Any Reason to Expect a Tipping Point with Arctic Sea Ice?

by Emil Morhardt

Williamson et al. (2016) examined the satellite data looking for signs of a tipping point in Arctic sea ice loss, but found none (my Jan 1 post). About the same time, Notz and Stroeve (2016) looked at the same data and did a simple linear correlation between September Arctic sea ice area and cumulative CO2 emissions since 1850. Voila! There was a strong negative linear correlation between the two showing a sustained loss of 3 ± 0.3 square meters of September sea ice area per cumulative metric ton of CO2 emission. Their title summarizes the result clearly: Observed Arctic sea-ice loss directly follows anthropogenic CO2 emission. If this linear trend continues and there is no tipping point—and there is no reason to expect one—we can make a pretty good guess about the timing of the future of Arctic sea ice to the extent we can predict CO2 emission levels. At the rate we are going, September Arctic sea ice will be completely gone before mid-century (and global average temperatures will have risen more that 1.5ºC.) Furthermore, we can now get a feeling for how much our personal use of fossil fuels and the energy derived from the directly affects Arctic sea ice; the average CO2 release from personal use is several metric tons,  Continue reading

Environment and Politics: Alaskans Adapt to a Changing Climate

by Russell Salazar

While climate change mitigation must continue, societies are marching on into an inevitably warmer world. The ability for a community to adapt to a new environment will be a crucial characteristic in the coming century. Wilson (2013) presents a study of an Alaskan village to show how political and social changes are correlated with a community’s vulnerability to the impacts of climate change. The paper focuses on the subsistence livelihoods of the Koyukon Athabascan people, describing major changes since the 1950s that altered their climate adaptability. These included an increased emphasis on formal education, a greater exposure to market economies, as well as the legislation and bureaucracy introduced by the government, all of which had a profound impact on the Koyukon Athabascan way of life. Wilson concludes by encouraging more cautious and deeper ethical considerations with regard to placing political constraints on communities. Continue reading

Climate Change and its Effect on Alaskan Inuit Populations

by Margaret Loncki

Ford et al. (2008) explore the vulnerability of two populations of Alaskan Inuits to climate change. The authors begin by explaining the cultural importance of the “procurement, sharing, and consumption” of traditional food. Global climate change plays a very important role in these Alaskan Inuit’s ability to efficiently and successfully harvests viable food sources. As a result, Climate change has the potential to bring about social, cultural, and economic change. Continue reading

Arctic Warming and the Atlantic-Pacific Fish Interchange

by Kyle Jensen

For most of the Quaternary Period the inhospitable environment north of the Arctic Circle has served as a biotic barrier between Northern portions of the Atlantic and Pacific oceans. Through it is known that interchange across the Northwest and Northeast passages has occurred, currently only 135 of over 800 fish species found above 50° of latitude are found in both oceans. Continued warming may result in the reopening of these passages resulting an accelerated interchange of species between the Atlantic and Pacific as species follow favorable conditions into higher latitudes. This may also lead to increased movement of fishing and shipping vessels through these channels, which could facilitate further interchange. This has the potential to impact the food webs and biodiversity of systems in both of these oceans, the consequences of which would affect ecosystems currently comprising 39% of global marine fish landings. To analyze potential impacts of future species interchange, Wisz et al (2015) has made forecasts of potential distributions for 515 fish species. Continue reading

Modeling CO2 and CH4 Fluxes in the Arctic using Satellite data

by Rebecca Herrera

The peatlands and tundras of the Arctic perform vital ecosystem services to the earth through their ability to sequester carbon (CO2) and methane (CH4) and function as a carbon sink. The ability of the permafrost in the peatlands and tundra ecosystems of the Arctic to continue to function as a natural reservoir for carbon and methane may be disrupted by rising global temperatures that increase the rate of soil decomposition. Watts et al. (2014) integrate a terrestrial carbon flux (TCF) model to include a newly developed CH4 emissions algorithm. The new TCF model simultaneously assesses CO2 and CH4 fluctuations and the corresponding net ecosystem carbon balance (NECB), which is contingent upon gross primary productivity (GPP) subtracted from ecosystem respiration. The integrated TCF model uses data gathered through satellite remote sensors to assess fluxes in CO2 and CH4. Continue reading

