GreenBlue – A green-blue link made browner: how terrestrial climate change affects marine ecology (completed)

• Berezovski, Aleksandr; Hessen, Dag Olav; Børseth, Hanne Halkjelsvik & Andersen, Tom (2025). Optical properties of dissolved organic matter along a salinity gradient from a boreal river estuary to open coastal waters. Marine and Freshwater Research. ISSN 1323-1650. 76(11). doi: 10.1071/mf24244. Full text in Research Archive Show summary

  Context Water darkening is an increasingly relevant problem affecting many coastal ecosystems, and it is exacerbated by human activity and climate change. Aims To determine the spectral, isotopic, and quantitative changes in coloured dissolved organic matter (CDOM) across a salinity gradient from the Glomma River to the outer Oslofjord. Methods CDOM absorbance was measured on a spectrophotometer and organic carbon in the water column was analysed using stable isotopes. Key results Spectral slope and CDOM absorption at 443 nm decreases linearly with an increasing salinity. CDOM absorption exhibited significant variations, with low-salinity samples showing higher light absorption per unit of carbon, but little seasonal variations. δ13C of TOC analysis showed a strong positive correlation with salinity. Conclusion Dissolved organic matter optical characteristics of coastal waters are tightly linked to CDOM. The distance to the river mouth and to the shore are some of the most important factors affecting water clarity. The δ13C of TOC analysis indicated a linear transition from terrestrial to marine carbon sources. Implications The study has shown how coastal darkening can be an important ecological issue mainly in near-coastal areas and describes valuable diagnostic tools for tracking it.

• Berezovski, Aleksandr; Hessen, Dag Olav & Andersen, Tom (2025). Photon budgets and the relative effects of CDOM and pigment absorptions on primary production along a coastal salinity gradient. Frontiers in Photobiology. 2. doi: 10.3389/fphbi.2024.1452747. Full text in Research Archive Show summary

  The study highlights the critical role of CDOM in coastal light attenuation and its impact on primary production (PP). We investigated the spectral attenuation of light due to water, phytoplankton pigments, detritus and coloured dissolved organic matter (CDOM) along a salinity gradient in the outer Oslofjord, Norway. By examining the effects of these components across different seasons, we aimed to elucidate their relative contributions to light absorption and PP. The findings suggest that increased terrestrial CDOM inputs, driven by climate, changed atmospheric deposition and land-use changes, could significantly affect coastal ecosystems by altering light attenuation and consequently PP and potentially leading to other ecological pressures. CDOM consistently dominated light absorption across all stations and seasons, contributing 50%–80% of the total absorption of photosynthetically active radiation. The absorption by CDOM and detritus decreased with increasing salinity, while phytoplankton absorption followed a seasonal succession. PP estimates show high seasonal variability from maximums in June to minimums in November, mainly attributed to, changes in seasonal light availability and phytoplankton biomass, followed by light attenuation by CDOM and differences in quantum yields of photosystem II (PSII). Nutrient analysis showed a seasonal pattern, with the highest nitrogen concentrations in November and depletion during more productive seasons, as well as conservative mixing throughout the salinity gradient. CDOM absorption played substantial, albeit not leading, role in influencing PP estimates, derived from a bio-optical model. CDOM was the main determinant of light attenuation across most wavelegnths.

• Jessen, Henrik Høiberg; Opdal, Anders Martin Frugård & Enberg, Katja (2025). Increasing temperatures counteract the evolutionary consequences of fishing in model of Northeast Arctic Cod (Gadus morhua). Scientific Reports. 15(1). doi: 10.1038/s41598-025-15394-x. Full text in Research Archive Show summary

  Fisheries and climate warming are two stressors known to induce evolutionary changes in fish life histories. While their independent effects have been well documented, their interactive effects are less charted, although likely important for sustainable fisheries management and conservation strategies. We investigated the evolutionary responses of the Northeast Arctic cod stock ( Gadus morhua ) to warming temperatures and fishing pressure using a mechanistic modeling approach. Our individual-based simulation model incorporates explicit energy and oxygen budgets, and a simplified genetics framework to capture the complex interactions among traits governing energy acquisition/allocation and maturation schedules. Our results provide a theoretical basis for positive consequences for this particular cod stock in a warming climate. Warmer temperatures increased the aerobic scope, which reduced natural mortality. We found that if food availability and temperature are not linked, a warming climate leads to larger population sizes. By selecting for maturation at larger sizes, adaptation to warming climate at least partially counteracts the evolutionary consequences of fishing, namely smaller body sizes and earlier maturation. Our findings emphasize the benefits of adaptive management approaches, considering fish as evolving organisms and integrating ocean warming into fisheries management strategies.

