Papers by Thomas Juul-Pedersen
So throw off the bowl ines, sai 1 away from the safe harbor. Catch the trade winds in your sails.... more So throw off the bowl ines, sai 1 away from the safe harbor. Catch the trade winds in your sails. Explore. Dream. Discover" (Mark Twain). What started a few years ago with a flight across the Atlantic Ocean soon became a voyage of exploration and learning. 1 will forever be indebted to my parents, Marian and Holger Juul-Pedersen, and my brother, Lars-Henrik Thorngreen, for al ways encouraging me to explore new horizons, while providing a profound sense of stability and unwavering support-always a safe harbor. A warrnhearted thanks to my new-found Canadian friends for making me feel so welcome. My Arctic journey started in Greenland where, during my second visit, 1 had the privilege ofworking with Dr. Christine Michel, as arranged by my Master of Science supervisor Dr. Torkel Gissel Nielsen. This meeting facilitated my involvement in a field project in Resolute Passage, Canadian Arctic, and led to a Ph.D. collaboration with Drs. Christine Michel and Michel Gosselin. 1 will always remain grateful to Christine and Michel for accepting me as their student. Christine and Michel contributed greatly to this thesis and 1 would like to acknowledge ail their guidance and hard work. Christine, thank you for always taking time to discuss the thesis and instilling a strong scientific professionalism. 1 really appreciate our friendship. Michel, 1 would like thank you for your always insightful and constructive input. 1 have enjoyed ail the good times we spent in the field, at meetings and during my stay in Rimouski.
Proceedings of the National Academy of Sciences
Global warming accelerates melting of glaciers and increases the supply of meltwater and associat... more Global warming accelerates melting of glaciers and increases the supply of meltwater and associated inorganic particles, nutrients, and organic matter to adjacent coastal seas, but the ecosystem impact is poorly resolved and quantified. When meltwater is delivered by glacial rivers, the potential impact could be a reduction in light and nutrient availability for primary producers while supplying allochthonous carbon for heterotrophic processes, thereby tipping the net community metabolism toward heterotrophy. To test this hypothesis, we determined physical and biogeochemical parameters along a 110-km fjord transect in NE Greenland fjord, impacted by glacial meltwater from the Greenland Ice Sheet. The meltwater is delivered from glacier-fed river outlets in the inner parts of the fjord, creating a gradient in salinity and turbidity. The planktonic primary production was low, 20–45 mg C m −2 d −1 , in the more turbid inner half of the fjord, increasing 10-fold to around 350 mg C m −2 ...
Journal of Geophysical Research: Oceans
Extreme seasonal changes in light conditions are among the key characteristics of high Arctic eco... more Extreme seasonal changes in light conditions are among the key characteristics of high Arctic ecosystems with far-reaching implications for their potential to generate biomass via photosynthetic primary production. As a result, Arctic ecosystems are usually characterized by a very short productive period during spring/summer that provides the entire annual biomass production available for higher trophic levels. Of particular ecological importance is the bottom ice algae bloom, which provides a pulse of primary production when no other significant food source exists in the marine ecosystem. Solar angle, sea ice cover and snow thickness are the main factors that determine timing and progression of the bottom ice algae bloom, while nutrient availability often affects the peak magnitude (and nutritional quality) of algal blooms. In this work, we summarize a pan-Arctic dataset of bottom ice algae biomass time series to describe latitudinal gradients in bloom development and the processes...
