Papers already assigned (March/April):

Schuur et al. 2008. Vulnerability of permafrost carbon to climate change: Implications for the global carbon cycle. Bioscience 58, 701-714.

Parham et al. 2013. Permafrost and fire as regulators of stream chemistry in basins of the Central Siberian Plateau. Biogeochemistry

Sturm et al. 2005. Winter biological processes could help convert arctic tundra to shrubland. Bioscience, 55: 17-26

Olefeldt et al. 2013. Environmental and physical controls on northern terrestrial methane emissions across permafrost zones, Global Change Biology, doi: 10.1111/gcb.12071

Belshe et al. 2013. Tundra ecosystems observed to be CO2 sources due to differential amplification of the carbon cycle. Ecology Letters, 16: 1307–1315

 

Final paper assignment (May-July):

 Big Picture: The Polaris Project is focused on some really big questions and the readings below will help you think big: How much carbon is there in the Arctic? How does it move? How is the land surface changing? Could humans change Artic carbon and nutrient cycles with animal grazing?

• Cole et al. 2007. Plumbing the Global Carbon Cycle: Integrating Inland Waters into the Terrestrial Carbon Budget. Ecosystems 10, 171-184.
  • Efforts to understand global sources and sinks of atmospheric carbon dioxide have historically been focused on terrestrial and marine ecosystems.  Recent research suggests that freshwater ecosystems such as streams, rivers, wetlands, and lakes play important, yet overlooked roles in the flux of terrestrial organic matter to the atmosphere and world’s oceans.
• McGuire et al. 2010. The carbon budget of the northern cryosphere region. Current Opinion in Environmental Sustainability 2010, 2:231–236.
  • The sources and sinks of arctic carbon are uncertain but the scientific community is working diligently to improve these numbers! This paper outlines what we know and where we need to go. And if you want more check out McGuire’s 2010 monograph on this subject.
• Sturm 2010. Arctic Plants Feel the Heat. Scientific American May 2010,32-39.
  • This is a popular-science write up of how the terrestrial system changing in the Arctic. Fast, fun read.
• Zimov. 2005. Pleistocene Park: Return of the Mammoth’s Ecosystem. Science 308, 796-798.
  • Sergey Zimov is a remarkable scientist who “thinks big”.  This article provides an overview of one of his visions and the ongoing Pleistocene Park experiment.

 

Terrestrial:  While the Arctic is a tightly coupled system, research often tends to focus on either terrestrial or aquatic components.  As a group, we are working to strengthen linkages among our research—whether more terrestrial or aquatic in scope—and understand how our work fits into the larger integrated picture of the Arctic.  When reading these papers and developing your own projects, think about how processes and system components are connected.

• Bunn et al. 2007.Northern high-latitude ecosystems respond to climate change. Eos 88, 333–335.
  • A widely held assumption is that high latitude warming will cause increased photosynthesis in boreal forests. This paper calls some of those assumptions into question as it documents declining gross primary productivity in some boreal forest ecosystems.
• Chapin et al. 2005. Role of Land-Surface Changes in Arctic Summer Warming Science 310: 657-660.
  • Chapin and colleagues took a conceptual model of how the Arctic land surface functions in the global climate system and put numbers to the model. It’s an awe inspiring work.
• Loranty et al. 2012. Shrub expansion and climate feedbacks in Arctic tundra. Environ. Res. Lett. 7 011005 doi:10.1088/1748-9326/7/1/011005.
  • We know the Arctic land surface is changing. We know that shrubs are a huge part of it and we know that shrub cover mediates both the radiation budget and the carbon budget. This paper described some of how and what we know.
• Xu et al. 2013. Temperature and vegetation seasonality diminishment over northern lands. Nature Climate Change. doi:10.1038/nclimate1836.
  • Maybe Bunn et al got a little ahead of themselves. As the data roll in it appears that our understanding of taiga greening continues to change –  but that’s science.

• Knoblauch et al. 2013. Predicting long-term carbon mineralization and trace gas production from thawing permafrost of Northeast Siberia. Global Change Biology (2013) 19, 1160–1172, doi: 10.1111/gcb.12116.
  • What is going to happen as microorganisms get a crack at thawing permafrost? Respiration. But where, when, and how fast remain major question marks.
• Natali et al. 2014. Permafrost degradation stimulates carbon loss from experimentally warmed tundra. Ecology. http://dx.doi.org/10.1890/13-0602.1
  • Changes in vegetation—whether greening or browning—are important for carbon fluxes, but are only part of the story.  This paper examines whole ecosystem carbon dioxide exchange from a warming and thawing experiment during the growing season and in the winter.
• Väisänen et al. 2014. Consequences of warming on tundra carbon balance determined by reindeer grazing history. Nature Climate Change. 10.1038/NCLIMATE2147
  • Grazers are an important component of the Arctic System.  This paper examines interactions between warming, fertilization and reindeer grazing on tundra carbon balance.

 

River and Aquatic Carbon: In a largely roadless area, the rivers and waterways are the roads. It’s true for carbon and nutrients as well. These papers quantify how carbon and nutrients move and change as they move downstream.

• Frey and McClelland. 2009. Impacts of permafrost degradation on arctic river biogeochemistry. Hydrological Processes 23, 169-182.
  • There are many linkages between permafrost and river biogeochemistry. Over the next century there will be shifts in the river transport of organic matter, inorganic nutrients, and major ions, which might have critical implications for primary production and carbon cycling on arctic shelves and in the Arctic Ocean basin interior.
• Neff et al. 2006. Seasonal changes in the age and structure of dissolved organic carbon in Siberian rivers and streams. Geophysical Research Letters 33,L23401, doi:10.1029/2006GL028222.
  • This paper gets at some important questions relating to the age and origin of dissolved carbon in arctic rivers. Importantly, it shows that there is a switch during the year from modern to old carbon in the Kolyma main stem but the source of that old carbon is unclear.
• Walter et al. 2006. Methane bubbling from Siberian thaw lakes as a positive feedback to climate warming. Nature 443, doi:10.1038/nature05040.
  • Methane is a greenhouse gas that is many times more effective than CO₂ in trapping long wave radiation. This paper closes a critical gap in the methane budget by quantifying methane from lakes in Siberia.
• Vonk et al. 2013. High biolability of ancient permafrost carbon upon thaw. GRL doi: 10.1002/grl.50348.
  • This paper describes how some fraction of the carbon flowing past us in the Kolyma is ancient and available for exchange with the atmosphere.
• Mann et al. 2013.  Evidence for key enzymatic controls on metabolism of Arctic river organic matter. Global Change Biology. doi: 10.1111/gcb.12416
  • Permafrost thaw is mobilizing ancient organic carbon from terrestrial to aquatic ecosystems.  This paper examines the effect of nutrient and carbon composition on microbial enzyme activity.
• Schade et al. In Review. Variation in summer nitrogen and phosphorus uptake among Siberian headwater streams
  • This study examines the physical and biological processes that regulate movement of permafrost derived nutrients through Siberian streams that are draining both Pleistocene and Holocene-aged watersheds.