DOI: 10.5194/tc-15-2083-2021
论文题名: Early spring subglacial discharge plumes fuel under-ice primary production at a Svalbard tidewater glacier
作者: Reiner Vonnahme T. ; Persson E. ; Dietrich U. ; Hejdukova E. ; Dybwad C. ; Elster J. ; Chierici M. ; Gradinger R.
刊名: Cryosphere
ISSN: 19940416
出版年: 2021
卷: 15, 期: 4 起始页码: 2083
结束页码: 2107
语种: 英语
英文关键词: Antarctic Bottom Water
; biomass
; bottom water
; phytoplankton
; primary production
; sea ice
; spring (hydrology)
; subglacial environment
; tidewater glacier
; Arctic
; Billefjorden
; Spitsbergen
; Svalbard
; Svalbard
; Svalbard and Jan Mayen
英文摘要: Subglacial upwelling of nutrient-rich bottom water is known to sustain elevated summer primary production in tidewater-glacier-influenced fjord systems. However, the importance of subglacial upwelling during the early spring season has not been considered yet. We hypothesized that subglacial discharge under sea ice is present in early spring and that its flux is sufficient to increase phytoplankton primary productivity. We evaluated the effects of the submarine discharge on primary production in a seasonally fast-ice covered Svalbard fjord (Billefjorden) influenced by a tidewater outlet glacier in April and May 2019. We found clear evidence for subglacial discharge and upwelling. Although the estimated bottom-water entrainment factor (1.6) and total fluxes were lower than in summer studies, we still observed substantial impact on the fjord ecosystem and primary production at this time of the year. The subglacial discharge leads to a salinity-stratified surface water layer and sea ice formation with low bulk salinity and permeability. The combination of the stratified surface layer, a 2-fold higher under-ice irradiance due to thinner snow cover, and higher N and Si concentrations at the glacier front supported phytoplankton primary production 2 orders of magnitude higher (42.6 mg C m-2 d-1) compared to a marine reference site at the fast-ice edge. Reciprocal transplant experiments showed that nutrient supply increased phytoplankton primary production by approximately 30 %. The brackish-water sea ice at the glacier front with its low bulk salinity contained a reduced brine volume, limiting the inhabitable brine channel space and nutrient exchange with the underlying seawater compared to full marine sea ice. Microbial and algal communities were substantially different in subglacial-influenced water and sea ice compared to the marine reference site, sharing taxa with the subglacial outflow water. We suggest that with climate change, the retreat of tidewater glaciers in early spring could lead to decreased under-ice phytoplankton primary production. In contrast, sea ice algae production and biomass may become increasingly important, unless sea ice disappears first, in which case spring phytoplankton primary production may increase. © 2021 EDP Sciences. All rights reserved. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/164788
Appears in Collections: 气候变化与战略
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作者单位: Department of Arctic and Marine Biology, UiT the Arctic University of Norway, Tromsø, Norway; Department of Ecology, Faculty of Science, Charles University, Prague, Czech Republic; Centre for Polar Ecology, University of South Bohemia, České Budějovice, Czech Republic; Institute of Botany Ascr, Třeboň, Czech Republic; Institute of Marine Research, Tromsø, Norway; University Centre in Svalbard (UNIS), Longyearbyen, Svalbard and Jan Mayen
Recommended Citation:
Reiner Vonnahme T.,Persson E.,Dietrich U.,et al. Early spring subglacial discharge plumes fuel under-ice primary production at a Svalbard tidewater glacier[J]. Cryosphere,2021-01-01,15(4)