Sofia Ribeiro

Functional traits are central to species fitness and ecosystem resilience, yet our understanding of climate change impacts on functional diversity is limited by a paucity of long-term data. Here, we apply a trait framework to a marine sedimentary ancient DNA record from the high Arctic spanning the past ~8300 years. This period includes warm and cold oscillations, including a phase when regional summer temperatures were higher than today. Our framework uncovers heterogenous responses to climate variability among functional groups, and millennial-scale diversity pulses synchronous with swings in the dominant mode of the Arctic Oscillation. Furthermore, protists show a temperature-size relationship with trade-offs under different temperature and sea ice regimes. By extending trait-based approaches into the paleogenetic realm, our study provides biodiversity reconstructions at unprecedented resolution, captures diversity components inaccessible from the fossil record alone, and opens new avenues for understanding how marine ecosystems respond to climate forcing across millennial timescales.

Nares Strait, a marine gateway connecting the Arctic Ocean with northern Baffin Bay, is characterised by the formation of seasonal ice bridges between Canada and Greenland that prevent the southward export of multiyear sea ice. Recent observations indicate increasing instability in sea-ice formation particularly evident in Kane Basin, which either freezes over or remains open during winter and spring, depending on ice-bridge dynamics. Kane Basin is influenced by contrasting ocean currents in its eastern and western sides, as well as by the Humboldt Glacier, Greenland's widest marine-terminating glacier. Kane Basin is a critical region due to its pronounced sensitivity to cryospheric and oceanic changes. However, its long-term environmental history, particularly in the eastern sector, remains poorly constrained prior to the satellite era. Here, we present two multi-proxy sediment core records from opposite sides of Kane Basin, spanning the 18th century to the present, that we compare with Humboldt Glacier solid ice discharge and retreat since 1965 CE. Clear spatial differences are evident across the basin in terms of sediment delivery, primary productivity, and organic matter sources. Both records also reveal temporal changes, transitioning from cold sea-surface conditions with extensive sea-ice cover during the Little Ice Age (peaking around 1900 CE), towards more open and stratified waters, accompanied by a shift towards higher primary production from approximately 1950 CE to the present.

Nares Strait, a marine gateway connecting the Arctic Ocean with northern Baffin Bay, is characterised by the formation of a seasonal ice bridge between Canada and Greenland, that prevents the southward export of multiyear sea ice. Recent observations indicate increasing instability in sea-ice formation, particularly evident in Kane Basin, which either freezes over or remains open during winter and spring depending on ice-bridge dynamics. The Kane Basin is influenced by contrasting ocean currents in its eastern and western sides, as well as by the Humboldt Glacier, Greenland’s widest marine-terminating glacier. Kane Basin is a critical region due to its pronounced sensitivity to cryospheric and oceanic changes. However, its long-term environmental history, particularly in the eastern sector, remains poorly constrained prior to the satellite era. Here, we present two multi-proxy sediment core records from opposite sides of Kane Basin, spanning from the 18th century to the present, that we compare with Humboldt Glacier frontal positions since 1965 CE. Clear spatial differences are evident across the basin in terms of sediment delivery, primary productivity, and the source of organic matter. Both records also reveal temporal changes, transitioning from cold sea-surface conditions with extensive sea ice during the Little Ice Age (peaking around 1900 CE), towards more open and stratified waters, accompanied by increased primary production from approximately 1950 CE to the present.

Nares Strait, a marine gateway connecting the Arctic Ocean with northern Baffin Bay, is characterised by the formation of a seasonal ice bridge between Canada and Greenland, that prevents the southward export of multiyear sea ice. Recent observations indicate increasing instability in sea-ice formation, particularly evident in Kane Basin, which either freezes over or remains open during winter and spring depending on ice-bridge dynamics. The Kane Basin is influenced by contrasting ocean currents in its eastern and western sides, as well as by the Humboldt Glacier, Greenland’s widest marine-terminating glacier. Kane Basin is a critical region due to its pronounced sensitivity to cryospheric and oceanic changes. However, its long-term environmental history, particularly in the eastern sector, remains poorly constrained prior to the satellite era. Here, we present two multi-proxy sediment core records from opposite sides of Kane Basin, spanning from the 18th century to the present, that we compare with Humboldt Glacier frontal positions since 1965 CE. Clear spatial differences are evident across the basin in terms of sediment delivery, primary productivity, and the source of organic matter. Both records also reveal temporal changes, transitioning from cold sea-surface conditions with extensive sea ice during the Little Ice Age (peaking around 1900 CE), towards more open and stratified waters, accompanied by increased primary production from approximately 1950 CE to the present.

Nares Strait, a marine gateway connecting the Arctic Ocean with northern Baffin Bay, is characterised by the formation of a seasonal ice bridge between Canada and Greenland, that prevents the southward export of multiyear sea ice. Recent observations indicate increasing instability in sea-ice formation, particularly evident in Kane Basin, which either freezes over or remains open during winter and spring depending on ice-bridge dynamics. The Kane Basin is influenced by contrasting ocean currents in its eastern and western sides, as well as by the Humboldt Glacier, Greenland’s widest marine-terminating glacier. Kane Basin is a critical region due to its pronounced sensitivity to cryospheric and oceanic changes. However, its long-term environmental history, particularly in the eastern sector, remains poorly constrained prior to the satellite era. Here, we present two multi-proxy sediment core records from opposite sides of Kane Basin, spanning from the 18th century to the present, that we compare with Humboldt Glacier frontal positions since 1965 CE. Clear spatial differences are evident across the basin in terms of sediment delivery, primary productivity, and the source of organic matter. Both records also reveal temporal changes, transitioning from cold sea-surface conditions with extensive sea ice during the Little Ice Age (peaking around 1900 CE), towards more open and stratified waters, accompanied by increased primary production from approximately 1950 CE to the present.

