Regional variability in the atmospheric nitrogen deposition signal and its transfer to the sediment record in Greenland lakes
Disruption of the nitrogen cycle is a major component of global environmental change. δ 15 N in lake sediments is increasingly used as a measure of reactive nitrogen input but problematically, the characteristic depleted δ 15 N signal is not recorded at all sites. We used a regionally replicated sam...
| Published in: | Limnology and Oceanography |
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| Main Authors: | , , , , , , |
| Format: | Article in Journal/Newspaper |
| Language: | English |
| Published: |
2018
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| Subjects: | |
| Online Access: | https://pure.au.dk/portal/da/publications/regional-variability-in-the-atmospheric-nitrogen-deposition-signal-and-its-transfer-to-the-sediment-record-in-greenland-lakes(29c4b7da-2aa4-41b6-b506-7cb5104ac99b).html https://doi.org/10.1002/lno.10936 http://www.scopus.com/inward/record.url?scp=85050496784&partnerID=8YFLogxK |
| Summary: | Disruption of the nitrogen cycle is a major component of global environmental change. δ 15 N in lake sediments is increasingly used as a measure of reactive nitrogen input but problematically, the characteristic depleted δ 15 N signal is not recorded at all sites. We used a regionally replicated sampling strategy along a precipitation and N-deposition gradient in SW Greenland to assess the factors determining the strength of δ 15 N signal in lake sediment cores. Analyses of snowpack N and δ 15 N-NO 3 and water chemistry were coupled with bulk sediment δ 15 N. Study sites cover a gradient of snowpack δ 15 N (ice sheet: −6‰; coast -10‰), atmospheric N deposition (ice sheet margin: ∼ 0.2 kg ha −1 yr −1 coast: 0.4 kg ha −1 yr −1 ) and limnology. Three 210 Pb-dated sediment cores from coastal lakes showed a decline in δ 15 N of ca. -1‰ from ∼ 1860, reflecting the strongly depleted δ 15 N of snowpack N, lower in-lake total N (TN) concentration (∼ 300 μg N L −1 ) and a higher TN-load. Coastal lakes have 3.7–7.1× more snowpack input of nitrate than inland sites, while for total deposition the values are 1.7–3.6× greater for lake and whole catchment deposition. At inland sites and lakes close to the ice-sheet margin, a lower atmospheric N deposition rate and larger in-lake TN pool resulted in greater reliance on N-fixation and recycling (mean sediment δ 15 N is 0.5–2.5‰ in most inland lakes; n = 6). The primary control of the transfer of the atmospheric δ 15 N deposition signal to lake sediments is the magnitude of external N inputs relative to the in-lake N-pool. |
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