• Sandven, Håkon Johan; Granskog, Mats; Opdal, Anders Martin Frugård; Connan-McGinty, Stacey; Hamre, Børge & Mckee, David James Christopher (2025). Increased Light Availability in the Northern Barents Sea Driven by Sea Ice Loss. Journal of Geophysical Research (JGR): Oceans. ISSN 2169-9275. 130(6). doi: 10.1029/2025JC022370. Full text in Research Archive Show summary

  The Barents Sea region is a hotspot for global climate change, with larger-than-average temperature increase and sea ice loss. This has led to massive changes in the underwater light environment, which is a key environmental driver for polar marine ecosystems given the extreme seasonal variability. The ecosystem consequences of a changing underwater lightscape remains poorly characterized. Here, we model the changes in availability of photosynthetically available radiation Epar in the Barents Sea from 1979 to 2022, using the underwater irradiance model HEIMDALL, which is developed and validated for use in the Barents Sea and has recently been expanded for use in ice-covered or ice-influenced waters. Our results show that the potential growth season for phytoplankton has become more than 1 month longer in large parts of the northern Barents Sea. The largest changes have been in the northeastern part of the region with up to 60 days. The primary environmental driver for light availability is the sea ice concentration (SIC), particularly in spring, with a Kendall rank correlation coefficient t = −0.69. Cloud cover and phytoplankton are important second-order factors (t = −0.4 after controlling for SIC), whereas snow and ice thickness have a negligible effect after controlling for SIC due to strong interdependencies. We observe a partially stepwise change in the 2000s, but sea ice driven interannual variability has been large throughout the period. Sea ice and snow have a limited impact on the spectral quality of light, omitting any impurities or sea ice algae.

• Opdal, Anders Martin Frugård; Wright, Peter J.; Blom, Geir; Höffle, Hannes; Lindemann, Christian & Kjesbu, Olav Sigurd (2024). Spawning fish maintains trophic synchrony across time and space beyond thermal drivers. Ecology. ISSN 0012-9658. 105(6). doi: 10.1002/ecy.4304. Full text in Research Archive Show summary

  Increasing ocean temperature will speed up physiological rates of ectotherms. In fish, this is suggested to cause earlier spawning due to faster oocyte growth rates. Over time, this could cause spawning time to become decoupled from the timing of offspring food resources, a phenomenon referred to as trophic asynchrony. We used biological data, including body length, age, and gonad developmental stages collected from >125,000 individual Northeast Arctic cod (Gadus morhua) sampled between 59 and 73° N in 1980–2019. Combined with experimental data on oocyte growth rates, our analyses show that cod spawned progressively earlier by about a week per decade, partly due to ocean warming. It also appears that spawning time varied by more than 40 days, depending on year and spawning location. The significant plasticity in spawning time seems to be fine-tuned to the local phytoplankton spring bloom phenology. This ability to partly overcome thermal drivers and thus modulate spawning time could allow individuals to maximize fitness by closely tracking local environmental conditions important for offspring survival. Our finding highlights a new dimension for trophic match–mismatch and should be an important consideration in models used to predict phenology dynamics in a warmer climate.

