution and 10-40 m of spatial resolution. The Google Earth Engine (GEE) cloud-based platform allows processing of a large quantity of Sentinel-1 images, saving time and computational resource...
Preprint
Full-text available
Polynyas are key sites of ice production during the winter and are important sites of biological activity and carbon sequestration during the summer. The Amundsen Sea Polynya (ASP) is the fourth largest Antarctic polynya, has recorded the highest primary productivity and lies in an embayment of key oceanographic significance. However, knowledge of...
Article
Full-text available
NASA’s ICESat-2 has been providing sea ice freeboard measurements across the polar regions since October 2018. In spite of the outstanding spatial resolution and precision of ICESat-2, the spatial sparsity of the data can be a critical issue for sea ice monitoring. This study employs a geostatistical approach (i.e., ordinary kriging) to characteriz...
Preprint
Full-text available
Sentinel-1 C-band synthetic aperture radar (SAR) images can be used to observe the drift of icebergs over the Southern Ocean with around 1–3 days of temporal resolution and 10–40 m of spatial resolution. The Google Earth Engine (GEE) cloud-based platform allows processing of a large quantity of Sentinel-1 images, saving time and computational resou...
Article
Full-text available
The measurement of sea ice elevation above sea level or the “freeboard” depends upon an accurate retrieval of the local sea level. The local sea level has been previously retrieved from altimetry data alone by the lowest elevation method, where the percentage of the lowest elevations over a particular segment length scale was used. Here, we provide...
Article
Full-text available
As part of the Polynyas and Ice Production in the Ross Sea (PIPERS) project, the IcePod system onboard the LC-130 aircraft based at McMurdo Station was flown over the Ross Sea, Antarctica in November 2016 and 2017, with the purpose of repeating the same lines that NASA’s Operation IceBridge (OIB) aircraft flew over in 2013. We resampled the lidar d...
Article
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The changing distributions of sea ice thickness in different regions around Antarctica are important metrics of climate variability, but estimates have large uncertainties. Here, we analyze laser altimetry data from ICESat and IceBridge to generate a record of total freeboard and sea ice thickness in the Amundsen‐Bellingshausen and Weddell seas dur...
Article
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High sea ice production (SIP) generates high-salinity water, thus, influencing the global thermohaline circulation. Estimation from passive microwave data and heat flux models have indicated that the Ross Ice Shelf polynya (RISP) may be the highest SIP region in the Southern Oceans. However, the coarse spatial resolution of passive microwave data l...
Article
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NASA's Operation IceBridge mission flew over the Ross Sea, Antarctica (20 and 27 November 2013) and collected data with Airborne Topographic Mapper (ATM) and Digital Mapping System (DMS). Using the DMS and reflectivity of ATM L1B, leads are detected to define local sea level height. The total freeboard is then obtained and converted to ice thicknes...
Poster
Full-text available
High sea ice production (SIP) causes high-salinity water formation, influencing the global thermohaline circulation. Based on passive microwave data and a heat flux model, the Ross Ice Shelf polynya (RISP) region has been reported as the highest SIP region in the Southern Ocean. However, there are two limitations in previous methods: (1) the coarse...
Article
This paper presents a wave-in-ice model calibration study. Data used were collected in the thin ice of the advancing autumn marginal ice zone of the western Arctic Ocean in 2015, where pancake ice was found to be prevalent. Multiple buoys were deployed in seven wave experiments; data from four of these experiments are used in the present study. Wav...
Article
Full-text available
Antarctic pack ice is inhabited by a diverse and active microbial community reliant on nutrients for growth. Seeking patterns and overlooked processes, we performed a large-scale compilation of macro-nutrient data (hereafter termed nutrients) in Antarctic pack ice (306 ice-cores collected from 19 research cruises). Dissolved inorganic nitrogen and...
Article
Full-text available
Antarctic pack ice is inhabited by a diverse and active microbial community reliant on nutrients for growth. Seeking patterns and overlooked processes, we performed a large-scale compilation of macro-nutrient data (hereafter termed nutrients) in Antarctic pack ice (306 ice-cores collected from 19 research cruises). Dissolved inorganic nitrogen and...
