Research project: Ocean-Land Interactions at High Latitudes
|Figure 1. Reductions in terrestrial snow cover (blue) and sea ice (red) extent during June to August for the past since the 1960's and 1970's. 
Of all the regions in the world, the Arctic is perhaps the most sensitive to climate change, since air temperatures at high
latitudes have risen two to three times faster compared to the rest of the world [1,2,3]. This amplified temperature rise has
already led to apparent changes around the Arctic, such as reductions in snow cover, shown in Figure 1, an earlier onset of the
growing season  and permafrost degradation [5,6].
Next to these changes on land, the Arctic Ocean has also seen drastic and very apparent changes. Sea ice extent in the Arctic has
diminished by approx. 45000 km2/year , also shown in Figure 1, with an all-time low in 2007 [8,9], while at the same time
sea-ice thickness has decreased by ~50% in 40 years .
These changes in the ocean and on land are not isolated processes and in all probability influence each other. Recent studies have
suggested that the decline in sea ice has increased land surface temperatures , influenced weather patterns  and affected
plant growth in the Arctic .
From a carbon cycling perspective, this interaction between ocean and land is important since it is also expected to influence the
exchange of greenhouse gases in the Arctic. For example, an Arctic ocean with less sea-ice could lead to higher Arctic air temperatures and
changes in precipitation. Since methane emissions are sensitive to changes in temperature and water availability, this would subsequently
affect emissions. However, up till now no study has conclusively been able to confirm these connections, which have been obscured by a
lack of circumpolar measurements.
|Figure 2. (a) Globally averaged methane concentration. (b) Instantaneous growth rate for globally averaged atmospheric methane. Circles are annual increases 
Then again, there are studies that suggest that processes in the Arctic are directly linked to variations in the atmospheric
methane concentration [14,15] and ocean-land interactions might help in understanding and clarifying these patterns. For that
reason, the aim of my project is to assess how the mechanism of ocean-land interaction impacts greenhouse gas exchange in the Arctic,
with an emphasis on methane emissions.
To achieve this, a better understanding of the drivers of greenhouse gas exchange in the Arctic is needed. This research focuses on
observed and modeled changes in circumpolar greenhouse-gas exchange, and identifies signals that indicate influences from a changing ocean-land
interaction, in combination with the direct influence of sea ice on the greenhouse gas exchange of the Arctic Ocean. By zooming in on how a changing
sea-ice extent affects circumpolar greenhouse gas exchange, we will achieve a better understanding of the functioning of the system as a whole .
- Zwiers, F. W., Climate change - the 20-year forecast, Nature, 416 (6882), 690--691, 2002.
- Chapin III, F. S., et al., Role of land-surface changes in Arctic summer warming, Science, 310 (5748), 657--660, 2005.
- Serreze, M. C., and J. A. Francis, The Arctic amplification debate, Climatic Change, 76 (3-4), 241--264, 2006.
- Post, E., et al., Ecological dynamics across the Arctic associated with recent climate change, Science, 325 (5946),
- Christensen et al. Thawing sub-Arctic permafrost: Effects on vegetation and methane emissions. Geophysical Research Letters
(2004) vol. 31 (4) pp. L04501
- Schuur et al. Vulnerability of permafrost carbon to climate change: Implications for the global carbon cycle. Bioscience
(2008) vol. 58 (8) pp. 701-714
- Parkinson and Cavalieri. Arctic sea ice variability and trends, 1979-2006. Journal Of Geophysical Research-Oceans (2008) vol.
113 (C7) pp. C07003
- Perovich et al. Sunlight, water, and ice: Extreme Arctic sea ice melt during the summer of 2007. Geophysical Research Letters
(2008) vol. 35 (11) pp. L11501
- Zhang et al. What drove the dramatic retreat of Arctic sea ice during summer 2007?. Geophysical Research Letters (2008) vol.
35 (11) pp. L11505
- Kwok and Rothrock. Decline in Arctic sea ice thickness from submarine and ICESat records: 1958-2008. Geophysical Research
Letters (2009) vol. 36 pp. L15501
- Lawrence et al. Accelerated Arctic land warming and permafrost degradation during rapid sea ice loss. Geophysical Research
Letters (2008) vol. 35 (11) pp. L11506
- Francis et al. Winter Northern Hemisphere weather patterns remember summer Arctic sea-ice extent. Geophysical Research
Letters (2009) vol. 36 pp. L07503
- Bhatt et al. Circumpolar Arctic Tundra Vegetation Change Is Linked to Sea Ice Decline. Earth Interactions (2010) vol. 14
- Mastepanov et al. Large tundra methane burst during onset of freezing. Nature (2008) vol. 456 (7222) pp. 628-U58
- Dlugokencky et al. Observational constraints on recent increases in the atmospheric CH4 burden. Geophysical Research
Letters (2009) vol. 36 pp. L18803