• Aas, Elin Cecilie Ristorp; Althuizen, Inge; Tang, Hui; Geange, Sonya Rita; Lieungh, Eva & Vandvik, Vigdis [Show all 7 contributors for this article] (2024). Implications of climate and litter quality for simulations of litterbag decomposition at high latitudes. Biogeosciences. ISSN 1726-4170. 21(16), p. 3789–3817. doi: 10.5194/bg-21-3789-2024. Full text in Research Archive Show summary

  Litter decomposition is a vital part of the carbon cycle and is thoroughly studied both in the field and with models. Although temporally and spatially limited, litterbag decomposition experiments are often used to calibrate and evaluate soil models, coupled to land models, that are intended for use on large scales. We used the microbially explicit soil decomposition model MIMICS+ to replicate two high-latitude litterbag decomposition experiments of different spatial and temporal scales. We investigated how well the model represented observed mass loss in terms of the controlling factors of climate and litter quality and their relative importance with time. In addition to default model forcing, we used measured and site-specific model-derived microclimatic variables (soil moisture and temperature), hypothesizing that this would improve model results. We found that MIMICS+ represented mass loss after 1, 3, and 6 years well across a climatic gradient of Canadian sites but had more variable results for 1-year mass loss across a climate grid in southern Norway. In terms of litter quality, the litter metabolic fraction had more influence on modeled mass loss than the carbon-to-nitrogen ratio of the litter. Using alternative microclimate sources led to up to 23 % more mass remaining and down to 22 % less mass remaining compared to the simulations using default model inputs. None of the input alternatives significantly improved results compared to using the default model setup. We discuss possible causes for our findings and suggest measures to better utilize short-term field experiments to inform microbially explicit decomposition models.

• Opdal, Anders Martin Frugård; Lindemann, Christian; Andersen, Tom; Hessen, Dag Olav; Fiksen, Øyvind & Aksnes, Dag Lorents (2024). Land use change and coastal water darkening drive synchronous dynamics in phytoplankton and fish phenology on centennial timescales. Global Change Biology. ISSN 1354-1013. 30(5). doi: 10.1111/gcb.17308. Full text in Research Archive Show summary

  At high latitudes, the suitable window for timing reproductive events is particularly narrow, promoting tight synchrony between trophic levels. Climate change may disrupt this synchrony due to diverging responses to temperature between, for example, the early life stages of higher trophic levels and their food resources. Evidence for this is equivocal, and the role of compensatory mechanisms is poorly understood. Here, we show how a combination of ocean warming and coastal water darkening drive long-term changes in phytoplankton spring bloom timing in Lofoten Norway, and how spawning time of Northeast Arctic cod responds in synchrony. Spring bloom timing was derived from hydrographical observations dating back to 1936, while cod spawning time was estimated from weekly fisheries catch and roe landing data since 1877. Our results suggest that land use change and freshwater run-off causing coastal water darkening has gradually delayed the spring bloom up to the late 1980s after which ocean warming has caused it to advance. The cod appear to track phytoplankton dynamics by timing gonadal development and spawning to maximize overlap between offspring hatch date and predicted resource availability. This finding emphasises the importance of land–ocean coupling for coastal ecosystem functioning, and the potential for fish to adapt through phenotypic plasticity.

• Aas, Elin Cecilie Ristorp; Wit, Heleen de & Berntsen, Terje Koren (2024). Modeling boreal forest soil dynamics with the microbially explicit soil model MIMICS+ (v1.0). Geoscientific Model Development. ISSN 1991-959X. 17(7), p. 2929–2959. doi: 10.5194/gmd-17-2929-2024. Full text in Research Archive Show summary

  Understanding carbon exchange processes between land reservoirs and the atmosphere is essential for predicting carbon–climate feedbacks. Still, considerable uncertainty remains in the representation of the terrestrial carbon cycle in Earth system models. An emerging strategy to constrain these uncertainties is to include the role of different microbial groups explicitly. Following this approach, we extend the framework of the MIcrobial-MIneral Carbon Stabilization (MIMICS) model with additional mycorrhizal groups and a nitrogen cycle that includes a novel representation of inorganic nitrogen sorption to particles via a Langmuir isotherm. MIMICS+ v1.0 is designed to capture and quantify relationships between soil microorganisms and their environment, with a particular emphasis on boreal ecosystems. We evaluated MIMICS+ against podzolic soil profiles in Norwegian forests as well as the conventional Community Land Model (CLM). MIMICS+ matched observed carbon stocks better than CLM and gave a broader range of C:N

