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1. DMS emissions from the Arctic marginal ice zone

   https://doi.org/10.1525/ elementa.2020.00113  

   Galí, M. (July 2021, Elementa)

   Phytoplankton blooms in the Arctic marginal ice zone (MIZ) can be prolific dimethylsulfide (DMS) producers, thereby influencing regional aerosol formation and cloud radiative forcing. Here we describe the distribution of DMS and its precursor dimethylsulfoniopropionate (DMSP) across the Baffin Bay receding ice edge in early summer 2016. Overall, DMS and total DMSP (DMSPt) increased towards warmer waters of Atlantic origin concurrently with more advanced ice-melt and bloom stages. Relatively high DMS and DMSPt (medians of 6.3 and 70 nM, respectively) were observed in the surface layer (0–9 m depth), and very high values (reaching 74 and 524 nM, respectively) at the subsurface biomass maximum (15–30 m depth). Microscopic and pigment analyses indicated that subsurface DMS and DMSPt peaks were associated with Phaeocystis pouchetii, which bloomed in Atlantic-influenced waters and reached unprecedented biomass levels in Baffin Bay. In surface waters, DMS concentrations and DMS:DMSPt ratios were higher in the MIZ (medians of 12 nM and 0.15, respectively) than in fully ice-covered or ice-free conditions, potentially associated with enhanced phytoplanktonic DMSP release and bacterial DMSP cleavage (high dddP:dmdA gene ratios). Mean sea–air DMS fluxes (micromol m–2 d–1) increased from 0.3 in ice-covered waters to 10 in open waters (maximum of 26) owing to concurrent trends in near-surface DMS concentrations and physical drivers of gas exchange. Using remotely sensed sea-ice coverage and a compilation of sea–air DMS flux data, we estimated that the pan-Arctic DMS emission from the MIZ was 5–13 Gg S yr–1. North of 80 oN, DMS emissions might have increased by around 10% yr–1 between 2003 and 2014, likely exceeding open-water emissions in June and July. We conclude that DMS emissions from the MIZ must be taken into account to evaluate plankton-climate feedbacks in the Arctic. 

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2. The JCMT BISTRO Survey: Revealing the Diverse Magnetic Field Morphologies in Taurus Dense Cores with Sensitive Submillimeter Polarimetry

   https://doi.org/10.3847/2041-8213/abeb1c  

   Eswaraiah, Chakali; Li, Di; Furuya, Ray S.; Hasegawa, Tetsuo; Ward-Thompson, Derek; Qiu, Keping; Ohashi, Nagayoshi; Pattle, Kate; Sadavoy, Sarah; Hull, Charles L.; et al (May 2021, The Astrophysical Journal Letters)

   Abstract We have obtained sensitive dust continuum polarization observations at 850 μ m in the B213 region of Taurus using POL-2 on SCUBA-2 at the James Clerk Maxwell Telescope as part of the B -fields in STar-forming Region Observations (BISTRO) survey. These observations allow us to probe magnetic field ( B -field) at high spatial resolution (∼2000 au or ∼0.01 pc at 140 pc) in two protostellar cores (K04166 and K04169) and one prestellar core (Miz-8b) that lie within the B213 filament. Using the Davis–Chandrasekhar–Fermi method, we estimate the B -field strengths in K04166, K04169, and Miz-8b to be 38 ± 14, 44 ± 16, and 12 ± 5 μ G, respectively. These cores show distinct mean B -field orientations. The B -field in K04166 is well ordered and aligned parallel to the orientations of the core minor axis, outflows, core rotation axis, and large-scale uniform B -field, in accordance with magnetically regulated star formation via ambipolar diffusion taking place in K04166. The B -field in K04169 is found to be ordered but oriented nearly perpendicular to the core minor axis and large-scale B -field and not well correlated with other axes. In contrast, Miz-8b exhibits a disordered B -field that shows no preferred alignment with the core minor axis or large-scale field. We found that only one core, K04166, retains a memory of the large-scale uniform B -field. The other two cores, K04169 and Miz-8b, are decoupled from the large-scale field. Such a complex B -field configuration could be caused by gas inflow onto the filament, even in the presence of a substantial magnetic flux. 

