Spatiotemporal variability in surface energy balance across tundra, snow and ice in Greenland

Lund, Magnus; Stiegler, Christian; Abermann, Jakob; Citterio, Michele; Hansen, Birger Ulf; As, Dirk van

doi:10.1007/s13280-016-0867-5

Cited by 31 publications

(27 citation statements)

References 42 publications

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“…We expect strong release of the heat, which was added to the lake within our study period, during late summer and autumn before refreeze (see Petrone & Rouse, ; Rouse et al, ), a period we did not cover with our measurements. High Res for the ice cover period (frozen: 34.1 W/m 2 ; melting: 201.0 W/m 2 ) confirmed that the energy required for ice cover melt represents an important EB component (Lund et al, ). The back‐calculation resulted in a slightly overestimated initial ice thickness but an ice decay rate during the melting ice cover period which is comparable to other studies (e.g., 1.5 cm/day for boreal lake, Jakkila et al, ; 6–10 cm/day for floating ice lakes, 11–16 cm/day for bedfast ice lakes in Northern Alaska, Arp et al, ).…”

Section: Discussionmentioning

confidence: 77%

Lake‐Atmosphere Heat Flux Dynamics of a Thermokarst Lake in Arctic Siberia

et al. 2018

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We conducted eddy covariance measurements from April to August 2014 on a Siberian thermokarst lake. The study site is located in the Lena River Delta and characterized as a floating ice lake. Heat fluxes differed in magnitudes, directions and temporal patterns depending on the lake surface conditions (“frozen” ice cover, ice cover melt, and open water). Significant heat release during frozen ice cover conditions highlighted the importance of lakes for the landscape heat budget and water balance. The energy balance was nearly closed during the open water period and highlighted the impact of melting energy on its closure during the ice cover period. Sensible and latent heat dynamics were driven by temperature and water vapor gradients scaled by wind speed, respectively. We calculated bulk aerodynamics transfer coefficients and evaluated the performance of the derived in situ and three independent heat flux parameterization schemes. We found that bulk transfer models perform moderately to poorly for the different lake surface conditions. During the open water period small‐scale temporal variability could not be represented by the models, particularly in case of latent heat flux. The model results were less sensitive to the specific model type than to the accuracy of the surface water temperature measurement, which is dependent on a well‐thought‐out measurement design. Our study stresses considerations that are crucial for similar campaigns in the future, in order to face the measurement challenges encountered on arctic lakes especially during the ice cover period.

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Section: Discussionmentioning

confidence: 77%

Lake‐Atmosphere Heat Flux Dynamics of a Thermokarst Lake in Arctic Siberia

et al. 2018

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“…Zackenberg station represents high-Arctic conditions in central north-east Greenland (74°28′N, 20°34′W, annual mean temperature −9°C between 1996−2015) and Disko Island represents low-Arctic conditions on an island in mid-south-west Greenland (69°15′N, 53°34′W, annual mean temperature −3.1°C between 1991−2015). Temperature measurements were obtained from climate measurement masts, methane fluxes from automatic chamber (AC) measurements and latent and sensible heat fluxes from eddy covariance measurements from Nuuk and Zackenberg (Pirk et al 2017, Lund et al 2017. AC measurements are only available since 2006 and 2008 from Zackenberg and Nuuk respectively.…”

Section: Temperature and Surface Flux Observationsmentioning

confidence: 99%

Potential future methane emission hot spots in Greenland

Geng

Christensen

2019

Environ. Res. Lett.

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Climate models have been making significant progress encompassing an increasing number of complex feedback mechanisms from natural ecosystems. Permafrost thaw and subsequent induced greenhouse gas emissions, however, remain a challenge for climate models at large. Deducing permafrost conditions and associated greenhouse gas emissions from parameters that are simulated in climate models would be a helpful step towards estimating emission budgets from permafrost regions. Here we use a regional climate model with a 5 km horizontal resolution to assess future potential methane (CH 4 ) emissions over presently unglaciated areas in Greenland under an RCP8.5 scenario. A simple frost index is applied to estimate permafrost conditions from the model output. CH 4 flux measurements from two stations in Greenland; Nuuk representing sub-Arctic and Zackenberg high-Arctic climate, are used to establish a relationship between emissions and near surface air temperature. Permafrost conditions in Greenland change drastically by the end of the 21st century in an RCP8.5 climate. Continuous permafrost remains stable only in North Greenland, the north-west coast, the northern tip of Disko Island, and Nuussuaq. Southern Greenland conditions only sustain sporadic permafrost conditions and largely at high elevations, whereas former permafrost in other regions thaws. The increasing thawed soil leads to increasing CH 4 emissions. Especially the area surrounding Kangerlussuaq, Scoresby Land, and the southern coast of Greenland exhibit potentially high emissions during the longer growing season. The constructed maps and budgets combining modelled permafrost conditions with observed CH 4 fluxes from CH 4 promoting sites represent a useful tool to identify areas in need of additional monitoring as they highlight potential CH 4 hot spots.