• Crapart, Camille Marie; Finstad, Anders Gravbrøt; Hessen, Dag Olav; Vogt, Rolf David & Andersen, Tom (2023). Spatial predictors and temporal forecast of total organic carbon levels in boreal lakes. Science of the Total Environment. ISSN 0048-9697. 870. doi: 10.1016/j.scitotenv.2023.161676. Full text in Research Archive Show summary

  Browning of Fennoscandian boreal lakes is raising concerns for negative ecosystem impacts as well as reduced drinking water quality. Declined sulfur deposition and warmer climate, along with afforestation, other climate impacts and less outfield grazing, have resulted in increased fluxes of Total Organic Carbon (TOC) from catchments to freshwater, and subsequently to coastal waters. This study assesses the major governing factors for increased TOC levels among several catchment characteristics in almost 5000 Fennoscandian lakes and catchments. Normalized Difference Vegetation Index (NDVI), a proxy for plant biomass, and the proportions of peatland in the catchment, along with surface runoff intensity and nitrogen deposition loading, were identified as the main spatial predictors for lake TOC concentrations. A multiple linear model, based on these explanatory variables, was used to simulate future TOC concentration in surface runoff from coastal drainage basins in 2050 and 2100, using the forecasts of climatic variables in two of the Shared Socio-economic Pathways (SSP): 1-2.6 (+2 °C) and 3-7.0 (+4,5 °C). These scenarios yield contrasting effects. SSP 1-2.6 predicts an overall decrease of TOC export to coastal waters, while SSP 3-7.0 in contrast leads to an increase in TOC export.

• Jessen, Henrik Høiberg; Opdal, Anders Martin Frugård & Enberg, Katja Susanna (2023). Life-history evolution in response to foraging risk, modelled for Northeast Arctic cod (Gadus morhua). Ecological Modelling. ISSN 0304-3800. 482. doi: 10.1016/j.ecolmodel.2023.110378. Full text in Research Archive Show summary

  Foraging behaviour is known to be a key element in ecology and evolution. Increased foraging intensity increases energy intake, which is useful for growth and reproduction but comes at the cost of higher mortality risk due to increased exposure to predators. Here, we investigate these trade-offs through an individual-based, mechanistic modelling framework adapted to the Northeast Arctic Cod. The model incorporates a series of life-history traits, survival trade-offs, and heritability, which allow evolution to occur and optimal strategies to emerge due to individual trait combinations and their fitness consequences. By altering the relationship between foraging intensity and mortality risk, we find that increased risk causes evolution towards lower foraging effort leading to lower growth and in turn, earlier maturation and a faster pace of life. These results build on previous studies by demonstrating behavioural evolution without direct anthropogenic stressors. Natural mortality among fish is poorly understood, and these results highlight an interesting point of further research that could help future modelling approaches make more accurate assumptions about natural mortality and its components.

• Opdal, Anders Martin Frugård; Andersen, Tom; Hessen, Dag Olav; Lindemann, Christian & Aksnes, Dag Lorents (2023). Tracking freshwater browning and coastal water darkening from boreal forests to the Arctic Ocean. Limnology and Oceanography Letters. 8(4), p. 611–619. doi: 10.1002/lol2.10320. Full text in Research Archive Show summary

  The forest cover of Northern Europe has been steadily expanding during the last 120 years. More terrestrial vegetation and carbon fixation leads to more export to surface waters. This may cause freshwater browning, as more degraded plant-litter ends up as chromophoric (colored) dissolved organic matter. Although most freshwater ultimately drains to coastal waters, the link between freshwater browning and coastal water darkening is poorly understood. Here, we explore this relationship through a combination of centennial records of forest cover and coastal water clarity, contemporary optical measurements in lakes and coastal waters, as well as an ocean drift model. We suggest a link between forest cover in Northern Europe and coastal water clarity in the Baltic, Kattegat, and Skagerrak Sea and show how brown-colored freshwater from Northern European catchments can dictate coastal water clarity across thousands of kilometers, from the Baltic lakes to the Barents Sea.