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3. Spectral attenuation of ocean waves in pack ice and its application in calibrating viscoelastic wave-in-ice models

   https://doi.org/10.5194/tc-14-2053-2020  

   Cheng, Sukun; Stopa, Justin; Ardhuin, Fabrice; Shen, Hayley H. (January 2020, The Cryosphere)

   null (Ed.)

   Abstract. We investigate a case of ocean waves through a pack icecover captured by Sentinel-1A synthetic aperture radar (SAR) on 12 October 2015 in the Beaufort Sea. The study domain is 400 km by 300 km, adjacent to amarginal ice zone (MIZ). The wave spectra in this domain were reported in aprevious study (Stopa et al., 2018b). In that study, the authors divided thedomain into two regions delineated by the first appearance of leads (FAL)and reported a clear change of wave attenuation of the total energy betweenthe two regions. In the present study, we use the same dataset to study thespectral attenuation in the domain. According to the quality of SAR-retrieved wave spectrum, we focus on a range of wave numbers corresponding to9–15 s waves from the open-water dispersion relation. Wefirst determine the apparent attenuation rates of each wave number by pairingthe wave spectra from different locations. These attenuation rates slightlyincrease with increasing wave number before the FAL and become lower and moreuniform against wave number in thicker ice after the FAL. The spectralattenuation due to the ice effect is then extracted from the measuredapparent attenuation and used to calibrate two viscoelastic wave-in-icemodels. For the Wang and Shen (2010b) model, the calibrated equivalent shearmodulus and viscosity of the pack ice are roughly 1 order of magnitudegreater than that in grease and pancake ice reported in Cheng et al. (2017).These parameters obtained for the extended Fox and Squire model are muchgreater, as found in Mosig et al. (2015) using data from the Antarctic MIZ.This study shows a promising way of using remote-sensing data with largespatial coverage to conduct model calibration for various types of icecover.Highlights. Three key points: The spatial distribution of wave number and spectral attenuation in pack iceare analyzed from SAR-retrieved surface wave spectra. The spectral attenuation rate of 9–15 s waves varies around10−5 m2 s−1, with lower values in thicker semicontinuous ice fieldswith leads. The calibrated viscoelastic parameters are greater than those found inpancake ice. 

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4. MrSARP: A Hierarchical Deep Generative Prior for SAR Image Super-resolution

   https://doi.org/10.1109/RadarConf2351548.2023.10149659  

   Agarwal, Tushar; Sugavanam, Nithin; Ertin, Emre (May 2023, Proceedings of 2023 IEEE Radar Conference (RadarConf23))

   Generative models learned from training using deep learning methods can be used as priors in under-determined inverse problems, including imaging from sparse set of measurements. In this paper, we present a novel hierarchical deep-generative model MrSARP for SAR imagery that can synthesize SAR images of a target at different resolutions jointly. MrSARP is trained in conjunction with a critic that scores multi resolution images jointly to decide if they are realistic images of a target at different resolutions. We show how this deep generative model can be used to retrieve the high spatial resolution image from low resolution images of the same target. The cost function of the generator is modified to improve its capability to retrieve the input parameters for a given set of resolution images. We evaluate the model's performance using three standard error metrics used for evaluating super-resolution performance on simulated data and compare it to upsampling and sparsity based image super-resolution approaches. 

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5. Identifying fractal geometry in Arctic marginal ice zone dynamics

   https://doi.org/10.1088/1748-9326/adc01e  

   Sherman, Julie; Strong, Courtenay; Golden, Kenneth_M (March 2025, Environmental Research Letters)

   Abstract The Arctic marginal ice zone (MIZ) is the transitional region between dense pack ice and open ocean. As an increasingly important component of the polar marine environment, recent investigations have focused on changes in MIZ size and location as the climate has warmed. Fractal geometry offers a universal measure of complexity, shape, and self-similarity across scales, and a powerful tool for characterizing MIZ evolution. Here we analyze the fractal dimension of the Arctic MIZ boundary and find a pronounced seasonal cycle that is repeated almost exactly each year, with a sharp maximum in late summer. The long-term trend is slight, with a decrease of less than 2% over the satellite era, while MIZ width has increased over the same period by almost 40%. Our results have important implications for climatic and ecological processes which depend critically on MIZ geometry. We demonstrate thermodynamic feedbacks through statistical analysis and provide context for future applications. 

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