Mark Johnson

The primary goal of this paper is to demonstrate the dependence of Arctic Ocean sea-ice transport pathways on climate variations. We build our analysis on the results of Proshutinsky and Johnson (1997), Johnson and others (1999), Polyakov and others (1999) and Proshutinsky and others (1999), where we have shown that wind-driven ice motion and upper ocean circulation alternate between anticyclonic and cyclonic states. Shifts between regimes occur at 5−7 year intervals, resulting in a 10−15 year period. The anticyclonic circulation regime has been observed in our model results for 1946−52,1958−62,1972−79,1984−88 and 1998−present. The cyclonic circulation regime prevailed during 1953−57,1963−71,1980−83 and 1989−97. The regime shifts are fundamentally important to understanding the Arctic’s general circulation and particularly useful for estimating pollution transport by sea ice and surface waters. It is important to pollution studies to understand which circulation regime prevails. Ini...

Variability in sea ice conditions, combined with strong couplings to the atmosphere and the ocean, lead to a broad range of complex sea ice dynamics. More in-situ measurements are needed to better identify the phenomena and mechanisms that govern sea ice growth, drift, and breakup. To this end, we have gathered a dataset of in-situ observations of sea ice drift and waves in ice. A total of 15 deployments were performed over a period of 5 years in both the Arctic and Antarctic, involving 72 instruments. These provide both GPS drift tracks, and measurements of waves in ice. The data can, in turn, be used for tuning sea ice drift models, investigating waves damping by sea ice, and helping calibrate other sea ice measurement techniques, such as satellite based observations.

Travel times of acoustic signals were measured between the bottom-mounted Kaneohe source near Oahu and seven SOSUS stations at 3000–4000-km distance during 1983–1989. The Naval Research Laboratory hydrodynamic eddy resolving model yields changes in travel time whose standard deviations are consistent with the data. The model predicts that between 1981–1993, Rossby waves modify travel times by one second. Mesoscale eddies modify travel times little compared to Rossby waves. The largest Rossby waves are descendants of El Nino. Travel times changes are sensitive indicators of predictable features in the Naval Research Laboratory model. [Work supported by the Strategic Environmental Research and Development Program, managed by the Advanced Research Projects Agency.]

The difficulties in detecting anthropogenic changes in ocean temperature due to the industrial revolution are discussed using acoustic thermometry data taken between Oahu and seven SOSUS receivers at distances of 3000–4000 km. Measurements were made in late 1983, and over two 5-month intervals between 1987 and 1989. The travel times are dominated by interannual fluctuations. Two hydrodynamic ocean models are used to identify plausible oceanic features that could cause these variations. Modeled El Niños and La Niñas exhibit oceanic teleconnections between the Equator and mid-latitudes that lead to Rossby waves that propagate westward at mid−latitudes. Rossby waves are the dominant model features which affect the modeled acoustic travel times, and hence section-averaged temperatures in the eastern North Pacific. Modeled predictions of the travel times are significantly different than some of the data. The magnitude and rates of changes of the data are the same as those which result fr...

Two numerical models utilizing primitive equations (two momentum equations and a mass continuity equation) simulate the oceanography of the Pacific Ocean from 20°S to 50°N. Results show Kelvin waves thousands of kilometers long propagating from the equator to the northeast Pacific Ocean. Kelvin waves are very long waves that propagate along the equator and along solid boundaries with the boundary to their right. They are important to simulations of ocean circulation along the North American coast because they carry information at seasonal and longer periods from the equator poleward. Modeling an extensive region such as the Pacific Ocean with adequate two-dimensional resolution places heavy demands on computer memory and storage. We have found that the best way to examine the abundant model data is through visualization, by animating the appro priate model fields and viewing the time history of each model simulation as a color movie. The animations are used as research products to a...

There is a wide consensus within the polar science, meteorology, and oceanography communities that more in situ observations of the ocean, atmosphere, and sea ice are required to further improve operational forecasting model skills. Traditionally, the volume of such measurements has been limited by the high cost of commercially available instruments. An increasingly attractive solution to this cost issue is to use instruments produced in-house from open-source hardware, firmware, and postprocessing building blocks. In the present work, we release the next iteration of the open-source drifter and wave-monitoring instrument of Rabault et al. (see “An open source, versatile, affordable waves in ice instrument for scientific measurements in the Polar Regions”, Cold Regions Science and Technology, 2020), which follows these solution aspects. The new design is significantly less expensive (typically by a factor of 5 compared with our previous, already cost-effective instrument), much easi...

1. The recognized importance of the annual cycle of sea ice in the Arctic to heat budgets, human behavior, and ecosystem functions, requires consistent definitions of such key events in the ice cycle as break-up and freeze-up. An internally consistent and reproducible approach to characterize the timing of these events in the annual sea-ice cycle is described. An algorithm was developed to calculate the start and end dates of freeze-up and break-up and applied to time series of satellite-derived sea-ice concentration from 1979 to 2013. Our approach builds from discussions with sea-ice experts having experience observing and working on the sea ice in the Bering, Chukchi and Beaufort Seas. Applying the algorithm to the 1979–2013 satellite data reveals that freeze-up is delayed by two weeks per decade for the Chukchi coast and one week per decade for the Beaufort coast. For both regions, break-up start is arriving earlier by 5–7 days per decade and break-up end is arriving earlier by 1...

