Sea Ice Outlook | 2009 Outlook

• Pan-Arctic
• Regional

Overview

For the 2009 SEARCH Sea Ice Outlook, regional perspectives on ice evolution during the summer had been solicited, both to synthesize relevant field observations and modeling activities and to encourage communication between different sea ice experts and user groups. Nine different individuals or groups responded to this request, with input ranging from coupled ice-ocean model ensemble simulations and statistical/semi-empirical models to heuristic models and tracking of sea ice at the regional level using remote sensing.

Anticipating ice development at the regional scale is in some ways more challenging than at the pan-arctic level because the difficulties and uncertainties characterizing pan-arctic forecasts are amplified because of the even greater role local weather patterns and other small scale anomalies can play. At the same time, anomalies in local ice conditions, such as the presence of mult-year ice discussed for the North West Passage (NWP below), may persist well into the melt season and provide some measure predictability. Local knowledge of recurring ice retreat patterns constrained by, e.g., topography or ocean currents can further enhance outlooks at the regional scale, which is also discussed for the NWP below.

Contributors were asked to provide, where possible, a categorical forecast of ice conditions over the summer, i.e., light, medium (normal) or heavy ice conditions. A summary of these contributions by region indicates that responses ranged from quantitative assessments of specific variables (opening dates provided by Maslanik et al., ensemble simulations by Zhang, 2-week break-up forecast for Barrow by Petrich and Eicken) to broader assessments integrating a range of data sources (state of NWP and Northern Sea Route).

Northwest Passage:
Open – Zhang;
Closed – Howell and Duguay (Parry Strait Route);
Closed – Arbetter et al. (Parry Strait Route)

Nares Strait:
Open with inflow of ice from High Arctic – Gudmandsen

Northern Sea Route:
Most likely open but less drastic ice retreat than in 2007 – Pokrovsky;
Open – Maslanik et al.

Chukchi and Beaufort Seas:
Early onset of melt and opening (Maslanik et al.);
In Barrow region lighter than normal ice conditions with sluggish initial ice retreat – Eicken et al.;
Potential masking of old ice as a result of complicated ice decay processes – Barber et al.

High Arctic:
Lighter ice conditions than normal – Maslanik et al.;
Sluggish melt (observation from buoys, not forecast) – Perovich

Greenland and Barents Seas:
Below normal ice conditions (observations from remote sensing, not forecast) – Gerland and Hall

The diversity of categories and the selective focus on aspects of ice conditions that are inherently more predictable (e.g., impact of multi-year ice on summer ice conditions) preclude any rigorous evaluation of the predictive success of the regional outlook. However, a majority of the contributions were reasonably accurate with respect to the anticipated ice conditions. In general, it appears that statistical, semi-empirical as well as heuristic approaches fare reasonably well because they are able to build on sparse or qualitative information concerning the initial conditions in a specific sub-region. Ice-ocean model simulations, on the other hand, have requirements with respect to data density and quality, e.g., for observed ice thickness fields used in initialization of model runs, that are currently not being met by existing data sources (with the exception of, e.g., satellite-observed ice concentration fields). Exploring ways of melding different forecasting approaches may hold some promise in the future.

The evolution of regional ice conditions is discussed further below and in more detail by the individual contributors. In summary, all sub-regions of the Arctic appear to have been characterized by sluggish ice melt and retreat, due in part to above average cloudiness and atmospheric circulation favoring cooler conditions (see pan-arctic outlook summary discussion). In the Siberian Arctic and the Chukchi Sea, the absence of multi-year ice still resulted in lighter than normal ice conditions, as anticipated by outlook contributors. In the Beaufort Sea and the high Canadian Arctic, multi-year ice persisted throughout summer, resulting in medium to slightly lighter than normal ice conditions. In the NWP region, multi-year ice distribution patterns suggest that the coming year will only see limited openings in the northern parts of the route.

Feedback from local observers and vessels operating in the North American Arctic also highlights the need for further work on reconciliation between different ice nomenclatures and ice information derived from different sources (satellite remote-sensing, ship-based observations, buoys etc.). Thus, as commented on by one of the mariners taking a sailboat through the NWP, at the regional scale ice located outside the proper ice edge (which may be defined by the 10 or 15% ice concentration contour) may still present a formidable obstacle to progress with a small vessel. Similarly, data transmitted from an ice mass balance buoy located well outside of the ice edge in the western Chukchi Sea, suggest that while not of climatological importance, pans and cakes of ice may still be relevant as potential ice habitat or navigational hazard.

