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Are Polar Bears on Thin Ice?

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By: Kaylie Anne Costa, SRC Intern

When you think of polar bears what comes to mind? Is it a mama bear and a cub struggling to swim miles to find a piece of sea ice? Because that is exactly what is beginning to occur in the Arctic. With the rise of the sea surface temperatures, more and more sea ice is thawing causing the polar bears breeding and hunting grounds as well as means for transportation to disappear.

Figure 1: Polar bears using sea ice for transportation (By NOAA Photo Library – anim0115, Public Domain, https://commons.wikimedia.org/w/index.php?curid=17942736)

Polar bears have a varied diet consisting of seals, birds, fish, whales, and other marine resources. They also utilize a mixture of hunting methods. For example, polar bears may stalk seals in the open ocean or sneak up on seals that are drifting on sea ice. When there is not sea ice, polar bears must rely much more heavily on their swimming skills for transportation and hunting.

In a recent study, Lone et. al (2018) studied the time that female polar bears spend in the water to gain understanding as to how polar bears might react to future decreases in Arctic sea ice. 57 adult polar bears were tagged with devices to gather data on their locations, the amount of time spent swimming, and the diving depths. This study showed that polar bears’ choice of hunting strategies, and therefore amount of swimming, greatly depends on the individual. In addition, environmental factors and if the females had cubs also impacts the time a polar bear spends swimming. Polar bear cubs lack the thick layer of fat that insulates their bodies leaving them more susceptible to hypothermia. As a whole, the main variable that influence the swimming behaviors of the polar bears was the seasonal variation in sea ice. The most swimming occurred in summer and fall with less swimming occurred during the winter and spring. Modeling techniques were also used to correlate increased swimming with decreased levels of sea ice.

Figure 2: Polar bear swimming (https://commons.wikimedia.org/wiki/File:Polar_bear_arctic.JPG)

Overall the polar bears appeared well adapted to arctic marine environments and were able to complete long distance swims and dive greater than 10 meters. As sea ice continues to disappear, more polar bears will be required to alter their choices of hunting strategies to adapt to the new environment. This study shows promise in polar bears’ ability to adapt to reduced sea ice, at least to a certain extent. Further studies will need to be completed to analyze the impacts that additional swimming behavior will have on the polar bears health overall.

Works Cited

Lone, K., Kovacs, K. M., Lydersen, C., Fedak, M., Andersen, M., Lovell, P., & Aars, J. (2018). Aquatic behaviour of polar bears (Ursus maritimus) in an increasingly ice-free Arctic. Scientific reports, 8(1), 9677.

Impact of Multiple Stressors on Sea Bed Fauna in a Warming Arctic

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By: Brenna Bales, SRC Intern

The Arctic Ocean has been a heavily monitored area in recent years as climate change continues to affect the planet. This area is at high risk due to the fact that is has warmed at almost twice the rate as the rest of the planet in recent decades causing a decrease in sea-ice cover, glacial volume, and increases in temperature and precipitation (Hassol and Corell 2006). The Barents Sea is particularly vulnerable to climate change as it is experiencing the greatest temperature increases throughout the Arctic and may soon become an Atlantic-dominated climate region with warm and well-mixed waters, further preventing sea ice formation (Lind et al. 2018). Jørgensen et al. (2019) examined the Barents Sea benthic (seafloor) composition and how it has been affected by several stressors relating to climate change. Ecological impacts among the benthic environment were examined as a result of seawater warming, bottom trawling, and predation from a new, invasive predator: the snow crab (Figure 1).

Figure 1: Two snow crabs along the seafloor, a larger male above and a smaller female below. Image Credit: Derek Keats, Johannesburg, South Africa

The study characterized the vulnerability of different invertebrate groups when affected by these three variables across a predefined grid consisting of 36 x 36 nautical mile cells in the Barents Sea (Figure 2). Firstly, sensitivity to seawater warming between 2009-2011 (colder period) versus 2012-2015 (warmer period) was investigated. Both species temperature indices (a measure of the average temperature experienced by individuals across a species’ range) and community temperature indices were calculated by combining temperature values with information about the seafloor organism distribution. Secondly, species vulnerability to bottom trawling (Figure 3) was characterized by a species’ morphology, mobility, and body size. Slower, larger, and taller animals were categorized as having a larger susceptibility to trawling effects, whereas quicker, smaller animals would be more resilient. Lastly, the predatory effects of the invasive snow crab were quantified by number of prey items and annual biomass (amount of prey) consumed.

Figure 2: Geographic location of the Barents Sea with the 2280 sampling locations from the present study (Jørgensen et al. 2019).

Figure 3: Depiction of the practice of bottom trawling (Source: NOAA.gov).