• Kaartvedt, Stein; Røstad, Anders; Opdal, Anders Frugård & Aksnes, Dag Lorents (2019). Herding mesopelagic fish by light. Marine Ecology Progress Series. ISSN 0171-8630. 625, p. 225–231. doi: 10.3354/meps13079. Full text in Research Archive Show summary

  To assess organisms forming mesopelagic scattering layers in the Red Sea, we took advantage of their reactions to light. We used a remotely operated vehicle (ROV) equipped with LED lamps for herding the acoustic targets down to the bottom (700 m), while concurrently monitoring the event by shipborne and deployed echosounders as well as video footage from the ROV. In essence, entire mesopelagic scattering layers at 38 kHz were moved downwards until the organisms became trapped and concentrated at the bottom and identified as fish from video images. However, responses to the artificial light source appeared to include both repulsion and attraction. An individual-based model reproduced the herding event by assuming a dichotomous response to light where targets close to the light source are attracted, while targets further away are repulsed. We hypothesize that attraction is associated with the artificial light acting as a point source (beam light), while the repulsion is associated with the artificial light acting as diffuse light.

• Opdal, Anders Frugård; Lindemann, Christian & Aksnes, Dag Lorents (2019). Centennial decline in North Sea water clarity causes strong delay in phytoplankton bloom timing. Global Change Biology. ISSN 1354-1013. 25(11), p. 3946–3953. doi: 10.1111/gcb.14810. Full text in Research Archive Show summary

  With climate warming, a widespread expectation is that events in spring, such as flowering, bird migrations, and insect bursts, will occur earlier because of increasing temperature. At high latitudes, increased ocean temperature is suggested to advance the spring phytoplankton bloom due to earlier stabilization of the water column. However, climate warming is also expected to cause browning in lakes and rivers due to increases in terrestrial greening, ultimately reducing water clarity in coastal areas where freshwater drain. In shallow areas, decreased retention of sediments on the seabed will add to this effect. Both browning and resuspension of sediments imply a reduction of the euphotic zone and Sverdrup's critical depth leading to a delay in the spring bloom, counteracting the effect of increasing temperature. Here, we provide evidence that such a transparency reduction has already taken place in both the deep and shallow areas of the North Sea during the 20th century. A sensitivity analysis using a water column model suggests that the reduced transparency might have caused up to 3 weeks delay in the spring bloom over the last century. This delay stands in contrast to the earlier bloom onset expected from global warming, thus highlighting the importance of including changing water transparency in analyses of phytoplankton phenology and primary production. This appears to be of particular relevance for coastal waters, where increased concentrations of absorbing and scattering substances (sediments, dissolved organic matter) have been suggested to lead to coastal darkening.

• Opdal, Anders Frugård; Brodeur, Richard D.; Cieciel, Kristin; Daskalov, Georgi; Mihneva, Vesselina & Ruzicka, James J [Show all 8 contributors for this article] (2019). Unclear associations between small pelagic fish and jellyfish in several major marine ecosystems. Scientific Reports. 9(1), p. 1–12. doi: 10.1038/s41598-019-39351-7. Full text in Research Archive Show summary

  During the last 20 years, a series of studies has suggested trends of increasing jellyfish (Cnidaria and Ctenophora) biomass in several major ecosystems worldwide. Some of these systems have been heavily fished, causing a decline among their historically dominant small pelagic fish stocks, or have experienced environmental shifts favouring jellyfish proliferation. Apparent reduction in fish abundance alongside increasing jellyfish abundance has led to hypotheses suggesting that jellyfish in these areas could be replacing small planktivorous fish through resource competition and/or through predation on early life stages of fish. In this study, we test these hypotheses using extended and published data of jellyfish, small pelagic fish and crustacean zooplankton biomass from four major ecosystems within the period of 1960 to 2014: the Southeastern Bering Sea, the Black Sea, the Northern California Current and the Northern Benguela. Except for a negative association between jellyfish and crustacean zooplankton in the Black Sea, we found no evidence of jellyfish biomass being related to the biomass of small pelagic fish nor to a common crustacean zooplankton resource. Calculations of the energy requirements of small pelagic fish and jellyfish stocks in the most recent years suggest that fish predation on crustacean zooplankton is 2–30 times higher than jellyfish predation, depending on ecosystem. However, compared with available historical data in the Southeastern Bering Sea and the Black Sea, it is evident that jellyfish have increased their share of the common resource, and that jellyfish can account for up to 30% of the combined fish-jellyfish energy consumption. We conclude that the best available time-series data do not suggest that jellyfish are outcompeting, or have replaced, small pelagic fish on a regional scale in any of the four investigated ecosystems. However, further clarification of the role of jellyfish requires higher-resolution spatial, temporal and taxonomic sampling of the pelagic community.