Goldschmidt2021 abstracts, 2021
Journal of Geophysical Research: Oceans, 2020
The accelerated melt of the Greenland Ice Sheet has been linked to a sudden increase in the prese... more The accelerated melt of the Greenland Ice Sheet has been linked to a sudden increase in the presence of warm subsurface coastal water in west Greenland. Yet pathways of warm coastal water along the entire west Greenland coast have remained largely unstudied. Here we present the first, near-synoptic hydrographic observations at both the continental slope and fjord entrances of the west Greenland coastal system from Cape Farewell (59°N) to Melville Bay (75°N) in summer 2016. We observed a distinct north-south division in the water mass distribution in west Greenland, approximately partitioned by the northern part of Davis Strait, and a division between the continental slope and fjord entrances. Waters from the regional southern freshwater source with origin in the East Greenland Current that rounds Cape Farewell are not observed to enter Baffin Bay. The regional heat source transported by the West Greenland Current is blocked by Southwest Greenland Coastal Water in the south but the deep connections in the north allow warm deep Subpolar Mode Water to enter fjords. Furthermore, we observed cold and relative saline Baffin Bay Polar Water over the inner part of the banks, periodically reaching as far south as 64°N, suggesting the presence of an undescribed southward current at the Southwest Greenland continental shelf.
Polar Biology, 2018
High-latitude fjord environments are undergoing dynamic seasonal changes, affecting spatio-tempor... more High-latitude fjord environments are undergoing dynamic seasonal changes, affecting spatio-temporal patterns in planktonic abundances. To investigate how physical gradients impact sub-Arctic planktonic protists (> 20 μm), a seasonal transect study was performed in 2013 during three periods of planktonic succession: spring, summer, and autumn. The samples were collected from the glacier-fjord-ocean transect in SW Greenland using two complementary sampling methods, i.e. net hauls (20-μm net) and Niskin bottles. The key drivers of the distribution of planktonic groups and dominant taxa were hydrographic properties (defined as 'time', salinity, and temperature) reflecting the area's seasonally changing circulation system. Cold and relatively saline waters in spring favoured the single haptophyte species Phaeocystis cf. pouchetii, while in summer, fresher waters influenced by glacial discharge favoured diatoms, followed by dinoflagellates and predatory ciliates in autumn. Our findings reveal a monodominant structure among the planktonic protists observed in each key sub-region and in each season. (1) Gedaniella boltonii (spring) was associated with inner fjord upwelling, (2) Chaetoceros sp. (summer) and Chaetoceros cf. socialis (autumn) were linked to 'glacial meltwater' circulation in the main fjord, and (3) Thalassiosira poroseriata (summer) and Skeletonema sp. (autumn) characterized warm and relatively saline offshore waters influenced by the West Greenland Current. The observed spatio-temporal patterns were linked to changes in hydrographic regimes driven by the interplay between the melting of the Greenland Ice Sheet and inflows of offshore, Atlantic-sourced waters.
Biogeosciences Discussions, 2014
The Greenland Ice Sheet releases large amounts of freshwater, which strongly influences the physi... more The Greenland Ice Sheet releases large amounts of freshwater, which strongly influences the physical and chemical properties of the adjacent fjord systems and continental shelves. Glacial meltwater input is predicted to increase strongly in the future, but the impact of meltwater on the carbonate dynamics of these productive coastal systems remains largely unquantified. Here we present seasonal observations of the carbonate system in the surface waters of a west Greenland tidewater outlet glacier fjord. Our data reveal a permanent undersaturation of CO<sub>2</sub> in the surface layer of the entire fjord and adjacent shelf. The average annual CO<sub>2</sub> uptake for the fjord is estimated to 65 g C m<sup>−2</sup> yr<sup>−1</sup> indicating that the fjord system is a strong sink for CO<sub>2</sub>. Primary production and the high input of glacial meltwater strongly affect the carbonate system in the Godthåbsfjord system. T...
