Sea Ice and Rising Ocean Temperature Facts and Discussion

New Opportunities for Shipping, Oil and Gas Exploration, and Tourism

As sea ice extent decreases, the Arctic becomes more accessible to marine traffic, including shipping, oil and gas exploration, and tourism. Shipping traffic through the Arctic has steadily increased in recent years due to reduced sea ice. Declining sea ice opens up shipping lanes that were previously inaccessible and lengthens the navigation season. Essentially ice-free summers, predicted to occur by the middle of this century, would greatly increase the opportunity for shipping through the arctic region and create more opportunities for offshore oil and gas exploration and tourism.

These changes represent an increase in economic opportunities and are attracting a broad range of new interest in the Arctic. However, they also bring many risks and challenges. Risks include oil spills and other environmental disasters, introduction of invasive species, marine mammal ship strikes, disruption of migratory patterns of marine mammals, and increased anthropogenic (human-caused) noise. In addition, there is currently a lack of infrastructure in the Arctic to support these activities. Constructing the needed infrastructure, such as ports, buildings, and oil spill emergency response equipment, will be expensive and time-consuming. Also, the weather and ocean conditions in the Arctic can be extreme and unpredictable, and can change rapidly, making operations in this region dangerous and challenging from a planning perspective. The opening of the Arctic may also create territorial disputes and competition for resources among the countries in the arctic region.

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New Risks of Aquatic Invasive Species

Invasive species are non-native species whose introduction to an ecosystem causes, or is likely to cause, environmental damage, economic loss, and/or harm to human health. Many invasive species are introduced by hitching rides on ship hulls or from the ballast tanks that are used to balance ships in the water. Growth in marine traffic through the arctic region as a result of decreased sea ice cover increases the potential for invasive species to be introduced. Also, warming oceans will create environmental conditions more favorable for many introduced species that may not previously have been able to survive in arctic waters. Learn more about invasive species in Alaska.

Increased Threat to Livelihoods and Cultural Values of Alaska Natives

Less sea ice along the coastline and flooding from melting glaciers and land-based ice sheets has increased the amount of coastal erosion, and threatens the stability and survival of many Alaska villages.

Also, Alaska Natives rely nutritionally, economically, and culturally on fish, marine mammals, and other wildlife for their livelihoods. Many coastal communities use sea ice as a platform for hunting and fishing, as a travel corridor along the coast, or as a drifting site to process animals. Changes in sea ice extent and ice type have made hunting and fishing more dangerous due to unpredictable ice conditions. Hunting and fishing have also become more difficult as marine mammals and fish adapt to less sea ice and change their distribution or migratory patterns, or decline in overall abundance. However, changing ice conditions may have the potential to increase access to some species of marine mammals as ice retreats, as suggested for the increased number of catches of narwhals in Greenland.

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Loss of Critical Habitat for Ice-Dependent Species

Many species of marine animals rely on sea ice for breeding, birthing, molting, feeding, and resting, such as ice-dependent seals, walrus, polar bears, and marine birds. Reduction in sea ice extent has caused these animals to alter their feeding, mating, and migratory patterns. For some species, changes have resulted in poor body condition and will likely alter further as sea ice continues to decline.

Walrus feed on organisms on the ocean floor, typically in shallow water. They use the sea ice edge as a platform to rest and dive from while foraging. As the ice edge retreats to deeper water, the walrus can no longer use that ice edge for foraging because the deeper water is not as productive and it becomes harder to reach the organisms they feed on. As a result, more walrus gather on shore in summer to gain access to productive shallow waters. However, this has caused an increase in the number of walrus aggregated in small areas, raising the risk of disease transmission among animals. When other animals, humans, or planes disturb the dense walrus group they can become startled and retreat into the water, which may lead to trampling of the smaller young walruses. Learn more about walruses and sea ice.

Polar bears are dependent on sea ice for breeding, resting, and hunting prey, primarily seals. They access seals from the sea ice surface. With less sea ice, there are fewer hunting opportunities for polar bears in Alaska, and obtaining enough food to survive becomes difficult. Scientists have observed population declines, changes in distribution and behavior, and worsening body condition in some polar bear populations. Research is ongoing to understand just how sea ice loss is affecting polar bear movements, diet, and survival, to better predict future changes. Learn more about polar bear–sea ice relationships.

Ice-dependent seals, such as ringed, ribbon, and bearded seals, depend on sea ice to give birth, nurse their pups, molt, forage, and rest. Arctic warming has caused spring break-up of the ice to come earlier in the season than normal. This prematurely separates pups from their mothers and exposes the young seal pups to the elements and predators before they may be ready. The disappearance of sea ice is also predicted to cause changes in distribution, and declines in abundance, of ice-dependent seals. This could have cascading effects on the arctic food web. Ringed seals are the most important source of food for polar bears, which are having a harder time hunting due to reduced sea ice. There is concern that ice-dependent seals may not adapt well when sea ice declines to the point where they are forced to haul out on land for life functions that were previously carried out on ice.