Article
The existence and detection of leads are critical to obtain a local Sea Surface Height (SSH) reference for computing total freeboard and sea ice thickness from NASA's IceBridge Airborne Topographic Mapper (ATM) elevations. However, the shaded areas of the Digital Mapping System (DMS) images and the biased ATM elevations impact the correct determina...
Article
Full-text available
The Antarctic Roadmap Challenges (ARC) project identified critical requirements to deliver high priority Antarctic research in the 21st century. The ARC project addressed the challenges of enabling technologies, facilitating access, providing logistics and infrastructure, and capitalizing on international co-operation. Technological requirements in...
Article
Full-text available
Temporal changes in the concentration profiles of dimethylsulfide (DMS), dimethylsulfoniopropionate (DMSP), and dimethylsulfoxide (DMSO) were measured in pack ice from the Bellingshausen Sea (Antarctica) during the winter-spring transition of 2007. Two sites with contrasting snow and ice thicknesses were sampled, with high concentrations of DMS, DM...
Article
High-spatial-resolution aerial photographs can provide detailed distribution of sea ice features. However, very few studies have ever considered shadows on the photographs for sea ice detection. In this letter, sea ice shadows, retrieved from 163 selected aerial photographs acquired on July 26, 2010, in a marginal-ice-zone area near Barrow, Alaska,...
Article
Knowledge of Arctic snow and ice surface albedo is essential to understand local energy budget and snow/ice albedo feedback under global warming scenario. In situ measured albedo plays an essential role by providing ground truth reference for remote sensing monitoring of albedo at large scale. Such measurements with portable and fixed-location spec...
Article
This study was conducted to estimate the potential for natural iron fertilization in the Bellingshausen Sea, a remote region in the Pacific sector of the Southern Ocean. Seawater samples were collected during early austral spring 2007 near the continental margin, in the wake of an iceberg and near Peter I Island in order to identify and quantify Fe...
Conference Paper
Full-text available
We present a large collaborative program investigating surface processes over the Arctic Ocean during the early autumn ice advance. With recent observed and predicted declines in summer minimum sea ice extent, the nature and role of air-ice-waves-ocean interactions driving autumn ice advance are expected to change. Central to these changes, the gre...
Article
Full-text available
We examine the role of ocean heat flux (OHF) in Antarctic sea-ice growth and melt using data from autonomous ice mass-balance buoys deployed on pack ice in the Bellingshausen Sea and on fast ice in the Amundsen Sea during the spring/summer (October-December 2007) and summer/autumn (February-March 2009) transitions, respectively. OHFs are derived us...
Article
Full-text available
Temporal evolution of pCO 2 profiles in sea ice in the Bellingshausen Sea, Antarctica, in October 2007 shows physical and thermodynamic processes controls the CO 2 sys-tem in the ice. During the survey, cyclical warming and cool-ing strongly influenced the physical, chemical, and thermo-dynamic properties of the ice cover. Two sampling sites with c...
Article
Full-text available
Temporal evolution of pCO2 profiles in sea ice in the Bellingshausen Sea, Antarctica, in October 2007 shows that the CO2 system in the ice was primarily controlled by physical and thermodynamic processes. During the survey, a succession of warming and cold events strongly influenced the physical, chemical and thermodynamic properties of the ice cov...
Article
Full-text available
The Office of Naval Research initiated a Department Research Initiative (DRI) titled Sea State and Boundary Layer Physics of the Emerging Arctic Ocean. The central hypothesis of the 'Sea State' DRI is that surface waves now have a much greater role in the contemporary Arctic Ocean. Indeed, the entire Arctic Ocean in summer may soon resemble a margi...
Article
In situ measurements of sea ice thickness (I), snow depth (S), and snow freeboard (Fsn) from drilling profile lines from 15 cruises into the Southern Ocean, Antarctica, were analyzed. I was calculated from in situ Fsn and S using an isostatic approach. I was also directly estimated from Fsn as can be obtained from laser altimetry. The root-mean-squ...