Red Fox Populations Encroach on Arctic Fox Ranges due to Warmer Temperatures

by Hilary Bruegl

In the nineteenth century Arctic tundra of Finnmark, Norway, the Arctic fox population declined to near extinction and have been recovering minimally despite strict protection. Hamel et al. (2013) investigated potential factors involved in suppressing healthy recolonization of prior territories, including encroaching red fox populations and variation in prey availability. By baiting and periodically photographing the area, the authors found red foxes to be the most important influence on the Arctic fox population in northeast Norway. Not only are red foxes more comfortable in the warming temperatures of the tundra, but there has also been a significant reduction in fox hunting, allowing the red fox population to flourish. Rodent population fluctuations were first documented alongside fox populations as a limiting factor of population growth; however, they had fewer effects than either land cover changes or red fox infiltration. Continue reading

Greenland Warming at Last Deglaciation: the Younger-Dryas Not So Cold

by Emil Morhardt

I’ve been blogging recently about papers that claim the thousand-year cessation of global warming in the midst of the last deglaciation—known as the Younger-Dryas (Y-D)—was triggered by a comet. Buizert et al.’s (2014) paper on Y-D temperature changes doesn’t address the comet question, but another equally interesting one: why did the sudden reversal of temperature 12,800 years ago (whatever it was triggered by) cause the temperature to plunge clear back to what it was before any warming had started? That’s what the relative deuterium and oxygen-18 concentrations from the Greenland Ice Sheet ice cores imply—more about that in a moment. Nevertheless, it seemed unlikely because at the time of the Y-D, a considerable amount of CO2 had accumulated in the atmosphere and Antarctica was warming apace. The answer, according to this paper is that temperatures did not cool down so much after all; things cooled off for sure, and warming was delayed for another thousand years, but at the depth of the Y-D cooling most of Greenland was on the order of 4˚C warmer than it had been 4,000–5,000 years before—but still quite cold. Continue reading

Reduced Ice and Polar Bears in Beaufort and Chukchi Seas

by Hilary Bruegl

Polar bears in the Arctic rely on sea ice as a means of locating and hunting for seals, their primary food source. Because populations of polar bears can be quite variable, their responses to climate change also depend on reproductive and hunting strategies employed by each population, especially when faced with declining sea ice. The Chukchi Sea (CS) population of polar bears was found to have greater body size and overall condition in a period of four years between 2008–2011 as compared to previous CS population data from 1986–1994 as well as compared to the 2008–2011 Beaufort Sea (SB) population of polar bears (Rode et al. 2014). The SB population of polar bears has been exposed to declining sea ice conditions for longer periods of time than the CS population, allowing for compounding effects over generations, which may account for some Continue reading

Atmospheric and Advective Forcing will affect the Physical and Biological Properties of the Barents Sea

 Between 2005 and 2008, the Norwegian Component of the Ecosystem Studies of Sub-Arctic Seas (NESSAS) studied atmospheric and advective forcing on the Barents Sea using retrospective analysis and modeling.  Atmospheric processes such as the North Atlantic Oscillation (NAO) and seasonal cyclones affect temperature and salinity in the Barents Sea.  Advection from the North Atlantic and surrounding Sub-Arctic seas also affects temperature and salinity. (Drinkwater 2011)  These variables in turn determine the sea-ice extent.  There is a corresponding affect on fisheries and primary production. Positive NAO, a greater number of cyclones, and advection of warmer water produce a warmer Barents Sea with less sea-ice. (Drinkwater 2011)  This leads to increased primary production and greater fisheries.  Additionally, in a warmer climate spawning sites will shift, fish populations will expand or retreat northward, and maturation will be faster. (Drinkwater 2011)   These effects were compared to other seas at similar latitudes to the Barents Sea. Many similarities in responses to forcing and overall biological processes were observed.  NESSAS recommends that further studies be carried out to better determine the effects of climate change on Sub-Arctic seas. —Katherine Recinos         
Drinkwater, K., 2011. The influence of climate variability and change on the ecosystems of the Barents Sea and adjacent waters: Review and synthesis of recent studies from the NESSAS Project. Progress in Oceanography. 90, 47-61.