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Changes in Timing and Location of Algal Blooms

Algal blooms in arctic seas are tied to sea ice conditions. Ice-algae blooms occur on the underside of the ice and, along with open-water phytoplankton blooms, contribute to the base of the arctic marine food chain. Algae directly support zooplankton and fish, and indirectly support fish, seabirds, and marine mammals such as bowhead whales. Changes in sea ice thickness and abundance can affect the timing, location, and extent of algal blooms. Reductions in summer ice may cause increased phytoplankton blooms, which could then drive greater zooplankton production if the timing of the peak zooplankton grazing periods aligns with phytoplankton blooms.

Many questions remain as to how a more productive and open-water Arctic Ocean may impact food webs. The potential is recognized for serious impacts on species further up the food web due to altering abundance, distribution, feeding patterns, and survival of arctic algae. These impacts could result in significant economic repercussions on commercial fisheries for crabs and fish, and subsistence fisheries for shellfish, fish, and marine mammals. However, predicting exactly how algal blooms will change is difficult and there is the potential that some species may actually benefit from changes in the timing and location of algal blooms. More research is needed to understand the complex relationship among sea ice, algae, and the arctic ecosystem.

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Arrigo, K.R., et al. 2012. Massive phytoplankton blooms under arctic sea ice. Science 10.1126/science.1215065 (

Søreide, J.E., E. Leu, J. Berge, M. Graeve, and S. Falk-Petersen. 2010. Timing of blooms, algal food quality and Calanus glacialis reproduction and growth in a changing Arctic. Global Change Biology 16:3154-3163 (

Changes in Species Range and Abundance

Changing water temperatures are predicted to alter the abundance and location of many marine species, including commercially important species, those used as food by other animals, and those used for subsistence. As temperatures increase, species may change their habitat ranges, moving northward. When organisms change their range and move into a new habitat the move can:

Species from farther south have already been observed moving northward to Alaska. Higher temperatures and reduced sea ice may increase the viable range for important fish species such as cod, herring, and pollock. However, warming water could reduce abundance of these species in their current range, diminishing fisheries. In addition, moving northward may mean moving to a less hospitable habitat for some species, reducing their survival. Fish and shellfish have a specific temperature range in which they can survive. Species can move northward to stay within that temperature range as waters warm, but only to an extent. In Alaska, species don’t have very much room to move farther north. Coldwater species, especially in Alaska, may not have a cooler habitat to move to, and may either adapt to warmer temperatures or perish.

Often, climate influences key life-events for organisms, including migration, mating, and birth. As temperatures have increased in recent decades, the timing of these events has changed for some species. Changes in the timing could lead to mismatches in the timing of migration, breeding, and food availability. For example, if fish, birds, or marine mammals change their migration patterns, they may arrive at a time when food availability is not optimal, leading to poorer body condition and/or reduced survival. Warming ocean temperatures could also change the timing and location of fish runs, creating the need to change fishery management plans.

Changes in Weather Patterns at Mid-Latitudes

The continuing loss of arctic sea ice and rising ocean temperatures may dramatically alter global weather and precipitation patterns. Warmer temperatures over the poles may weaken the jet stream, causing weather systems to progress more slowly, potentially increasing the chances for more extreme weather events such as droughts, floods, and heat waves. Rising arctic temperatures are predicted to bring more precipitation to the Arctic, and cause more frequent and intense droughts over the US Lower 48 and other middle latitudes. This is a new area of research, and making predictions is difficult due to the complexity and wide variability in the arctic atmosphere and sea ice.

Increased Coastal Erosion and Flooding

Rising ocean temperatures are causing sea ice to become thinner and less extensive, creating more open water and allowing stronger wind-driven wave action. Delayed arrival or the loss of shore-fast ice during the fall storm season exposes the coast to direct wave action. Stronger waves and frequent storm surges are increasing the rate of coastal erosion along arctic shores. Increased ocean temperatures can result in more rapid erosion in permafrost-rich coastal areas, such as along the North Slope of Alaska where the most rapid increases in erosion rates have been observed.

Coastal erosion is further accelerated by rising sea levels in some parts of Alaska. As ocean temperatures rise, the water expands and this contributes to rising sea levels. The melting of arctic sea ice will not cause the sea level to rise appreciably because the sea ice is already floating in the ocean. But as land-based ice sheets and glaciers melt, the sea level rises and increases the risk of flooding in low-lying areas. Researchers say that glacial melt worldwide accounted for 30% sea-level rise between 2003 and 2009.

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