• Aarflot, Johanna Myrseth; Aksnes, Dag Lorents; Opdal, Anders Frugård; Skjoldal, Hein Rune & Fiksen, Øyvind (2018). Caught in broad daylight: Topographic constraints of zooplankton depth distributions. Limnology and Oceanography. ISSN 0024-3590. 64(3), p. 849–859. doi: 10.1002/lno.11079. Full text in Research Archive Show summary

  For visual predators, sufficient light is critical for prey detection and capture. Because light decays exponentially with depth in aquatic systems, vertical movement has become a widespread strategy among zooplankton for avoiding visual predation. However, topographical features such as seamounts have been shown to block their descent, trapping them in illuminated waters with potential feeding benefits for visually searching fish. Here, we present an extensive and previously unpublished dataset on the vertical distribution of zooplankton in the topographically rugged Barents Sea, a continental shelf region hosting some of the largest fish stocks in the world. By modeling the ambient light exposure of zooplankton in relation to the bathymetry, we find support for a similar blockage mechanism. During daytime, zooplankton are exposed to four orders of magnitude more light above shallow banks than in the deeper water surrounding the banks. We show that zooplankton depth distributions are highly related to zooplankton size and that the bottom constrains the vertical distributions. Consequently, zooplankton remain in the planktivores’ visual feeding habitat over the banks but not in deeper areas. Bottom topography and light absorbance are significant determinants of the seascape ecology across continental shelves with heterogeneous bathymetry.

View all works in NVA

• Opdal, Anders Martin Frugård (2026). Havet langs kysten har blitt mørkere. Det er darlig nytt for fisk, sjøgress og tare. [Journal]. Bergens Tidende. Full text in Research Archive Show summary

  Fra 2003 til 2022 ble verdens hav mørkere ned til 200 meters dyp.

• Opdal, Anders Martin Frugård (2026). Havet langs kysten har blitt mørkere. Det er darlig nytt for fisk, sjøgress og tare. [Journal]. Aftenposten. Full text in Research Archive Show summary

  Fra 2003 til 2022 ble verdens hav mørkere ned til 200 meters dyp.

• Opdal, Anders Martin Frugård (2026). Regional dynamics of dissolved organic matter from the Bothnian Bay to the Barents Sea. Full text in Research Archive
• Fiksen, Øyvind (2026). Novel fish ranching with natural plankton feed attracted by artificial light. doi: https:/agu.confex.com/agu/osm26/meetingapp.cgi/Paper/2040082. Full text in Research Archive Show summary

  Many plankton and fish are attracted to artificial light, although they escape natural light during daytime. Potentially, this can be used to concentrate mesopelagic organisms in an area to a degree which allow caged fish to feed on mesopelagic organisms instead of traditional feed. Various species of krill can be highly abundant in coastal areas where bottom depths allow deep, safe and dark habitats during daytime. Placing caged fish in a flux of krill with artificial light to lure them into the cages as feed for fish may be an ecologially efficient way of harvesting lower trophic organisms in the ocean. Here, I present an overview of the potential of such a system, with theoretical estimates of production capacity of fish in specific regions. The technology is emerging, and with it a need to understand the ecological effects of tapping at the bottom of the food chain.

• Opdal, Anders Martin Frugård (2025). Havet blir mørkere, men forskerne vet ikke helt hvorfor. ung.forskning.no. Full text in Research Archive Show summary

  Forskere ser at mindre lys slipper til i vannet.