The NESSAS program, as previously mentioned, was the Norwegian version of the more regional Ecosystem Studies of Sub-Arctic Seas (ESSAS) program.  The goals of both programs were the same; to examine how forcing, especially climate processes, effect physical oceanography, to look at how change affects marine ecosystems, and to see within those ecosystems how variability affects productivity and fish stocks.  The results could be used to combat future climate change.  The Norwegian program also compared the Barents Sea to other Arctic and Sub-Arctic seas.
                                                                                                          
Drinkwater begins with an overview of the NESSAS results.  Researchers looked at the NAO which has both a positive and negative phase.  During the positive phase, strong winds and storms blowing westward carry warm air and Atlantic water into the Barents Sea.  During the negative phase, the winds are weaker; cold air and less Atlantic water are carried into the Barents Sea.  The result is that positive phase NAO means higher sea temperatures in the Barents Sea and negative phase NAO means lower sea temperatures.  Sea temperature affects how much ice forms and when it forms and melts which has important ecological consequences.  
The NAO is associated with North Atlantic and Arctic cyclones.  The NESSAS studies investigated the patterns of cyclones that affect the Barents Sea.  An annual correlation was found between times of more intense Arctic cyclones and greater sea-ice cover.  However, longer term sea-ice extent was determined by North Atlantic cyclones with a one to two year lag from presence of cyclones to noticeable effects on sea-ice.  These effects are caused by the cyclones transporting different temperature waters into the Barents Sea. 
A different type of forcing is moisture flux which controls the amount of freshwater input from rivers, runoff, and precipitation.  Cyclones in northern latitudes play a role in moisture flux in Arctic and Sub-Arctic oceans and seas.  Seasonal variability affects the influence of the cyclones on moisture flux; there is a greater link between moisture flux and cyclone activity in the spring, summer, and autumn.  Atmospheric pressure patterns which produce cyclones and storms may also be changing.  The Arctic/North Atlantic Oscillation (AO/NAO) pressure pattern used to have three centers of action but now has only two more northerly centers.  This is leading to less atmospheric forcing and therefore a warmer Arctic overall.  
Drinkwater then discusses the effects of advection on the Barents Sea.  Not only does advection have the power to bring water of different temperature and varying salinities to the Barents Sea, it can also carry phytoplankton, zooplankton, and fish larvae to the Sea.  Several studies were carried out as part of NESSAS to try and figure out what factors determine advection, and how advection specifically works on the Barents Sea and surrounding oceans.  There are a series of differing salinity water masses known as the Great Salinity Anomalies (GSAs) which are either negative or positive anomalies.  A gradient across the northwest to northeast Atlantic controls their movements.  Due to advection, these water masses can affect Arctic waters and their respective salinities which affect, among other things, sea-ice formation.  Other studies used moors to monitor the flow of water into the Barents Sea.  This advection is important because it has major effects on the temperature of Barents Sea water, including heat fluxes.  It is affected by cyclones, storms, seasonal variability, and the NAO.
The NESSAS study also looked at biological effects.  The NORWECOM model, a coupled 3-D physical, chemical, and biological ocean model was used to examine primary production.  The North Atlantic coastal waters and the waters off the coast of Norway had the highest primary production.  Variability in primary production over the years was stated to be caused by the NAO.  When the NAO is high, there is more mixing, a greater concentration of nutrients, and therefore greater production.  When the NAO is low, the opposite is true.  Researchers investigated the future of fish stocks by looking at past data on fish populations.  A period of climate variability, the Atlantic Multidecadal Oscillation (AMO), produced a warming period in the 20thcentury that resulted in greater numbers of fish, northward spread of fish populations, changes in spawning areas, changes in timing of spawning, and faster growth and development for many cold-water species (ex. cod).  It also caused an increase in primary production which helped increase fish abundance. 
Drinkwater lists the results of comparative studies undertaken by NESSAS.  The Barents Sea is experiencing similar effects from atmospheric forcing as other seas at similar latitudes and would be similarly affected by climate change.  Many of the trends noted in the Barents Sea were also seen in other seas including advections affect on salinity and temperature, relationship of sea-ice to primary production, and spread of fish northward as temperatures increase. 
The NESSAS study admits uncertainty where climate change is concerned.  If warming continues, there could be a multitude of effects on fisheries, including increased yields.  For example, one study showed that capelin (a small fish) spawning sites would move further north and east in the Barents Sea.  The effects of climate change on physical properties of the Barents Sea could be mitigated by conflicting atmospheric processes such as the AMO and AMOC which could bring colder, saltier waters to the Arctic and Sub-Arctic.      