Marine Chemistry, 2012
The present study is based on hourly samplings of wind speed, monthly sampling sessions of temper... more The present study is based on hourly samplings of wind speed, monthly sampling sessions of temperature, salinity, dissolved inorganic carbon, alkalinity, nutrients, primary productivity and vertical export in the outer sill region (station GF3) of a sub-arctic SW Greenland fjord (Godthåbsfjord) through 2005-2010. Air-sea CO 2 fluxes varied at GF3 from c. −20 g C m − 2 month − 1 (uptake from the atmosphere) to 25 g C m − 2 month − 1 (release to the atmosphere) during 2005-10. The average annual air-sea CO 2 flux of −83 to −108 g C m − 2 yr − 1 was within the range of the local gross annual primary productivity of 76-106 g C m − 2 yr − 1. Furthermore, the estimated vertical export of phytoplankton carbon to depths below 60 m of 38-89 g C m − 2 suggests that a large fraction of the mineralization (release of CO 2) occurs in deeper waters in the outer sill region of the fjord. However, there was no statistically significant correlation between average annual gross primary production and annual air-sea flux during 2005-2010, which suggests that regulation of pCO 2 in the fjord is more complex. Despite three confined periods with supersaturated pCO 2 conditions in surface waters during 2005-2010, Godthåbsfjord can be considered as a strong sink (7.2 tons C month − 1 km − 2) for atmospheric CO 2. In addition, measurements from Godthåbsfjord during the summer season showed that mixing between glacial meltwater and coastal water could explain a large part of the low pCO 2-values observed in the innermost part of the fjord. Finally, a larger survey confirmed the existence of very low pCO 2 conditions in nearshore and shelf waters around Southern Greenland.
Journal of Marine Systems, 2008
We examined the influence of the Mackenzie River plume on sinking fluxes of particulate organic a... more We examined the influence of the Mackenzie River plume on sinking fluxes of particulate organic and inorganic material on the Mackenzie Shelf, Canadian Arctic. Short-term particle interceptor traps were deployed under the halocline at 3 stations across the shelf during fall 2002 and at 3 stations along the shelf edge during summer 2004. During the two sampling periods, the horizontal patterns in sinking fluxes of particulate organic carbon (POC) and chlorophyll a (chl a) paralleled those in chl a biomass within the plume. Highest sinking fluxes of particulate organic material occurred at stations strongly influenced by the river plume (maximum POC sinking fluxes at 25 m of 98 mg C m − 2 d − 1 and 197 mg C m − 2 d − 1 in 2002 and 2004, respectively). The biogeochemical composition of the sinking material varied seasonally with phytoplankton and fecal pellets contributing considerably to the sinking flux in summer, while amorphous detritus dominated in the fall. Also, the sinking phytoplankton assemblage showed a seasonal succession from a dominance of diatoms in summer to flagellates and dinoflagellates in the fall. The presence of the freshwater diatom Eunotia sp. in the sinking assemblage directly underneath the river plume indicates the contribution of a phytoplankton community carried by the plume to the sinking export of organic material. Yet, increasing chl a and BioSi sinking fluxes with depth indicated an export of phytoplankton from the water column below the river plume during summer and fall. Grazing activity, mostly by copepods, and to a lesser extent by appendicularians, appeared to occur in a well-defined stratum underneath the river plume, particularly during summer. These results show that the Mackenzie River influences the magnitude and composition of the sinking material on the shelf in summer and fall, but does not constitute the only source of material sinking to depth at stations influenced by the river plume.
Cambridge Prisms: Coastal Futures
Fjord systems are transition zones between land and sea, resulting in complex and dynamic environ... more Fjord systems are transition zones between land and sea, resulting in complex and dynamic environments. They are of particular interest in the Arctic as they harbour ecosystems inhabited by a rich range of species and provide many societal benefits. The key drivers of change in European Arctic (i.e. Greenland, Svalbard, and Northern Norway) fjord socioecological systems are reviewed here, structured into five categories: cryosphere (sea-ice, glacier mass balance, glacial and riverine discharge), physics (seawater temperature, salinity, light), chemistry (carbonate system, nutrients), biology (primary production, biomass, species richness), and social (governance, tourism, fisheries). The data available for the past and present state of these drivers, as well as future model projections, are analysed in a companion paper. Changes to the two drivers at the base of most interactions within fjords, seawater temperature and glacier mass balance, will have the most significant and profound consequences on the future of European Arctic fjords. This is because even though governance may be effective at mitigating/adapting to local disruptions caused by the changing climate, there is possibly nothing that can be done to halt the melting of glaciers, the warming of fjord waters, and all of the downstream consequences that these two changes will have. This review provides the first transdisciplinary synthesis of the interactions between the drivers of change within Arctic fjord socio-ecological systems. Knowledge of what these drivers of change are, and how they interact with one another, should provide more expedient focus for future research on the needs of adapting to a changing Arctic.