• Opdal, Anders Martin Frugård (2025). Bjørnson, kjøttmeisen, Hjort og torsken. Naturen. ISSN 0028-0887. 149(1), p. 39–43. doi: 10.18261/naturen.149.1.5. Full text in Research Archive
• Opdal, Anders Martin Frugård; Jørgensen, Christian; Sivle, Lise Doksæter; Karlsen, Ørjan; Langbehn, Tom & Ljungström, Anna Jeja Gabriella [Show all 11 contributors for this article] (2025). Seasonal dynamics in ocean temperatures can give false impression of thermal bottleneck for spawning fish. Full text in Research Archive
• Opdal, Anders Martin Frugård (2024). The role of individual variation in a warming ocean. Full text in Research Archive
• Opdal, Anders Martin Frugård; Jørgensen, Christian; Sivle, Lise Doksæter; Karlsen, Ørjan; Langbehn, Tom & Ljungström, Anna Jeja Gabriella [Show all 11 contributors for this article] (2024). Seasonal dynamics in ocean temperatures can give false impression of thermal bottleneck for spawning fish. Full text in Research Archive
• Opdal, Anders Martin Frugård; Lindemann, Christian; Fiksen, Øyvind; Hessen, Dag Olav; Andersen, Tom & Aksnes, Dag Lorents (2024). Land use change and coastal water darkening drive synchronous dynamics in phytoplankton and fish phenology on centennial time scales. Full text in Research Archive
• Sandven, Håkon Johan; Hamre, Børge; Connan-McGinty, Stacey; Granskog, Mats; Opdal, Anders Martin Frugård & McKee, David (2024). Strong changes in Barents Sea light availability in last four decades due to sea ice decline. Full text in Research Archive
• Opdal, Anders Martin Frugård; Andersen, Tom; Hessen, Dag Olav; Lindemann, Christian & Aksnes, Dag Lorents (2023). Tracking freshwater browning and coastal water darkening from boreal forests to the Arctic Ocean. Full text in Research Archive
• Opdal, Anders Martin Frugård; Wright, Peter James; Blom, Geir; Höffle, Hannes; Lindemann, Christian & Kjesbu, Olav Sigurd (2023). Spawning fish maintain trophic synchrony across time and space beyond thermal drivers. Full text in Research Archive
• Hessen, Dag Olav & Opdal, Anders Martin Frugård (2023). Linking Forest to Fish: A Story of Coastal Darkening. SIL news (The International Association of Theoretical and Applied Limnology). doi: 10.5281/zenodo.8009398. Full text in Research Archive
• Opdal, Anders Martin Frugård; Lindemann, Christian; Fiksen, Øyvind; Hessen, Dag Olav; Andersen, Tom & Aksnes, Dag Lorents (2023). Tracking freshwater browning and coastal water darkening from boreal forests to the Arctic Ocean. Full text in Research Archive
• Opdal, Anders Martin Frugård; Lindemann, Christian; Fiksen, Øyvind; Hessen, Dag Olav; Andersen, Tom & Aksnes, Dag Lorents (2023). Land use change and coastal water darkening drive synchronous dynamics in phytoplankton and fish phenology on centennial time scales. Full text in Research Archive
• Opdal, Anders Martin Frugård; Wright, Peter James; Blom, Geir; Höffle, Hannes & Kjesbu, Olav Sigurd (2022). Behavioural plasticity offset thermal drivers of spawning phenology in cod. Full text in Research Archive
• Narayanappa, Devaraju; Nilsen, Irene Brox & Falk, Stefanie (2021). Avskoging og den indiske monsunen ("Deforestation and the indian monsoon"). blogg.forskning.no- søkelys på skogplantning. Full text in Research Archive
• Narayanappa, Devaraju; Berntsen, Terje Koren & Stordal, Frode (2021). Simulated runoff and river discharge in CTSM version 5.1: Evaluation over Scandinavia. Full text in Research Archive Show summary

  Reliable representation of terrestrial water and energy balance in global climate models is crucial to better understand the response of the hydrological cycle to climate change. Though the current generation of global climate models have improved substantially, they still fail to represent all terrestrial processes adequately. Specifically simulating runoff and river discharge are important for many applications such as water resources management and future water availability projections. In this study, we use the land surface model component of the Norwegian Earth System Model which is Community Land Model version 5 (CLM5) to evaluate against observation-based estimates of runoff and river discharge data of selected catchments data. For the latest three decades (1985-2015), we compare the CLM5 simulated grid-scale runoff with observation-based gridded runoff estimates (E-RUN version 1.1) and with data from the Global Runoff Data Centre (GRDC). CLM5 is also capable of simulating river discharge to the oceans through the Model for Scale Adaptive River Transport (MOSART) and is applicable across local, regional, and global scales. The 3-hourly 0.5o meteorological forcing for CLM5 was provided by the Global Soil Wetness Project version 3v1, an international land surface modeling project. We also compare the simulated river discharge data with selected station discharge data in Norway and Sweden. I will present the detailed evaluation results at the conference. Briefly, the evaluation analysis suggests the further calibration to hydrologic parameters is needed to improve simulations of runoff and river discharge, especially subsurface runoff.