From the initial, colder period (2009-2011) to the latter, warmer period (2012-2015), there was an increase in organisms with warm-water affinities and a reduction in those with cold-water affinities. While the overall sensitivity to temperature of the communities decreased with time, areas that were further north into the Arctic showed a higher vulnerability to temperature changes than more southern areas continuously experiencing warming waters. The sensitivity to trawling was lowest in the center region of the Barents Sea and increased toward outer regions. Lastly, the sensitivity to snow crab predation was highest along the northwestern border connecting to the southeastern border of the study area. Overall, the northwestern area of the Barents Sea was found to be the most vulnerable area when all three variables were combined. In conclusion, the combination of multiple stressors in any particular area can have severe consequences on the resilience of a local community to change. Management in the form of closed areas or gear modification is thus highly recommended by researchers from this paper to lessen the threats that these communities, especially those of the northwestern Barents Sea, are facing.

Work Cited:

Hassol, S.J. and Corell, R.W., 2006. Arctic climate impact assessment. Avoiding dangerous climate change, p.205.

Jørgensen, L.L., Primicerio, R., Ingvaldsen, R.B., Fossheim, M., Strelkova, N., Thangstad, T.H., Manushin, I. and Zakharov, D., 2019. Impact of multiple stressors on sea bed fauna in a warming Arctic. Marine Ecology Progress Series, 608, pp.1-12.

Lind, S., Ingvaldsen, R.B. and Furevik, T., 2018. Arctic warming hotspot in the northern Barents Sea linked to declining sea-ice import. Nature Climate Change, 8(7), p.634.

Cetacean Species Affected by Warming Arctic

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By Hannah Armstrong, RJD Intern

Global climate change, among other anthropogenic issues, is becoming an increasingly significant threat to the Arctic region of the world.  Specifically, higher average temperatures and rapidly disappearing sea ice are of conservation concern for ice-dependent species.  Arctic marine mammals are specifically adapted to take advantage of the climatic conditions that have prevailed in the Arctic for millions of years, and have been a target of conservation based on their role in the functioning of Arctic ecosystems and surrounding communities.  Despite these conservation concerns, with impacts of climate change likely to worsen in coming decades, there is increased industrial interest in Arctic areas previously covered by ice.

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A graph showing the evident decline in average monthly arctic sea ice extent from September 1979 through 2012 (Reeves et al).

In a recent study, scientists observed and mapped the distribution and movement patterns of three ice-associated cetacean (marine mammal) species that reside year-round in the Arctic: the Narwhal (Monodon monceros), Beluga (white whale, Delphinapterus leucas), and Bowhead Whale (Balaena mysticetus) (Reeves et al. 2013).  Then they used these ranges and compared them to current and future activity sites related to oil and gas deposits, exploration, development and commercial shipping routes, to assess areas of overlap, as a means of highlighting areas in the Arctic that might be of conservation concern.  Some of the results indicated the sensitivity of Bowhead whales to industrial activity; the sensitivity of Narwhals to climate change and noise, as well as a shift in distribution due to ice conditions; and the sensitivity of Beluga whales to noise, as well as a wider distribution extending into the sub arctic (Reeves et al. 2013).  These observations ultimately triggered the need for a better understanding of the implications of environmental changes in the Arctic for cetacean species, in order to develop effective conservation and management policies (Reeves et al. 2013).

Poorly documented shipping routes and operations, in addition to accelerating Artic pressures in Arctic Norway, Arctic Russia, the Alaskan Arctic, Arctic Canada and Arctic Greenland, indicate that immediate measures need to be taken to mitigate the impacts of human activities on these Arctic whales, as well as the people who depend on them (Reeves et al. 2013).  As indicated by researchers, some of these measures include: careful planning of ship traffic lanes (re-routing if necessary) and ship speed restrictions; temporal or spatial closures of specified areas (e.g. where critical processes for whales such as calving, calf rearing, resting, or intense feeding take place) to specific types of industrial activity; strict regulation of seismic surveys and other sources of loud underwater noise; and close and sustained monitoring of whale populations in order to track their responses to environmental disturbance (Reeves et al. 2013).

After comparing maps of Arctic whale ranges with maps of recent and anticipated oil and gas activity and shipping traffic in the Arctic, researchers noticed the unquestionable overlap between Arctic whales and harmful human activities.  Based on unparalleled current and predicted rates of climate change, the futures of these three Arctic whale species are uncertain.  Based on the significance of these species, both culturally and for proper functioning of the Arctic ecosystem, well-informed management decisions related to human activities will be imperative going forward.

 

Reference:

Reeves et al.  Distribution of endemic cetaceans in relation to hydrocarbon development and commercial shipping in a warming Arctic.  Marine Policy 44 (2014).

“Narwhals Breach.” WikiMedia Commons. WikiMedia, 1 Oct. 2012. Web. 29 Jan. 2014.