In this work, we evaluate landfast sea ice dynamics using ground-based radar interferometry. During two field campaigns in Utqiagvik, Alaska, we collected three similar to 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 investigate the application of ground-based radar interferometry for measuring flexural–gravity waves in sea ice. We deployed a GAMMA Portable Radar Interferometer (GPRI) on top of a grounded iceberg surrounded by landfast sea ice near Utqiaġvik, Alaska. The GPRI collected 238 acquisitions in stare mode during a period of moderate lateral ice motion during 23–24 April 2021. Individual 30 s interferograms exhibit ∼ 20–50 s periodic motion indicative of propagating infragravity waves with ∼ 1 mm amplitudes. Results include examples of onshore wave propagation at the speed predicted by the water depth and a possible edge wave along an ice discontinuity. Findings are supported through comparison with on-ice Ice Wave Rider (IWR) accelerometers and modeled wave propagation. These results suggest that the GPRI can be a valuable tool to track wave propagation through sea ice and possibly detect changes in such properties across variable ice conditions.

Abstract. We investigate the application of ground-based radar interferometry for measuring flexural-gravity waves in sea ice. We deployed a Gamma Portable Radar Interferometer (GPRI) on top of a grounded iceberg surrounded by landfast sea ice near Utqiaġvik, Alaska. The GPRI collected 238 acquisitions in stare-mode during a period of moderate lateral ice motion during 23–24 Apr 2021. Individual 30-second interferograms exhibit ~20–50 s periodic motion indicative of propagating infragravity waves with ~1 mm amplitudes. Results include examples of onshore wave propagation at the speed predicted by the water depth and a possible edge wave along an ice discontinuity. Findings are supported through comparison with on-ice Ice Wave Rider (IWR) accelerometers and modeled wave propagation. These results suggest that the GPRI can be a valuable tool to track wave propagation through sea ice and possibly detect changes in such properties across variable ice conditions.

Nearly 90 Lagrangian surface drifters were deployed and often recovered and re-deployed in lower Cook Inlet and Kachemak Bay from 2003 through 2007 and from 2012 through 2017. Velocity vectors calculated from the hourly position data by central finite-differences were low-passed filtered to create maps of the mean, sub-tidal surface circulation. The circulation maps, while generally consistent with the results of Burbank (1977) and Muench et al. (1978), provide new detail showing anti-cyclonic circulation around Kalgin Island, a single cyclonic circulation cell in outer Kachemak Bay, and two circulation cells, one cyclonic and the other anti-cyclonic, in inner Kachemak Bay. (c) 2021 The Author. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

In light of recent Arctic change, there is a need to better understand sea ice dynamic processes at the floe scale to evaluate sea ice stability, deformation, and fracturing. This work investigates the use of the Gamma portable radar interferometer (GPRI) to characterize sea ice displacement and surface topography. We find that the GPRI is best suited to derive lateral surface deformation due to mm-scale horizontal accuracy. We model interferometric phase signatures from sea ice displacement and evaluate possible errors related to noise and antenna motion. We compare the analysis with observations acquired during a drifting ice camp in the Beaufort Sea. We used repeat-scan and stare-mode interferometry to identify two-dimensional shear and to track continuous uni-directional convergence. This paper demonstrates the capacity of the GPRI to derive surface strain on the order of 10−7 and identify different dynamic regions based on sub-mm changes in displacement. The GPRI is thus a promising tool for sea ice applications due to its high accuracy that can potentially resolve pre- and post-fracture deformation relevant to sea ice stability and modeling.

We developed and deployed two inertial measurement units on mobile pack ice during a U.S. Navy drifting ice campaign in the Beaufort Sea. The ice camp was more than 1000 km from the nearest open water. The sensors were stationed on thick (>1 m) first- and multi–year ice to record 3-D accelerations at 10 Hz for one week during March 2020. During this time, gale-force winds exceeded 21 m per second for several hours during two separate wind events and reached a maximum of 25 m per second. Our observations show similar sets of wave bands were excited during both wind events. One band was centered on a period of ~14 s. Another band arrived several hours later and was centered on ~3.5-s. We find that the observed wave bands match a model dispersion curve for flexural gravity waves in ~1.2-m ice with a Young’s modulus of 3.5 GPa under compressive stresses of ~0.3 MPa. We further evaluate the bending stress and load cycles of the individual wave bands and their potential role in break-up of sea ice. This work demonstrates how observations of waves in sea ice using these and similar sensors can potentially be a valuable field-based tool for evaluating ice mechanics. In particular, this approach can be used to observe and describe the combined mechanical behavior of consolidated floes relevant for understanding sea ice mechanical processes and model development.

