 |
| Titel |
Greenland Ice Sheet exports labile organic carbon to the Arctic oceans |
| VerfasserIn |
E. C. Lawson, J. L. Wadham, M. Tranter, M. Stibal, G. P. Lis, C. E. H. Butler, J. Laybourn-Parry, P. Nienow, D. Chandler, P. Dewsbury |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1726-4170
|
| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 11, no. 14 ; Nr. 11, no. 14 (2014-07-31), S.4015-4028 |
| Datensatznummer |
250117531
|
| Publikation (Nr.) |
 copernicus.org/bg-11-4015-2014.pdf |
|
|
|
|
|
| Zusammenfassung |
| Runoff from small glacier systems contains dissolved organic carbon (DOC)
rich in protein-like, low molecular weight (LMW) compounds, designating
glaciers as an important source of bioavailable carbon for downstream
heterotrophic activity. Fluxes of DOC and particulate organic carbon (POC)
exported from large Greenland catchments, however, remain unquantified,
despite the Greenland Ice Sheet (GrIS) being the largest source of global
glacial runoff (ca. 400 km3 yr−1). We report high and episodic
fluxes of POC and DOC from a large (>600 km2) GrIS
catchment during contrasting melt seasons. POC dominates organic carbon (OC)
export (70–89% on average), is sourced from the ice sheet bed, and
contains a significant bioreactive component (9% carbohydrates). A major
source of the "bioavailable" (free carbohydrate) LMW–DOC fraction is
microbial activity on the ice sheet surface, with some further addition of
LMW–DOC to meltwaters by biogeochemical processes at the ice sheet bed. The
bioavailability of the exported DOC (26–53%) to downstream marine
microorganisms is similar to that reported from other glacial watersheds.
Annual fluxes of DOC and free carbohydrates during two melt seasons were
similar, despite the approximately two-fold difference in runoff fluxes,
suggesting production-limited DOC sources. POC fluxes were also insensitive
to an increase in seasonal runoff volumes, indicating a supply limitation in
suspended sediment in runoff. Scaled to the GrIS, the combined DOC
(0.13–0.17 Tg C yr−1 (±13%)) and POC fluxes (mean =
0.36–1.52 Tg C yr−1 (±14%)) are of a similar order of
magnitude to a large Arctic river system, and hence may represent an
important OC source to the near-coastal North Atlantic, Greenland and
Labrador seas. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|