







Even though it has the lowest population density, Alaska is the largest US state. Despite experiencing little human activity historically, climate change is still leaving its mark on this pristine expanse. In this post I will focus on how climate change is affecting Alaska’s weather patterns, flora and how it will continue to do so in the future.









How is Alaska’s climate changing?





Alaska on average has warmed by 3°F (1.7°C) over the course of the last 60 years, which is nearly double of the global average since 1880. Average winter temperature rise is at 6°F (3.3°C), which is having a huge impact on local ecosystems (Figure 1).

















Firstly, I would like to consider how climate change is manifesting in contrasting ways in different parts of the state. For instance, in Northern Alaska , winter airflow intensified, reducing snowfall. Here, spring snowmelt is also occurring at a faster rate because the flow of warm most air from the West has increased.





On the other hand, in South-Central Alaska the story is different; here due to warming of the Pacific Ocean, the low-pressure system intensified, leading to increased precipitation–including snowfall– by 49% since the 1850s.





This highlights the importance of taking into account the size of Alaska and the need for scientists and policy makers to consider how climate change will affect its different regions.









How is productivity changing?





Many scientists are predicting how climate change will affect Alaska’s ecosystems. While the majority agree that shrubland will encroach into the tundra, they have different theories on whether productivity will increase or not.





For example, a study conducted in the Kuparuk Basin investigated the role increased snowfall will play in enhancing productivity through a positive feedback mechanism. In their view, the expansion of shrubland will allow more snow to be trapped in a given location, increasing the snowpack’s thickness. Therefore the ground is insulated and kept warmer, allowing microbial activity in the soil to flourish. Soil nutrients thus increase, further promoting the growth of shrubland (Figure 2). However, their theory relies on a constant supply of snow, which may not occur in some areas if climate change is altering weather patterns.

















Nevertheless, other studies have shown that winter warming is increasing both air and soil temperatures anyway. The ‘Carbon in Permafrost Experimental Heating Project’ (CiPEHR) found just this near Eight Mile Lake. In their 2011 study , soil temperature has increased by 4.1°F (2.3°C) from 2010, along with the depth at which microbial activity was viable due to the thawing of permafrost. This has resulted in a 20% increase in biomass.





Nonetheless, in cases it has been reported that despite the lengthening of the growing season, productivity does not necessarily increase. Other factors such as nutrient availability –which is low in tundra regions- may act as a limiting factor and prevent a sudden increase in biomass. Indeed, a study has demonstrated that tree line advance is more dependent on nutrient availability than temperature. Trees are much larger than shrubs, meaning they need more nutrients to survive. While this may not be possible in the impoverished soils of the tundra at the moment, their nutrient content may increase in in the future due to the reasons outlined above- though, this process may take a couple of years to manifest in the landscape.





Research has also considered how the types of shrubs growing in the Alaskan tundra may change due to the changing climate. Woody shrub species from the genera Betura and Salix are predicted to increase in range as they are well adapted to higher temperatures and longer growing seasons. However, evergreen shrub species such as Cassiope tetragona do not capitalise on the growing season starting earlier, meaning that they are being out-competed.









What can limit future growth?





Despite the evidence of warming promoting growth in the tundra, climate change may also threaten it.





As I mentioned in a previous blog post , increased temperatures may encourage the northward shift of pine beetle epidemics . This threatens Alaska’s forests and in turn increases the risk of wildfires due to higher fuel availability.





In addition, early season frost may threaten species that flower early. It could have a detrimental impact on other organisms -such as pollinators - that rely on them for their existence.





Finally, as mentioned earlier, some parts of Alaska are receiving less precipitation. This will create drought conditions , which will prevent plants from capitalising on the longer growing season and increased nutrient availability.









What can we conclude?





So what's the take away from this post? We need to appreciate Alaska’s vastness, meaning the acknowledgement that different parts of the state will respond to climate change in very diverse ways. Nutrient availability will increase in the future, promoting the growth of shrubland. On the other hand, it is not clear how reduced precipitation in some parts of Alaska and increased risk of wildfires will impact the state’s flora.













@tomicserep





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