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“…The study site is located within a Cassiope tetragona tundra heath, dominated by C. tetragona, Dryas integrifolia and Vaccinium uliginosum, with patches of mosses. Several studies on soil and permafrost (Palmtag et al, 2015;Westermann et al, 2015), surface energy balance (Lund et al, 2014;Stiegler et al, 2016;Lund et al, 2017) and carbon exchange (Mastepanov et al, 2008;Lund et al, 2012;Elberling et al, 2013) have been published based on data from this site. A rich dataset is available from this site through the extensive, cross-disciplinary Greenland Ecosystem Monitoring programme (www.g-e-m.dk).…”

Section: Zackenbergmentioning

confidence: 99%

Carbon stocks and fluxes in the high latitudes: using site-level data to evaluate Earth system models

et al. 2017

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Abstract. It is important that climate models can accurately simulate the terrestrial carbon cycle in the Arctic due to the large and potentially labile carbon stocks found in permafrost-affected environments, which can lead to a positive climate feedback, along with the possibility of future carbon sinks from northward expansion of vegetation under climate warming. Here we evaluate the simulation of tundra carbon stocks and fluxes in three land surface schemes that each form part of major Earth system models (JSBACH, Germany; JULES, UK; ORCHIDEE, France). We use a site-level approach in which comprehensive, high-frequency datasets allow us to disentangle the importance of different processes. The models have improved physical permafrost processes and there is a reasonable correspondence between the simulated and measured physical variables, including soil temperature, soil moisture and snow.We show that if the models simulate the correct leaf area index (LAI), the standard C3 photosynthesis schemes produce the correct order of magnitude of carbon fluxes. Therefore, simulating the correct LAI is one of the first priorities. LAI depends quite strongly on climatic variables alone, as we see by the fact that the dynamic vegetation model can simulate most of the differences in LAI between sites, based almost entirely on climate inputs. However, we also identify an influence from nutrient limitation as the LAI becomes too large at some of the more nutrient-limited sites. We conclude that including moss as well as vascular plants is of primary importance to the carbon budget, as moss contributes a large fraction to the seasonal CO 2 flux in nutrient-limited conditions. Moss photosynthetic activity can be strongly influenced by the moisture content of moss, and the carbon uptake can be significantly different from vascular plants with a similar LAI.The soil carbon stocks depend strongly on the rate of input of carbon from the vegetation to the soil, and our analysis suggests that an improved simulation of photosynthesis would also lead to an improved simulation of soil carbon stocks. However, the stocks are also influenced by soil carbon burial (e.g. through cryoturbation) and the rate of heterotrophic respiration, which depends on the soil physical state. More detailed below-ground measurements are needed to fully evaluate biological and physical soil processes. Furthermore, even if these processes are well modelled, the soil carbon profiles cannot resemble peat layers as peat accumulation processes are not represented in the models.Thus, we identify three priority areas for model development: (1) dynamic vegetation including (a) climate and (b) nutrient limitation effects; (2) adding moss as a plant functional type; and an (3) improved vertical profile of soil carbon including peat processes.

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Spatiotemporal variability in surface energy balance across tundra, snow and ice in Greenland

Cited by 31 publications

References 42 publications

Lake‐Atmosphere Heat Flux Dynamics of a Thermokarst Lake in Arctic Siberia

Lake‐Atmosphere Heat Flux Dynamics of a Thermokarst Lake in Arctic Siberia

Potential future methane emission hot spots in Greenland

Carbon stocks and fluxes in the high latitudes: using site-level data to evaluate Earth system models

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