Unprecedented melting of the Greenland Ice Sheet (GrIS) is impacting the coastal ocean, and its e... more Unprecedented melting of the Greenland Ice Sheet (GrIS) is impacting the coastal ocean, and its effects on fjord ecology remain understudied. It has been suggested that as glaciers retreat, primary production regimes may be altered, rendering fjords less productive. Here we present data from the paper Holding et al. (2019). Seasonal and spatial patterns of primary production in a high-latitude fjord affected by Greenland Ice Sheet run-off. <em>Biogeosciences</em>, <em>16</em>(19), 3777-3792, /doi.org/10.5194/bg-16-3777-2019. This paper investigates patterns of primary productivity in a northeast Greenland fjord (Young Sound, 74°N), which receives run-off from the GrIS via land-terminating glaciers. This dataset includes measures of size fractioned primary production and chlorophyll <em>a </em>biomass, as well as CTD data and biochemical parameters. Furthermore, primary production was measured using photosynthesis v. irradiance (PI) curves, thus PI...
Frontiers in Earth Science
Around the Greenlandic and Antarctic coastlines, sediment plumes associated with glaciers are sig... more Around the Greenlandic and Antarctic coastlines, sediment plumes associated with glaciers are significant sources of lithogenic material to the ocean. These plumes contain elevated concentrations of a range of trace metals, especially in particle bound phases, but it is not clear how these particles affect dissolved (<0.2 µm) metal distributions in the ocean. Here we show, using transects in 8 glacier fjords, trends in the distribution of dissolved iron, cobalt, nickel and copper (dFe, dCo, dNi, dCu). Following rapid dFe loss close to glacier outflows, dFe concentrations in particular showed strong similarities between different fjords. Similar dFe concentrations were also observed between seasons/years when Nuup Kangerlua (SW Greenland) was revisited in spring, mid- and late-summer. Dissolved Cu, dCo and dNi concentrations were more variable and showed different gradients with salinity depending on the fjord, season and year. The lack of consistent trends for dCu and dNi largely...
Journal of Geophysical Research: Biogeosciences
&lt;p&gt;The INTAROS project has a strong multidisciplinary focus, with tools for integra... more &lt;p&gt;The INTAROS project has a strong multidisciplinary focus, with tools for integration of data from atmosphere, ocean, cryosphere and terrestrial sciences, provided by institutions in Europe, North America and Asia. The dissemination activities aim to share knowledge about the Arctic with academia and with the general public.&lt;/p&gt; &lt;p&gt;The dissemination and exploitation activities are closely linked with communication and stakeholder engagement: the target audiences include research, public services, commercial operators, investment, insurance, environmental organizations, policy makers, local communities, and educational institutes. One of the INTAROS objectives is to disseminate project results to raise awareness of Arctic challenges and to inform and engage key users and stakeholder communities to improve their understanding of the Arctic environmental state and processes. The further aim is to build capacity in using the new products and services originating from the INTAROS project.&lt;/p&gt; &lt;p&gt;This contribution provides an overview of dissemination materials and products that are targeted towards teaching and/or intended for outreach purposes. The referenced teaching materials include products aimed at students ranging from school to university level, as well as the general public. The outreach materials are aimed at communicating knowledge about the INTAROS project, the scientific work, key findings as well as promoting general knowledge about climate and climate change.&lt;/p&gt; &lt;p&gt;&amp;#160;&lt;/p&gt;
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Papers by Thomas Juul-Pedersen