Arctic Sea Ice: Changing Operating Conditions in the Arctic Ocean

(from AMSA Report 2009)

Introduction

The Arctic sea ice cover is undergoing an extraordinary transformation that has significant implications for marine access and shipping throughout the Arctic basin. The Arctic Climate Impact Assessment, released by the Arctic Council at the Iceland Ministerial meeting in November 2004, documented that Arctic sea ice extent has been declining for the past five decades.

Research has also indicated that sea ice thickness has been decreasing during the same period, and the area of multi-year ice has also been declining in the central Arctic Ocean. Global Climate Models used in the ACIA and the Intergovernmental Panel on Climate Change Fourth Assessment Report (IPCC AR4 released in 2007) simulate a continuous decline in sea ice coverage through the 21st century. One ACIA model showed it is plausible that during midcentury, the entire Arctic Ocean could be ice-free for a short period in the summer, a finding that garnered significant media attention. Recent research (2006-2008) has indicated this plausible ice-free state of the Arctic sea ice cover may occur as early as 2040, if not sooner.

It is important to note that despite the remarkable, ongoing changes in Arctic sea ice and some uncertainty surrounding the output of the GCMs, no research and none of the GCM simulations have indicated that the winter sea ice cover of the Arctic Ocean will disappear during this century. This fact alone - that there will always be an Arctic sea ice cover to contend with - has important implications for all future Arctic marine activity and for the development of ship standards and measures to enhance Arctic marine safety and environmental protection.

The resulting sea ice conditions for future Arctic marine operations will be challenging and will require substantial monitoring and improved regional observations. This new Arctic Ocean of increasing marine access, potentially longer seasons of navigation and increasing ship traffic requires greater attention and stewardship by the Arctic states and all marine users. In assessments of ongoing and projected climate change, Arctic sea ice is a critical and highly visible element. Observed sea ice extents derived from satellite passive microwave data for 1979-2006 indicate a decrease or annual loss of 45,000 km2 of ice (3.7 percent decrease per decade). The same data analysis shows negative ice extent trends for each of the four seasons and each of the 12 months; the decline in summer extent (6.2 percent decrease per decade) is larger than in winter (2.6 percent decrease per decade).

Interestingly, the five smallest September ice-covered areas for the Arctic Ocean during the modern satellite record (1979-2008) have occurred in the five most recent seasons (2004-2008). Map 2.2 shows the sea ice coverage derived from satellite at the time of minimum extent of Arctic sea ice on September 16, 2007. This snapshot represents the minimum coverage of Arctic sea ice in the satellite era of observations. Striking are several notable features: the largely ice-free areas across the Russian Arctic coastal seas (north of the Eurasian coast), except for a small region in the western Laptev Sea; an ice edge that has retreated north of Svalbard and well north in the Beaufort and Chukchi seas; several ice-free passages through the Canadian Archipelago; and a large area of the central Arctic Ocean that previously has not been observed open or without even a thin ice cover.

These extraordinary changes in the summer ice cover of the Arctic Ocean, represented by a single, iconic satellite image for September 16, 2007, are major factors in the potential lengthening of the navigation season in regional Arctic seas, particularly in the summer. It should be noted though that during the same timeframe, the Fram Strait contained more ice than normal, underscoring the regional variability of sea ice extent.

Additional Sea Ice Trends and Research

Earlier observations from aircraft and ships, and three decades of daily satellite observations, suggest that the September 2007 minimum sea ice extent (Map 2.2) was the lowest since the early 1950s; however, the September 2008 minimum extent indicated a slightly larger area of sea ice coverage. The Arctic sea ice cover is at a maximum extent in March and this maximum coverage has also been observed to decrease at approximately 2 percent per decade during the period 1979-2008.

Map 2.2 Satellite images of summer sea ice cover 

These extent reductions have been observed in all seasons of a year, but perhaps more significant have been observations of a rapid decline of thick, multi-year sea ice in the central Arctic Ocean. A study of satellite data for winter during 1978-1998 revealed that the multi-year sea ice cover had declined by 7 percent per decade. A second trend analysis for 25 years of summer ice minima (1978 to 2003) reports a decline of multi-year sea ice as high as 9.2 percent per decade.

One important result of these trends should be a decrease in the presence of multi-year ice in the Arctic’s coastal seas where seasonal navigation and marine activity are highest. Arctic sea ice thicknesses have been much more difficult to monitor and evaluate during recent decades. Direct measurements of first year sea ice in the Arctic coastal seas by the Arctic and Antarctic Research Institute in St. Petersburg, the Russian Federation, along the Russian Arctic, generally yield 1-2 meter thicknesses. For the central Arctic Ocean, thicknesses of multi-year sea ice can be as high as 4-5 meters. One pioneering study using sea ice draft data acquired on submarine cruises (data from 1958-1976 compared with cruise data for 1993-1996) indicated a decrease in thickness at the end of the melt season for the central Arctic Ocean from 3.1 to 1.8 meters. This represented a volume decrease of 40 percent and a widespread decrease in sea ice draft. This 40 percent reduction was adjusted to 32 percent in a subsequent study once additional submarine tracks were added.