• Narayanappa, Devaraju (2020). Vegetation atmosphere interactions in earth system models. Full text in Research Archive Show summary

  I have presented results from the idealized large-scale deforestation simulations performed using coupled global climate models. The focus was mainly on global temperature change and monsoonal rainfall changes. Increasing human activities altering the land surface at large-scale for agriculture, urbanization, firewood, and timber purposes. Today about 50% of the ice-free land surface is covered by crops or pastures and, in many parts of the world, we continue to expand these areas for food because the world’s population is growing (IPCC-SRCCL 2019). This continued land cover change (LCC) is one of the major drivers of regional and global climate change through altered biophysical (BPH; changes in physical characteristics such as albedo, evapotranspiration, and roughness) and biogeochemical (BGC; changes in atmospheric composition) processes and is increasingly recognized in today's assessments of anthropogenic impacts. In this presentation, I mostly discuss about biophysical effects of deforestation to understand the impact of large perturbations to global land cover. Specifically, if deforested areas are abandoned and forests are allowed to re-grow, will the climate system go back to its natural state? How long will it take for the climate system to reach a new equilibrium in such a case? What determines the time scale? Are there interactions between forests and the atmosphere that gets severely altered for large scale land cover change? Does the monsoon rainfall across the world alters due to large-scale deforestation? I have addressed these questions in this talk using simulations from Earth system models.

• Aarflot, Johanna Myrseth; Aksnes, Dag Lorents; Dalpadado, Padmini; Opdal, Anders Frugård & Fiksen, Øyvind (2020). Bathymetry Structures Predator-prey Dynamics between Zooplankton and Fish in Marine Pelagic Ecosystems. Full text in Research Archive
• Lindemann, Christian; Jørgensen, Christian; Fiksen, Øyvind & Aksnes, Dag Lorents (2020). Could long term shift in cod phenology be linked to terrestrial greening and coastal browning. Full text in Research Archive Show summary

  With climate warming, a widespread expectation is that events in spring, like flowering, bird migrations, and insect bursts, will occur earlier because temperature permits. What then, when data shows the opposite? Here we show a steady delay in spawning time of Northeast Arctic cod by more than 40 days between 1877 and 1980 – a period in which there is no regional trend in ocean temperatures. Our preliminary investigation point towards a potential link between increased terrestrial vegetation, via coastal water darkening to phytoplankton spring bloom and cod spawning time. Based on centennial observations of Secchi disk depth and phytoplankton concentrations, we find that the long-term reduction in coastal water clarity in these areas are primarily driven by other factors than phytoplankton, including dissolved organic matter of terrestrial origin. From a state-of-the-art water column model, we estimate that the reduction in water clarity alone would result in a 3 weeks delay in the phytoplankton spring bloom onset over the 20th century – in line with the delay in cod spawning time and opposite predictions from global warming. We hypothesize that the widespread, recent browning of lakes and rivers, primarily driven by land use change and increased precipitation and air temperature stimulating plant and forest growth, eventually drain to the coast, reducing coastal water clarity, affecting plankton growth conditions with implications for phenological events such as timing of the spring phytoplankton bloom and ultimately fish spawning time.

• Opdal, Anders Martin Frugård; Lindemann, Christian; Fiksen, Øyvind & Aksnes, Dag Lorents (2020). Could long term shift in cod phenology be linked to terrestrial greening and coastal browning. Full text in Research Archive
• Opdal, Anders Martin Frugård; Skjæraasen, Jon Egil & Jørgensen, Christian (2020). Fisk gyter ved bestemte temperaturer – atferd eller miljø. Full text in Research Archive

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