Artic Ecosystems Response to Climate Change

Sea ice conditions are an important factor in the health of many arctic mammals use the sea ice to breed and to carry out many social behaviors.  The harp seal is one of those species, using the sea ice as a substrate for pupping and nursing its young.  Johnston et al. (2012) examined the impact of decreased sea ice on harp seal mortality. The scientists used Northern Atlantic Oscillation (NAO) data to represent climate change; NAO is the dominant pattern in climate variability in the North Atlantic. The breeding regions that Johnston et al. used were located in the Northeastern US, the Gulf of St. Lawrence, and the White Sea near Norway.  Using the NAO data, sea ice measurements, and recorded mortality rates of deal harp seal pups, the authors established a relationship between decreased sea ice ice/poor NAO conditions and increased mortality in young harp seals. They also established a link between NAO conditions and sea ice cover. Johnston et al. suggest that the harp seal is stable at the moment, but could be harmed by the cumulative effect of human influences and rapid climate change. –Connor O’Boyle
            Johnston, D., Bowers, M., Friedlaender, A., Lavigne, D., 2012. The effects of climate change on harp seals (Pagophilus groenlandicus). PLoS One 7, e29158.

Johnston et al.studied the effect of climate change on harp seals in three ways.  They examined the differing sea ice levels in the Gulf of St. Lawrence with neonatal mortality rates in harp seals in the Northeastern US. The authors linked NAO conditions to differing sea-ice levels and did a retrospective cross-correlation analysis of NAO conditions and sea ice in two breeding regions of harp seals. Lastly they showed the relationship between NAO conditions and sea ice by doing linear multiple regression models that accounted for short-term variation in ice driven by the NAO.  In order to link reductions in sea ice cover and seal mortality the scientists used mortality data for dead harp seals and compared that with sea ice cover data from the Gulf of St. Lawrence during the same time period. For the retrospective analysis of NAO conditions and sea ice the authors looked at two breeding regions of harp seals, the Gulf of St. Lawrence and White Sea region. The authors compared these two areas within a retrospective assessment of published harp seal neonatal mortality data. They conducted a wider investigation using two addition breeding regions from Newfoundland and the Greenland Sea. This second investigation was used to assess longer-term trends in sea ice cover across the entire North Atlantic.  Johnston et al. used sea ice data obtained from the National Sea Ice Data Centre and NAO data from the National Center for Atmospheric Research.
            The results showed that sea ice and seal mortality were significantly correlated.  Lighter ice conditions were linked with increased numbers of stranded dead seals. The regression model between NAO data and seal mortality showed a similar relationship. Breeding regions in the White Sea and the Gulf of St. Lawrence showed significant differences in sea ice cover and NAO data. In the White Sea heavier ice coverage was seen during negative NAO periods and lighter ice coverage was seen during positive NAO periods. The western North Atlantic ice conditions were opposite with heavier ice coverage during positive NAO periods and lighter ice coverage during negative NAO periods. The results from their mixed effects models revealed a statistically significant annual decline of sea ice cover in all four breeding regions, regardless of variation in NAO conditions.
            The negative relationship between sea ice coverage and seal mortality rates shows how climate change is having an impact on seal populations. The scientist’s regression revealed that an increase in first year mortality occurred in years with lighter sea ice coverage and lower NAO index values. This also shows how the NAO determines sea ice dynamics in harp seal breeding regions. The retrospective analysis of NAO conditions revealed that the NAO was consistently negative in light ice conditions in the Northwest Atlantic, and in years with less ice coverage the harp seal populations decreased significantly. The Northeast Atlantic breeding regions are out of phase with the NAO and the NAO was positive in times of decreased sea ice, years with decreased seal populations correlated to positive NAO indices and lower sea ice levels. The fluctuations of harp seal populations over time corresponds to increases and decreases in sea ice as well as the NAO indices, showing how climate change directly impacts sea ice levels, which then disrupt harp seal reproduction. The authors found that the ice cover in the breeding habitats for harp seals has been declining since 1979, and along with this the harp seal’s yearly mortality rate has gone up since 1979. Johnston et al. conclude their paper by stating that harp seals could be a vulnerable species in the future. The authors state that the harp seals are well suited to deal with natural shifts in climate however the cumulative effects of human influences such as hunting and global warming could put them at a higher risk. Other artic seal species could be at risk as well sharing many of the characteristics and breeding regions of the harp seal.