Article
Full-text available
In the summer of 2010, atmosphere–ice–ocean interaction was studied aboard the icebreaker R/V Xuelong during the Chinese National Arctic Research Expedition (CHINARE), in the sea ice zone of the Pacific Arctic sector between 150° W and 180° W up to 88.5° N. The expedition lasted from 21 July to 28 August and comprised of ice observations and measur...
Conference Paper
Sea ice is an important component of the Earth’s cryosphere. Observed and expected changes in the Earth’s climate system at the high latitudes are found to be partly linked to changes in the sea ice cover. The main characteristics describing the sea ice cover are A) the sea ice area fraction, B) the sea ice thickness, C) the sea ice motion, D) the...
Conference Paper
Full-text available
A collaborative effort between the University of Delaware (UD) and National Ice Center (NIC) addresses the need to provide open-source translations of sea ice stage-of-development into level ice thickness estimates on the 4km grid for the Interactive Multisensor Snow and Ice Mapping System (IMS). The characteristics for stage-of-development are qua...
Article
Sea ice thicknesses derived from NASA's Ice, Cloud, and Land Elevation Satellite (ICESat) altimetry data are examined using two different approaches, buoyancy and empirical equations, and at two spatial scales—ICESat footprint size (70 m diameter spot) and Advanced Microwave Scanning Radiometer (AMSR-E) pixel size (12.5 km by 12.5 km) for the Belli...
Article
Full-text available
The NASA IceBridge flights have obtained critical observations for Earth's polar ice since ICESat stopped collecting data in 2009. This study develops an automatic method in processing IceBridge Airborne Topographic Mapper (ATM) altimeter L1B data (one elevation per 3–4 m horizontally) to derive a local sea level height for referencing snow freeboa...
Article
Full-text available
As the world's ice diminishes in the face of climate change-from the dramatic decline in Arctic sea ice, to thinning at the margins of both the Greenland and Antarctic ice sheets, to retreating mountain glaciers the world over-Antarctic sea ice presents something of a paradox. The trend in total sea ice extent in the Antarctic has remained steady,...
Article
The Chinese National Arctic Research Expedition (CHINARE) in the summer 2010, primarily from 21 July to 28 August, in the ice zone of Arctic Pacific Sector, between 150° W to 180° W to 88.5° N, conducted comprehensive scientific studies on atmosphere-ice-ocean interactions, using icebreaker R.V. Xuelong. Measurements made included underway visual o...
Article
We made backscatter measurements at C band (5.3 GHz) over sea ice in the Weddell Sea. These measurements were performed from the German research vessel F.S. Polarstem during September and October, 1989. We acquired data on First-Year (FY) and Second-Year (SY) snow-covered sea ice at stations where the ship stopped and detailed snow and ice characte...
Article
Two ice mass balance buoys were deployed on the Amundsen Sea, Antarctica, ice pack near January 1, 2011. Below freezing air and snow temperatures and sea ice and seawater temperatures at the freezing point at this time indicated that summer melt had not yet commenced. Over the next two months, however, while snow depths changed by less than 0.1m, i...
Conference Paper
Sea ice is an important component of the climate system affecting ocean-atmospheric interactions and global energy balance. The assessment of sea ice thickness using satellite and airborne laser altimetry is largely dependent upon isostatic buoyancy relationships between snow, ice, slush and ocean water. The use of these relationships in estimating...
Article
ASPeCt ice observations, obtained during two cruises (JC Ross, Nov 2010 and Oden Dec 2010-Jan 2011) was compared to ENVIsat ASAR WSM satellite imagery over cruise areas in the Bellingshausen and Amundsen Seas. This comparison was performed to determine the ability to accurately interpret ENVIsat imagery, particularly for distinguishing first year a...
Article
Sea ice frequently forms in wavy waters. Wave motion packs forming ice crystals into small floes, while the ice attenuates the waves as the ice floes increase in diameter and thickness. Swell has been reported up to a few hundred kilometres inside the ice pack. Because of ocean waves, young ice floes take a rounded shape that led hungry early explo...
Conference Paper
Sea ice is a critical component of the Earth's climate system and is a highly complex media. The physical characteristics are important in interpretation of remote sensing data. Sea ice characteristics such as snow surface topography, snow depth and ice thickness were derived from in situ measurements obtained during the J.C. Ross (ICEBell) and Ode...
