M. Oksman, A. B. Kvorning, C. Pearce, N. Korsgaard, J. M. Lea, M. Seidenkrantz, S. Ribeiro
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引用次数: 0
Abstract
Greenlandic fjords, located between the ice sheet and the ocean, are dynamic systems that can sustain highly variable levels of primary productivity and are sensitive to climate change. In our current climate trajectory, meltwater discharge is expected to significantly increase but its long‐term effects on fjord productivity are still poorly constrained. Paleo‐archives can offer valuable insights into long‐term effects. Here, we present two marine sediment core records from Nuup Kangerlua, Southwest Greenland. Our goal is to better understand to what extent, and on what time‐scales, climate fluctuations and associated glacier dynamic changes have impacted fjord productivity over the past ca. 3300 years. Our multiproxy records include diatom fluxes and assemblage composition, sediment biogeochemistry, and grain‐size distribution. Our study reveals that fjord productivity is tightly linked to regional climate variability; relatively higher productivity levels coincided with mild climate periods whereas the climate cooling of the last millennium led to a decrease in productivity. The diatom records suggest that lower productivity is associated with shorter or less intense summer blooms, increased sea‐ice cover and/or a stratified water column. Diatom assemblages demonstrate cold sea‐surface conditions around 1600 CE that might be linked to local advance of glaciers. Cold conditions and decreasing productivity culminated at 1850 CE, when glaciers in the fjord retreated and high glacial meltwater discharge would have altered the fjord hydrography, likely leading to limited nutrient availability. Our long‐term records support the idea that changing climate and cryosphere conditions have a non‐linear impact on the productivity of Greenlandic fjords.
期刊介绍:
Paleoceanography and Paleoclimatology (PALO) publishes papers dealing with records of past environments, biota and climate. Understanding of the Earth system as it was in the past requires the employment of a wide range of approaches including marine and lacustrine sedimentology and speleothems; ice sheet formation and flow; stable isotope, trace element, and organic geochemistry; paleontology and molecular paleontology; evolutionary processes; mineralization in organisms; understanding tree-ring formation; seismic stratigraphy; physical, chemical, and biological oceanography; geochemical, climate and earth system modeling, and many others. The scope of this journal is regional to global, rather than local, and includes studies of any geologic age (Precambrian to Quaternary, including modern analogs). Within this framework, papers on the following topics are to be included: chronology, stratigraphy (where relevant to correlation of paleoceanographic events), paleoreconstructions, paleoceanographic modeling, paleocirculation (deep, intermediate, and shallow), paleoclimatology (e.g., paleowinds and cryosphere history), global sediment and geochemical cycles, anoxia, sea level changes and effects, relations between biotic evolution and paleoceanography, biotic crises, paleobiology (e.g., ecology of “microfossils” used in paleoceanography), techniques and approaches in paleoceanographic inferences, and modern paleoceanographic analogs, and quantitative and integrative analysis of coupled ocean-atmosphere-biosphere processes. Paleoceanographic and Paleoclimate studies enable us to use the past in order to gain information on possible future climatic and biotic developments: the past is the key to the future, just as much and maybe more than the present is the key to the past.