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-u...

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 prom...

A simple model of the Arctic Ocean and Greenland Sea, coupled to a thermodynamic sea ice model and an atmospheric model, has been used to study decadal variability of the Arctic ice-ocean-atmosphere climate system. The motivating hypothesis is that the behavior of the modeled and ultimately the real climate system is auto-oscillatory with a quasi-decadal periodicity. This system oscillates between

Examination of records of fast ice thickness (1936–2000) and ice extent (1900–2000) in the Kara, Laptev, East Siberian, and Chukchi Seas provide evidence that long-term ice thickness and extent trends are small and generally not statistically ...

1. Abstract The recognized importance of the annual cycle of sea ice in the Arctic to heat budgets, human behavior, and ecosystem functions, requires consistent definitions of such key events in the ice cycle as break-up and freeze-up. An internally consistent and reproducible approach to characterize the timing of these events in the annual sea-ice cycle is described. An algorithm was developed to calculate the start and end dates of freeze-up and break-up and applied to time series of satellite-derived sea-ice concentration from 1979 to 2013. Our approach builds from discussions with sea-ice experts having experience observing and working on the sea ice in the Bering, Chukchi and Beaufort Seas. Applying the algorithm to the 1979–2013 satellite data reveals that freeze-up is delayed by two weeks per decade for the Chukchi coast and one week per decade for the Beaufort coast. For both regions, break-up start is arriving earlier by 5–7 days per decade and break-up end is arriving earlier by 10–12 days per decade. In the Chukchi Sea, " early " break-up is arriving earlier by one month over the 34-year period and alternates with a " late " break-up. The calculated freeze-up and break-up dates provide information helpful to understanding the dynamics of the annual sea-ice cycle and identifying the drivers that modify this cycle. The algorithm presented here, and potential refinements, can help guide future work on changes in the seasonal cycle of sea ice. The sea-ice phenology of freeze-up and break-up that results from our approach is consistent with observations of sea-ice use. It may be applied to advancing our understanding and prediction of the timing of seasonal navigation, availability of ice as a biological habitat, and assessment of numerical models.

To help validate the model and understand better the Cook Inlet tidal rips, 50 drifting buoys were deployed for us by Cook Inlet Spill Prevention and Response, Inc. (CISPRI). Velocities are computed using centered differences. Tidal fronts are typically associated with convergence zones. In Cook Inlet, drifting sea ice tends to collect along tide rip fronts thereby providing strong visual signatures for frontal locations.

A 3-D tidal model (Finite Volume Community Model – FVCOM) of Cook Inlet with spatial resolution of 160 m near the coastline and 13 km along the open boundary has been used to simulate the eight major tidal waves in this region (five semidiurnal and three diurnal). Tidal data are from satellite-based archives of tidal constituents for the Gulf of Alaska and Northern Pacific Ocean. Model results of the tidal elevations and phases of the four major waves are in good agreement with observations. Radar backscatter (brightness) from sea ice is typically larger than from open water. As a consequence, the ice edge (frontal) location exhibits a relatively large spatial gradient in radar backscatter. Frontal locations identified from nine SAR images acquired in February 2002, December 2003, January 2004, and February 2004 show that the greatest number of frontal features occurs in a zone extending southwestward from near the West Foreland to along and beyond the eastern shore of Kalgin Island. This zone roughly corresponds to the location of the West Rip and qualitatively agrees with the buoy observations and model results.

A simple statistical analysis was conducted to estimate the averaged absolute difference and standard deviation between model-predicted and observed Lagrangian velocities for drifters #36190 and #36193 experiments, and results are summarized in Table 2.1. The averaged model-data absolute difference for 4 deployments of drifter #36190 was 30 cm/s for U (east-west component) and 42 cm/s for V (north-south component) for the case with the only tidal force.

This difference increased by about 2-3 cm/s when the T/S, winds, and surface heat flux were included. The standard deviation value was about 10 cm/s larger than the absolute difference values. The similar results were also shown for drifter #36193. This error is much smaller than the maximum value of tidal current velocity in the inlet but was the same order
of magnitude as wind- and buoyancy-driven subtidal currents, suggesting that it is critical to resolve accurately the subtidal currents in Cook Inlet in order to provide the realistic water transport process in this region.

The results clearly show that the RAMS failed to predict the relatively large wind event even for a short time period of 24 hours. In addition to the wind speed, the model also seemed to have troubles in capturing the right direction during air-frontal passages. For example, in late September, the wind measurement shows a strong southward wind velocity of ~15 m/s at both NSFA2 and AUGA2, but RAMS predicted that the maximum wind velocity was directed eastward. The same evidence occurred in late October and November. In November, the phase of the model- predicted wind seemed to have a shift from the observed wind.

This comparison suggests that the Alaska regional RAMS needs to be improved in order to make it useful to drive the ocean model. A better meso-scale meteorological model system with data assimilation should be developed to provide a reliable and accurate wind field in Cook Inlet for the hindcast application and also ocean model simulation. Our Lagrangian particle tracking experiment clearly shows that the buoyancy- and wind-driven circulations play a critical role for particle trajectories and water transports in Cook Inlet. Without improvement in the meteorological forcing fields, it is impossible to simulate accurately the trajectories of drifters deployed in this region.