Article
Air and space campaigns such as IceSAT, IceBridge, and CryoSAT have gathered data on either the elevation of the snow surface or ice surface to estimate ice thicknesses, using isostatic equilibrium, over the Arctic ice pack. A major uncertainty for airborne or spaceborne lidar elevations conversions has been lack of knowledge regarding the snow dep...
Article
IceBridge airborne measurements are intended to fill the gap in data on the elevations of the ice sheets and the sea ice covers, caused by the interval between the demise of ICESat 1's laser altimetry in 2009 and the launch of ICESat2 approximately in 2016. IceBridge LiDAR elevation measurements from aircraft are intended to provide a means of obta...
Article
In this study, ICESat altimetry data are used to provide precise lake elevations of the Tibetan Plateau (TP) during the period of 2003–2009. Among the 261 lakes examined ICESat data are available on 111 lakes: 74 lakes with ICESat footprints for 4–7years and 37 lakes with footprints for 1–3years. This is the first time that precise lake elevation d...
Article
Although sea-ice extent in the Bellingshausen-Amundsen (BA) seas sector of the Antarctic has shown significant decline over several decades, there is not enough data to draw any conclusion on sea-ice thickness and its change for the BA sector, or for the entire Southern Ocean. This paper presents our results of snow and ice thickness distributions...
Article
Full-text available
Envisat Advanced Synthetic Aperture Radar (ASAR) Wide Swath Mode (WSM) images are used to derive C-band HH-polarization normalized radar cross sections (NRCS). These are compared with ice-core analysis and visual ship-based observations of snow and ice properties observed according to the Antarctic Sea Ice Processes and Climate (ASPeCt) protocol du...
Article
Antarctic Sea Ice Processes and Climate (ASPeCt) visual ship-based observations were conducted in the Bellingshausen Sea during the Sea Ice Mass Balance in the Antarctic (SIMBA) cruise in austral spring 2007. A total of 59 ASPeCt observations are compared to coincident satellite active and passive microwave data. Envisat and RADARSAT-1 C-Band HH-po...
Article
Little is known about errors in the atmospheric forcings of large-scale sea ice-ocean models around Antarctica. These forcings involve atmospheric reanalyses, typically those from the National Center for Environmental Prediction and National Center from Atmospheric Research (NCEP-NCAR), climatologies, and empirical parameterizations of atmosphere-i...
Article
Full-text available
Advanced Microwave Scanning Radiometer (AMSR-E) snow-depth data for Antarctic sea ice are compared with ship-based visual observations of snow depth, ice type and ridged-ice fraction, and with satellite C-band and Ku-band radar backscatter observations for two ship cruises into the Weddell Sea (ISPOL 2004–05, WWOS 2006) and one cruise into the Bell...
Article
Antarctic Sea Ice Processes and Climate (ASPeCt) ship-based ice observations, conducted during the Sea Ice Mass Balance in the Antarctic (SIMBA) and Sea Ice Physics and Ecosystem eXperiment (SIPEX) International Polar Year (IPY) cruises (September-October 2007), are used to validate remote-sensing measurements of ice extent and concentration. Obser...
Article
Full-text available
Three ice type regimes at Ice Station Belgica (ISB), during the 2007 International Polar Year SIMBA (Sea Ice Mass Balance in Antarctica) expedition, were characterized and assessed for elevation, snow depth, ice freeboard and thickness. Analyses of the probability distribution functions showed great potential for satellite-based altimetry for estim...
Article
Ice Station Belgica was commenced in late winter 2007 in the Bellingshausen Sea as part of Sea Ice Mass Balance in Antarctica (SIMBA), an IPY 2007 cruise on the research vessel N.B. Palmer. A primary objective was to build on the work of previous Antarctic drift station experiments to geophysically characterize sea ice in terms of thickness, surfac...
Article
The Sea Ice Mass Balance in the Antarctic (SIMBA) experiment was conducted from the RVIB N.B. Palmer in September and October 2007 in the Bellingshausen Sea in an area recently experiencing considerable changes in both climate and sea ice cover. Snow and ice properties were observed at 3 short-term stations and a 27-day drift station (Ice Station B...