Abstract Using short‐temporal baseline interferometric synthetic aperture radar, we capture instantaneous images of a persistent field of infragravity waves propagating through sea ice near Barrow, Alaska, during January 2015. We estimate wave amplitudes to be between 1.2 and 1.8 mm. Curvature of wavefronts is consistent with refraction of waves entering shallow water from a source region north of Barrow. A shallow water wave model indicates that the geometry of the wavefronts is relatively insensitive to the source location, but other evidence suggests the waves may have originated in the North Atlantic, making this perhaps the longest observed propagation path for waves through ice. We also note that steepening of the waves entering shallow water can increase the peak strain by an order of magnitude, suggesting that infragravity waves may play a role in determining the location of the landfast ice edge with respect to water depth.

Oceanographic observations made during the Sound Predictions 2009 field experiment in Prince William Sound, Alaska, have documented rapid changes in the upper water column (0–40m) circulation. An assortment of drifting buoys, sampling four different depths, and HF radar surface current mapping, revealed three modes of circulation: anticyclonic, open cyclonic, and closed cyclonic. Each mode was observed at least once within an 18-day window, and the transition between them took as little as a day. Time-resolved hydrographic measurements show that the mass field was variable, but generally arranged such that the surface geostrophic flow should be in a closed-core cyclonic eddy configuration. Observations show that the mass field was likely influenced by relatively low salinity water flowing into Prince William Sound from the shelf, and from local freshwater input. We quantitatively examine why a closed-core circulation was not always observed by focusing on the transition between the closed and open cyclonic flow patterns. The western region of the central sound is a key area for this transition. Here, the high-frequency radar revealed that the closed circulation was established when the net flow shifted direction from northward to southward. A detailed comparison of the meridional geostrophic and wind-driven flows, using measured winds and hydrographic data from CTD profiles and two autonomous vehicles, shows that the geostrophic flow was mostly southward while the wind-driven flow was mostly northward. A net southward flow can be caused by a decrease in the northward wind-driven flow or an increase in the southward geostrophic flow.

Using monthly mean sea ice velocity data obtained from the International Arctic Buoy Programme (IABP) for the period of 1979–1998 and the monthly mean NCEP/NCAR re-analysis dataset (1960–2002), we investigated the spatiotemporal evolution of the leading sea ice motion mode (based on a complex correlation matrix constructed of normalized sea ice motion velocity) and their association with sea level pressure (SLP) and the predominant modes of surface wind field variability. The results indicate that the leading winter sea ice motion mode’s spatial evolution is characterized by two alternating and distinct sea ice modes, or their linear combination. One mode (M1) shows a nearly closed cyclonic or anti-cyclonic circulation anomaly in the Arctic Basin and its marginal seas, resembling to a large extent the response of sea ice motion to the Arctic Oscillation (AO), as many previous studies have revealed. The other mode (M2) displays a coherent cyclonic or anti-cyclonic circulation anomaly with its center close to the Laptev Sea, which has not been identified in previous observational studies. In fact, M1 and M2 respectively reflect the responses of sea ice motion to two predominant modes of winter surface wind variability north of 70°N, which well correspond, with slight differences, to the first two modes of EOF analysis of winter monthly mean SLP north of 70°N. These slight differences in SLP anomalies lead to a difference of M2 from the response of sea ice motion to the dipole anomaly. Although the AO significantly influences sea ice motion, it is not crucial for the existence of M1. The new sea ice motion mode (M2) has the largest variance and clearly differs from the response of winter monthly mean sea ice motion to the dipole anomaly in SLP fields, and corresponding SLP anomalies also show differences compared to the dipole anomaly. This study indicates that in the Arctic Basin and its marginal seas, slight differences in SLP anomaly patterns can force distinctly different sea ice motion anomalies.