Regional perspectives (full details provided in individual submissions)

Tracking of ice conditions through the Northwest Passage (NWP) highlighted the importance of having a clear definition of what constitutes an “open” passage. Ensemble model simulations by Zhang suggested an opening of the passage along several routes. As detailed in his contribution, initial underprediction of ice conditions improved as the season evolved and the window of higher predictive skill extended out to include the September minimum ice extent period. A key challenge with coupled ice-ocean model runs appears to be the limited spatial resolution in regions with complicated topography. At the same time, local observers reported significant remnants of ice that presented potential hazards to non-ice strengthened vessels.

As highlighted by Arbetter et al. in their contribution, in particular from the perspective of navigation in ice-covered waters, it is important to recognize differences between different forecasting and remote-sensing approaches as to the definition of ice extent, location of the ice edge and related variables describing ice conditions. Here, considerable value can be derived from ship-based observations, aerial overflights, and drifting (mass-balance) buoys that provide a more accurate picture of the distribution of different ice types.

Howell and Duguay’s approach of deducing likely summer evolution of the Parry Channel route of the NWP based on past conditions of multi-year ice distributions was quite successful in predicting ice evolution at high spatial resolution. Figure 1 illustrates an example of extreme years in this region in relation to the past three years.

Gudmandsen and Kwok point out that the Lincoln Sea appears now to be recovering from the great ice outflow events of 2007 and 2008, with thicker ice building up after reestablishment of an ice barrier to the South.

The distribution of multi-year ice also impacted ice retreat in the Beaufort Sea, where sluggish melt damped by high cloudiness helped preserve large swaths of ice in the eastern Beaufort Sea. This ice will likely affect both winter and spring ice conditions in the coming year. In contrast, lack of multi-year ice in the Chukchi Sea at the start of the melt season had allowed significant retreat of sea ice. Impacts of this retreat include walrus congegrating in large numbers along the eastern Chukchi coast, similar to but not quite as extensive as in 2007. Predictions of melt onset by Maslanik et al. were on target for the Chukchi Sea, but did not anticipate the evolution of cloudiness in June and July that greatly slowed melt. The impact of low shortwave fluxes came out well in two-week forecasts of a semi-empirical break-up model forced with output from a long-range weather forecast (contribution by Petrich and Eicken). Break-up in 2009 at Barrow occurred later than during any of the previous nine years (Figure 2).

Barber and colleagues report about the masking of different signatures of old ice (first-year ice and multiyear ice that survived summer melt) in the Beaufort Sea with potential implications for assessing the extent and state of the ice cover. They found that invasion of seawater into rotten ice and decay of first-year ice resulted in a complex mixture of ice types not distinguished properly in remote sensing data.

In the Siberian Arctic, heuristic forecasts by Pokrovsky and statistical forecasts by Maslanik et al. predicted opening of the Northern Sea Route, which were on target (Figure 3). However, as with the NWP, opening based on the position of the 15% or 10% ice concentration contour apparent from passive microwave satellite imagery may not necessarily capture ice conditions in some of the straits that can substantially hamper maritime traffic. Pokrovsky points to the importance of warm Atlantic water inflow in maintaining the below-normal ice conditions in the Barents and Kara Seas, and highlights the need for reliable forecasts of sea surface temperature fields in the North Atlantic necessary to improve the Outlook.

Figure 1: Spatial distribution of multi-year ice (in tenths) within the Western Parry Channel region of the Northwest Passage on May 1st for a heavy ice year (2004), a light year ice (1999) and the last three years. Data is from the Canadian Ice Service. (for details, see contribution by Howell and Duguay).

Figure 2: Break-up timing and solar shortwave energy incident at the surface (mean and cumulative shown on bottom and left axis, respectively) for 2009 (thick red line) and other recent years. Curves terminate at observed break-up. The shortwave flux is used as an indicator for radiative forcings. The grey area at the top corresponds to the seasonal stage at which ice break-up is imminent and determined by local sealevel and winds. Details at www.gi.alaska.edu/snowice/sea-lake-ice/Brw09/forecast/. (for details see contribution by Eicken et al.)

Figure 3: Ice distribution along the Northern Sea Route based on QuikScat radar data provided by Son Nghiem (JPL) for September 29, 2009. Note that while the passage appears to be open, the National Ice Center (NIC) indicates conditions were only marginally “open” from a maritime traffic perspective (see NIC contribution).

Individual 2009 Regional Summary Report Contributions:

Download All Individual 2009 Regional Summary Report Contributions (1.7MB - PDF)

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Individual Submissions:
Barber et al. Eicken et al. Gudmandsen	Gudmandsen and Kwok Howell and Duguay Pokrovsky Zhang