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Abstract: Through analysis of over 2500 synthetic aperture radar (SAR) scenes spanning the period 1996–2008, we have compiled the most comprehensive dataset to date on landfast sea ice extent and its annual cycle in the Chukchi and Beaufort Seas. Our results show that landfast ice in the central and western Beaufort Sea forms earlier, breaks up later, occupies deeper water and extends further from shore than that in the Chukchi Sea. The differences in the timing of the annual landfast ice cycle are largely due to regional contrasts in the southward advance of pack ice in early winter and the onset of spring thaw. On the other hand, we suggest that the differences in landfast ice extent between the two seas are related to the number and distribution of recurring grounded ice features. These grounded features appear as “nodes” where the seaward landfast ice edge (SLIE) persistently recurs in multiple years. In the Beaufort Sea there are several such nodes that occur in water depths around 20m, giving rise to the similarity between the average SLIE location and the 20m isobath. We attribute the narrower landfast ice in the Chukchi Sea and lack of a consistent relationship with bathymetry to the sparsity of nodes in the Chukchi Sea. In comparing our results with data from the period 1973–76, we find that landfast ice extent in the Beaufort Sea has not changed significantly in the last four decades. However, in the Chukchi Sea our results show the landfast ice width has decreased by a coast-wide average of 13km over this period. We again attribute this difference between the two seas to the distribution of recurring grounded ice features. Over the 12 annual cycles in the study period, we identify trends indicating that landfast ice is forming later and disappearing earlier by approximately one week per decade. Although these trends are not statistically significant, they are in agreement with an overall shortening of the landfast ice season by as much as two months over the past three decades, revealed by a comparison with earlier findings for the period 1973–77. [Copyright &y& Elsevier]

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. [ABSTRACT FROM AUTHOR]

In this work, we evaluate landfast sea ice dynamics using ground-based radar interferometry. During two field campaigns in Utqiaġvik, Alaska, we collected three ∼24-h series of measurements on 16 May 2012 and 21–23 April 2021 using the Gamma portable radar interferometer (GPRI). These data enable examination of progressive strain of landfast ice on the sub-cm scale. The results indicate near spatially uniform divergence strains exceeding 10−6 in response to an increase in offshore winds from 0 to 7 m s−1. Exceptions to uniform divergence are grounded ridges with either negligible or reduced motion. We also track uniform vertical shifts in response to cm-scale sea level change correlated with NOAA model tidal predictions. We evaluate and take steps to remove contributions from moisture variability, thereby reducing potential errors from atmospheric effects to less than 5 mm. The results suggest that the GPRI can be a valuable tool for monitoring ice-covered coastal zones. The system has possible applications for monitoring tides and ocean surges and tracking small-scale deformation of otherwise stationary ice that can lead to fracture and destabilization. • We resolve wind-induced ice strain over kilometers with cm-scale accuracy. • We track vertical displacement of sea ice in microtidal environment. • We obtain minute-scale temporal resolution and sub-meter range resolution. • Allows accurate location and timing of episodic events e.g., cracks and detachments. • Atmospheric effects can be mitigated by removing phase change from static targets. [ABSTRACT FROM AUTHOR]

Landfast ice along the Arctic coasts plays an important role in supporting ecosystem services, local communities and offshore activities by industry. Seasonal predictions of landfast ice conditions are generally lacking in current seasonal forecasting products but are needed especially for planning of on-ice activities such as the construction of ice roads. This study focuses on the planned offshore development of Liberty Island where there is a need to generate seasonal forecasts for the construction of ice roads in Foggy Island Bay along the Beaufort Sea coast in northern Alaska. Due to the lack of prior in-situ observations of ice thickness in the region, a combination of newly obtained field measurements, remote sensing data analysis and modeling were employed to produce prototype seasonal forecasts of ice thickness in the landfast ice around Liberty Island. Seasonal forecasts initialized in September and March were built using Climate Forecast System seasonal forecast model data coupled with a single column ice model to forecast ice thickness that capture the start and end of the operational season, respectively. The results showed that the model forecasts had modest skill in capturing the timing of key ice thickness thresholds needed to support vehicle traffic during the start of the season in November–December but very limited skill with end of season and ice breakup forecasts. Much of the forecast skill was improved through bias correction but such improvement was hampered by the lack of long-term observational data in the region. Integration of the observational data and modeling is necessary to begin development of seasonal forecasts in this data sparse region. • Seasonal sea ice thickness forecasts developed for Foggy Island Bay, Alaska. • Forecasts needed to support ice road operations for Liberty Island development. • Required integration of field observations, forecast model data, and an ice model. • Forecast skill was improved through bias correction. [ABSTRACT FROM AUTHOR]