Nares Strait, a marine gateway connecting the Arctic Ocean with northern Baffin Bay, is characterised by the formation of a seasonal ice bridge between Canada and Greenland, that prevents the southward export of multiyear sea ice. Recent observations indicate increasing instability in sea-ice formation, particularly evident in Kane Basin, which either freezes over or remains open during winter and spring depending on ice-bridge dynamics. The Kane Basin is influenced by contrasting ocean currents in its eastern and western sides, as well as by the Humboldt Glacier, Greenland’s widest marine-terminating glacier. Kane Basin is a critical region due to its pronounced sensitivity to cryospheric and oceanic changes. However, its long-term environmental history, particularly in the eastern sector, remains poorly constrained prior to the satellite era. Here, we present two multi-proxy sediment core records from opposite sides of Kane Basin, spanning from the 18th century to the present, that we compare with Humboldt Glacier frontal positions since 1965 CE. Clear spatial differences are evident across the basin in terms of sediment delivery, primary productivity, and the source of organic matter. Both records also reveal temporal changes, transitioning from cold sea-surface conditions with extensive sea ice during the Little Ice Age (peaking around 1900 CE), towards more open and stratified waters, accompanied by increased primary production from approximately 1950 CE to the present.

Retreating sea ice and freshening surface waters are rapidly changing Arctic coastal environments. To predict the impacts of cryosphere change, it is essential to understand ecosystem variability beyond the instrumental era. Diatoms and dinoflagellate resting cysts have been abundantly used to reconstruct past marine conditions. Our understanding of microfossil species' ecologies is predominantly based on ecophysiological studies, the spatial distribution of species in surface sediments in relation to surface‐ocean conditions and sediment‐core studies. However, little is known about their seasonal ecologies and how biotic interactions impact species abundances. Here, we present sediment trap records of diatom and dinocyst succession over 4 years in a seasonally ice‐covered Northeast Greenland fjord. We found highly seasonal diatom blooms and dinocyst production, but no clear separation in the timing between sea‐ice indicating and open‐water species fluxes. The interannual variation was not linked with the timing of sea‐ice breakup. Instead, we linked higher production of heterotrophic dinocysts with high river discharge, while the highest diatom fluxes were often recorded during relatively low river discharge, suggesting that land‐derived meltwaters controlled the blooms through stratification and light limitation. Thus, while we were not able to detect detailed species‐environment dynamics due to the resolution of the trap data, our results indicate that the limitation of light and nutrients due to river discharge may override the impacts of sea‐surface temperature and sea‐ice cycle. We highlight that land‐derived inputs should be considered alongside other parameters of sea‐surface conditions when using diatoms and dinocysts as paleoecological proxies in Arctic fjord settings.

Arctic marine ecosystems have undergone notable reconfigurations in response to Holocene climate and environmental changes. Yet our understanding of how marine mammal occurrence was impacted remains limited, due to their relative scarcity in the fossil record. We reconstruct the occurrence of marine mammals across the past 12,000 years through detections based on sedimentary ancient DNA from four marine sediment cores collected around Northern Greenland, and integrate the findings with local and regional environmental proxy records. Our findings indicate a close association between marine mammals at densities detectable in marine sediments and the deglaciation of high Arctic marine environments at the onset of the Holocene. Further, we identify air temperature and changes in sea ice cover as significant drivers of community change across time. Several marine mammals are detected in the sediments earlier than in the fossil record, for some species by several thousand years. During the Early-to-Mid Holocene, a period of warmer climate, we record northward distribution shifts of temperate and low-arctic marine mammal species. Our findings provide unique, long-term baseline data on the occurrence of marine mammals around Northern Greenland, enabling insights into past community dynamics and the effects of Holocene climatic shifts on the region’s marine ecosystems.

Decreasing sea-ice extent and retreating and thinning of Greenland’s glaciers are rapidly changing Arctic coastal environments by warming and freshening the sea surface and impacting light availability. In Arctic fjords, productivity is significantly influenced by the position of glacier termini, and the present retreat of the Greenland Ice Sheet will increase the number of fjords surrounded only by land-terminating glaciers in the future. This will most likely affect the productivity and ecosystem structure of coastal marine areas. To predict future cryosphere change and its impacts, it is essential to understand climate and ecosystem variability beyond the instrumental era. Here we present a high-resolution reconstruction of coastal marine ecosystem change and its linkages to terrestrial freshwater and organic matter inputs in Young Sound fjord, Northeast Greenland, over the Holocene. The reconstructions are based on marine sediment-core proxies: organic-walled palynomorphs (including e.g. dinoflagellate cysts and pollen), sympagic and pelagic biomarkers (highly branched isoprenoids and sterols) and a set of geochemical indicators (sediment organic carbon, nitrogen, their stable isotopes, and biogenic silica). The results suggest a relatively cold early Holocene with extensive sea-ice cover and low productivity. Warmer and more variable conditions take hold after approximately 9 kyr with increasing productivity, species richness and terrestrial freshwater inputs, with colder conditions seen after approximately 3.5 kyr with high productivity coupled with higher ice-algae contribution. The results also indicate that this near-shore marine ecosystem is clearly influenced by local forcings, such as terrestrial freshwater and organic matter inputs, suggesting that the continuous melting of the Greenland Ice Sheet will affect marine productivity and ecosystem structure in Greenland’s fjord systems, with potential impacts on biodiversity and sustainability of fisheries.