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1. The North Icelandic Jet and its relationship to the North Icelandic Irminger Current

   https://doi.org/10.1357/002224017822109505  

   Pickart, Robert S. ; Spall, Michael A. ; Torres, Daniel J. ; Våge, Kjetil ; Valdimarsson, Hedinn ; Nobre, C. ; Moore, G. W. ; Jonsson, Steingrimur ; Mastropole, Dana ( September 2017 , Journal of Marine Research)
2. Alongstream, seasonal and interannual variability of the North Icelandic Irminger Current and East Icelandic Current around Iceland

   Casanova-Masjoan, M ; Perez-Hernandez, M ; Pickart, R ; Valdimarsson, H ; Macrander, A ; Velez-Belchi, P ; Grisolia-Santos, D ; Torres, D ; Jonsson, S ; Vage, K ( January 2020 , Journal of geophysical research)
3. Along‐Stream, Seasonal, and Interannual Variability of the North Icelandic Irminger Current and East Icelandic Current Around Iceland

   https://doi.org/10.1029/2020JC016283  

   Casanova‐Masjoan, M. ; Pérez‐Hernández, M. D. ; Pickart, R. S. ; Valdimarsson, H. ; Ólafsdóttir, S. R. ; Macrander, A. ; Grisolía‐Santos, D. ; Torres, D. J. ; Jónsson, S. ; Våge, K. ; et al ( September 2020 , Journal of Geophysical Research: Oceans)

   Data from repeat hydrographic surveys over the 25‐year period 1993 to 2017, together with satellite altimetry data, are used to quantify the temporal and spatial variability of the North Icelandic Irminger Current (NIIC), East Icelandic Current (EIC), and the water masses they advect around northern Iceland. We focus on the warm, salty Atlantic Water (AW) flowing northward through Denmark Strait and the cooler, fresher, denser Atlantic‐origin Overflow Water (AtOW) which has circulated cyclonically around the rim of the Nordic Seas before being advected to the Iceland slope via the EIC. The absolute geostrophic velocities reveal that approximately half of the NIIC recirculates just north of Denmark Strait, while the remaining half merges with the EIC to form a single current that extends to the northeast of Iceland, with no further loss in transport of either component. The AW percentage decreases by 75% over this distance, while the AtOW percentage is higher than that of the AW in the merged current. The NIIC and merged NIIC‐EIC are found to be baroclinically unstable, which causes the flow to become increasingly barotropic as it progresses around Iceland. A seasonal accounting of the water masses within the currents indicates that only in springtime is the NIIC dominated by AW inflow north of Denmark Strait. Overall, there is considerably more seasonal and along‐stream variability in the properties of the flow prior to the merging of the NIIC and EIC. Over the 25‐year time period, the NIIC became warmer, saltier, and increased in volume transport.

    

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4. Sensory environment affects Icelandic threespine stickleback's anti-predator escape behaviour

   https://doi.org/10.1098/rspb.2022.0044  

   Ålund, Murielle ; Harper, Brooke ; Kjærnested, Sigurlaug ; Ohl, Julian E. ; Phillips, John G. ; Sattler, Jessica ; Thompson, Jared ; Varg, Javier E. ; Wargenau, Sven ; Boughman, Janette W. ; et al ( April 2022 , Proceedings of the Royal Society B: Biological Sciences)

   Human-induced changes in climate and habitats push populations to adapt to novel environments, including new sensory conditions, such as reduced visibility. We studied how colonizing newly formed glacial lakes with turbidity-induced low-visibility affects anti-predator behaviour in Icelandic threespine sticklebacks. We tested nearly 400 fish from 15 populations and four habitat types varying in visibility and colonization history in their reaction to two predator cues (mechano-visual versus olfactory) in high versus low-visibility light treatments. Fish reacted differently to the cues and were affected by lighting environment, confirming that cue modality and light levels are important for predator detection and evasion. Fish from spring-fed lakes, especially from the highlands (likely more diverged from marine fish than lowland fish), reacted fastest to mechano-visual cues and were generally most active. Highland glacial fish showed strong responses to olfactory cues and, counter to predictions from the flexible stem hypothesis, the greatest plasticity in response to light levels. This study, leveraging natural, repeated invasions of novel sensory habitats, (i) illustrates rapid changes in anti-predator behaviour that follow due to adaptation, early life experience, or both, and (ii) suggests an additional role for behavioural plasticity enabling population persistence in the face of frequent changes in environmental conditions. 

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5. The Emergence of the North Icelandic Jet and Its Evolution from Northeast Iceland to Denmark Strait

   https://doi.org/10.1175/JPO-D-19-0088.1  

   Semper, Stefanie ; Våge, Kjetil ; Pickart, Robert S. ; Valdimarsson, Héðinn ; Torres, Daniel J. ; Jónsson, Steingrímur ( October 2019 , Journal of Physical Oceanography)

   The North Icelandic Jet (NIJ) is an important source of dense water to the overflow plume passing through Denmark Strait. The properties, structure, and transport of the NIJ are investigated for the first time along its entire pathway following the continental slope north of Iceland, using 13 hydrographic/velocity surveys of high spatial resolution conducted between 2004 and 2018. The comprehensive dataset reveals that the current originates northeast of Iceland and increases in volume transport by roughly 0.4 Sv (1 Sv ≡ 10 6 m 3 s −1 ) per 100 km until 300 km upstream of Denmark Strait, at which point the highest transport is reached. The bulk of the NIJ transport is confined to a small area in Θ– S space centered near −0.29° ± 0.16°C in Conservative Temperature and 35.075 ± 0.006 g kg −1 in Absolute Salinity. While the hydrographic properties of this transport mode are not significantly modified along the NIJ’s pathway, the transport estimates vary considerably between and within the surveys. Neither a clear seasonal signal nor a consistent link to atmospheric forcing was found, but barotropic and/or baroclinic instability is likely active in the current. The NIJ displays a double-core structure in roughly 50% of the occupations, with the two cores centered at the 600- and 800-m isobaths, respectively. The transport of overflow water 300 km upstream of Denmark Strait exceeds 1.8 ± 0.3 Sv, which is substantially larger than estimates from a year-long mooring array and hydrographic/velocity surveys closer to the strait, where the NIJ merges with the separated East Greenland Current. This implies a more substantial contribution of the NIJ to the Denmark Strait overflow plume than previously envisaged. 

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