One key issue is that future sampling of Arctic sea ice thickness requires enhanced monitoring systems for more effective spatial and temporal measurements. Modern measurement systems such as electromagnetics, upward looking sonars and satellites have been developed that are improving thickness observations. Future Arctic navigation and all marine activity will depend on more frequent, reliable and near real-time sea ice thickness measurements.

Sea Ice Regional Trends: Canadian Maritime Arctic and Northwest Passage

The observed record of minimum sea ice extent for the eastern and western regions of the Canadian Arctic is illustrated in Graph 2.2. Although the observations for both regions show negative trends for the period 1969-2008, the year-to-year variability in coverage is quite extreme. Both regions also exhibit large differences for a given year; for example, in 1991 the western Canadian Arctic showed one of the highest or largest ice coverage areas, while in the eastern region a more normal coverage area at the summer minimum was observed. These regional variabilities create a challenge for seasonal operations. While these observations indicate an overall decrease in the ice cover of the waterways that comprise the Northwest Passage, the two key variabilities - year-to- year and spatial - create challenges for planners judging risk and the reliability of an Arctic marine transportation system for the long-term.

Graph 2.2 Sea ice variability in the Canadian Arctic and NWP 

The five models used in the ACIA revealed that the last regions of the Arctic Ocean with sea ice coverage in summer would be in the northern waterways of the Canadian Archipelago and along the northern coast of Greenland. The flow of more mobile multi-year ice through these waterways presents another potential challenge to marine operations. Enhanced satellite monitoring (with high resolution imagery) of this complex region will be a necessity if expanded marine operations beyond summer are to be realized.

Russian Maritime Arctic and Northern Sea Route

Map 2.2 indicates that a nearly ice-free summer passage could have been made in 2007 and 2008 from Kara Gate through to the Bering Strait along the length of the Northern Sea Route except for sea ice in the western Laptev Sea. Passive microwave satellite observations of sea ice in the Russian Arctic seas from 1979 to the present show large reductions in sea ice extent in summer and reductions in winter extent in the Barents Sea.

All of the ACIA model simulations and more recent IPCC AR4 model simulations confirm that large summer ice edge retreats should occur in the Laptev, East Siberian and western Chukchi seas. With a continued shrinkage of the fraction of multi-year sea ice in the central Arctic Ocean, it is plausible that fewer multi-year ice floes may be observed along the navigable eastern passages of the Northern Sea Route. Long-term fast ice thickness measurements of the four Russian marginal seas (Kara, Laptev, East Siberian and Chukchi seas) have been analyzed for trends using 65-year observational records (1930s to 1990s). Long-term trends are small and inconclusive: the trends are small (approximately 1 centimeter per decade); the trends for the Kara and Chukchi seas are positive and the trends for the Laptev and East Siberian seas negative. A review of recent assessments, observations and studies indicate that there remains much to understand about the present and future trends in Arctic sea ice.

The operating conditions for Arctic ships will remain challenging, particularly in winter. It is also highly plausible that Arctic sea ice will be more mobile, particularly in spring, summer and autumn, as the cover continues to retreat from Arctic coastlines. Arctic coastal seas may experience increased ridging of seasonal sea ice, potentially creating more difficult operating conditions for marine navigation. The observed records of sea ice extent in the Canadian and Russian Arctic areas display high inter-annual variabilities. Such year-to year variability poses a serious challenge to risk and the overall reliability of Arctic marine transport systems. Three key conclusions with direct relevance to Arctic shipping include:

• Arctic sea ice has been observed to be diminishing in extent and thinning for five decades. Also, model simulations indicate a continuing retreat of Arctic sea ice throughout the 21st century. However, no research indicates Arctic sea ice will disappear completely and a substantial winter sea ice cover will remain.

• Even a brief ice-free period in summer for the Arctic Ocean would mean the disappearance of multi-year sea ice in the central Arctic Ocean. Such an occurrence would have significant implications for design, construction and operational standards of all future Arctic marine activities.

• Observed sea ice trends and GCM simulations show coastal Arctic regions to be increasingly ice-free, or nearly ice-free, for longer summer and autumn seasons. Longer open water seasons increase the potential for greater coastal erosion, which can impact support infrastructure for Arctic development and marine transportation.

Regarding future needs, a key requirement is the development of high resolution, regional sea ice models that can provide more robust and realistic forecasting of marine operating conditions. There is also a critical requirement for more real-time sea ice observations, especially ice thickness measurements, to support all future Arctic marine uses. The national ice centers and ice services are critical providers of such sea ice information and greater international collaboration among the centers will enhance the development of more integrated products. New satellite sensors hold the promise of providing greater, near real-time ice thickness information for Arctic ships that are underway on future voyages.

Arctic Council, 2009, Arctic Marine Shipping Assessment Report, Arctic Council.©