The morphology, stability and duration of seasonal landfast sea ice in Alaska's coastal zone is changing alongside large-scale ice thinning and retreat. The extent and complexity of change at the local level requires an integrated observing approach to assess implications of such change for coastal ecosystems and communities that rely on or make use of the sea-ice cover. Barrow, Alaska is an example of a community that experiences and utilizes a broad range of sea-ice types and conditions. The local population is increasingly forced to adapt to less stable sea ice, loss of multiyear ice and a shorter ice season. We are working toward an integrated coastal ice observatory to monitor landfast and adjacent pack ice and to maximize the usefulness of information to the community. The observatory includes: (1) satellite remote-sensing datasets distributed in near real-time; (2) a coastal sea-ice radar and webcam that monitor ice movement and evolution; (3) a mass-balance site that provides temperature profiles and thickness information for ice and snow; (4) sea-level measurements; (5) periodic ice thickness surveys using direct drilling and electromagnetic induction sounding; and (6) a program of regular, undirected observations by Iñupiat sea-ice experts. We examine two significant landfast ice breakout events off Barrow in spring of 2007. During these events, Barrow's subsistence whaling community partook in a successful hunting season observing and responding to these breakout events and their impacts on ice stability. Using local expert knowledge to parse geophysical datasets obtained from the observatory has provided deeper insight into different approaches for assessing ice stability, and integrating information on ice growth, origin, morphology, and dynamics, as well as winds, weather, and currents.

This paper reveals a new mode of winter (October–March) monthly mean atmospheric intraseasonal variability characterized by a seesaw structure in sea level pressure (SLP) anomalies between the Barents Sea and the Beaufort Sea with an equivalent barotropic structure. The Beaufort High varies out of phase with the Siberian High. Compared to the Arctic Oscillation (AO) and the dipole anomaly, the effect of this mode on Fram Strait sea ice flux is the most important so far, although it accounts for only 9.1% of the variance. The Beaufort High itself is not crucial for sea ice flux through Fram Strait.

A two-dimensional barotropic, coupled, ocean–ice model with a space resolution of 55.5 km and driven by atmospheric forces, river run-off, and sea-level slope between the Pacific and the Arctic Oceans, has been used to simulate the vertically averaged currents and ice drift in the Arctic Ocean. Results from 43 years of numerical simulations of water and ice motions demonstrate that two wind-driven circulation regimes are possible in the Arctic, a cyclonic and an anti-cyclonic circulation. These two regimes appear to alternate at 5–7 year intervals with the 10–15 year period. It is important to pollution studies to understand which circulation regime prevails at any time. It is anticipated that 1995 is a year with a cyclonic regime, and during this cyclonic phase and possibly during past cyclonic regimes as well, pollutants may reach the Alaskan shelf. The regime shifts demonstrated in this paper are fundamentally important to understanding the Arctic's general circulation and particularly important for estimating pollution transport.

: Paleoclimate inferred from the Vostok ice core provides tantalizing evidence that increases in atmospheric CO2 are dynamically linked with increases in atmospheric temperature (Jouzel et al., 1987; Barnola et al., 1987; Genthon et al., 1987). However, the mechanisms responsible for the temporal and spatial scales of the accompanying temperature change are not understood because, in part, the ocean's role is not well understood. New technology is required to see inside the global oceans where vasts amount of heat are redistributed and eventually exchanged with the atmosphere. Waves and other features at large scales, approximately 100 to 10,000 km, having time scales less than centuries are virtually unexplored but these scales are important for understanding climate change (Gill, 1982; Philander, 1990). We are developing novel acoustic instruments that have the potential for measuring these scales in the global oceans in real-time. The cost for these measurements is projected to be less than the costs of mapping temperature and other variables in the atmosphere (Spiesberger, 1992). (MM)

Kelvin waves excited by the wind in the western equatorial Pacific Ocean propagate eastward to the boundary and then poleward along the coast. Poleward propagating coastal Kelvin waves produce a signal that propagates away from the coast as westward propagating Rossby waves with amplitude proportional to the amplitude of the passing Kelvin wave. The frequency of the Kelvin wave signal sets the frequency of the Rossby response and the possible wavelengths through the Rossby dispersion relation. This paper examines the role of coastal Kelvin waves in the mid-latitude response of the ocean in general, and the mid-latitude 1982-1983 El Nino response in particular, using two primitive equation numerical models of the equatorial and northeast Pacific Oceans. The equatorial model, in agreement with observations, shows a large amplitude Kelvin wave propagating eastward along the equator as a prelude to the 1982-1983 El Nino and then poleward along the coast. A time series of the model coastal signal from 1975 through 1984, extracted from the equatorial model, forces a northeast Pacific Ocean model near the coast at 18 degrees N, allowing signals to propagate from the equator through low-latitudes to mid-latitudes. Model results show, (1) that the coastal Kelvin wave initializes and defines the frequency of the offshore propagating Rossby wave (2) that the Kelvin Rossby response is fundamental to the development of the mid-latitude 1982-1983 El Nino and, (3) that Rossby waves at 30 degrees N extend the signal seaward from the coast several thousand kilometers, although the Rossby wave signal loses its identity in the region of the California Current several hundred kilometers from the coast.