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1. Seasonality and timing of sea ice mass balance and heat fluxes in the Arctic transpolar drift during 2019–2020

   https://doi.org/10.1525/elementa.2021.000089  

   Lei, Ruibo ; Cheng, Bin ; Hoppmann, Mario ; Zhang, Fanyi ; Zuo, Guangyu ; Hutchings, Jennifer K. ; Lin, Long ; Lan, Musheng ; Wang, Hangzhou ; Regnery, Julia ; et al ( January 2022 , Elementa: Science of the Anthropocene)

   Sea ice growth and decay are critical processes in the Arctic climate system, but comprehensive observations are very sparse. We analyzed data from 23 sea ice mass balance buoys (IMBs) deployed during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition in 2019–2020 to investigate the seasonality and timing of sea ice thermodynamic mass balance in the Arctic Transpolar Drift. The data reveal four stages of the ice season: (I) onset of ice basal freezing, mid-October to November; (II) rapid ice growth, December–March; (III) slow ice growth, April–May; and (IV) melting, June onward. Ice basal growth ranged from 0.64 to 1.38 m at a rate of 0.004–0.006 m d–1, depending mainly on initial ice thickness. Compared to a buoy deployed close to the MOSAiC setup site in September 2012, total ice growth was about twice as high, due to the relatively thin initial ice thickness at the MOSAiC sites. Ice growth from the top, caused by surface flooding and subsequent snow-ice formation, was observed at two sites and likely linked to dynamic processes. Snow reached a maximum depth of 0.25 ± 0.08 m by May 2, 2020, and had melted completely by June 25, 2020. The relativelymore »early onset of ice basal melt on June 7 (±10 d), 2019, can be partly attributed to the unusually rapid advection of the MOSAiC floes towards Fram Strait. The oceanic heat flux, calculated based on the heat balance at the ice bottom, was 2.8 ± 1.1 W m–2 in December–April, and increased gradually from May onward, reaching 10.0 ± 2.6 W m–2 by mid-June 2020. Subsequently, under-ice melt ponds formed at most sites in connection with increasing ice permeability. Our analysis provides crucial information on the Arctic sea ice mass balance for future studies related to MOSAiC and beyond.« less
2. 90 years of Arctic Ocean Exploration at the Woods Hole Oceanographic Institution

   https://doi.org/10.29006/1564-2291.JOR-2020.48(3).10  

   Proshutinsky, A.Yu. ; Toole, J.M. ; Krishfield, R.A. ; Anderson, D.M. ; Ashjian, C.J. ; Baggeroer, A.B. ; Freitag, L.E. ; Pickart, R.S. ; von der Heydt, K. ( October 2020 , Journal of Oceanological Research)

   In 2020, the Woods Hole Oceanographic Institution (WHOI) celebrates 90 years of research, education, and exploration of the World Ocean. Since inception this has included Arctic studies. In fact, WHOI’s first technical report is on the oceanographic data obtained during the submarine “Nautilus” polar expedition in 1931. In 1951 and 1952, WHOI scientists supervised the collection of hydrographic data during the U.S. Navy SkiJump I & II expeditions utilizing ski-equipped aircraft landings in the Beaufort Sea, and inferred the Beaufort Gyre circulation cell and existence of a mid-Arctic ridge. Later classified studies, particularly concerning under-ice acoustics, were conducted by WHOI personnel from Navy and Air Force ice camps. With the advent of simple satellite communications and positioning, WHOI oceanographers began to deploy buoys on sea ice to obtain surface atmosphere, ice, and upper ocean time series data in the central Arctic beginning in 1987. Observations from these first systems were limited technologically to discrete depths and constrained by power considerations, satellite throughput, as well as high costs. As technologies improved, WHOI developed the drifting Ice-Tethered Profiler (ITP) to obtain vertically continuous upper ocean data several times per day in the ice-covered basins and telemeter the data back in near realmore »time to the lab. Since the 1980s, WHOI scientists have also been involved in geological, biological, ecological and geochemical studies of Arctic waters, typically from expeditions utilizing icebreaking vessels, or air supported drifting platforms. Since the 2000s, WHOI has maintained oceanographic moorings on the Beaufort Shelf and in the deep Canada Basin, the latter an element of the Beaufort Gyre Observing System (BGOS). BGOS maintains oceanographic moorings via icebreaker, and conducts annual hydrographic and geochemical surveys each summer to document the Beaufort Gyre freshwater reservoir that has changed significantly since earlier investigations from the 1950s–1980s. With the experience and results demonstrated over the past decades for furthering Arctic research, WHOI scientists are well positioned to continue to explore and study the polar oceans in the decades ahead« less
3. Spatiotemporal evolution of melt ponds on Arctic sea ice

   https://doi.org/10.1525/elementa.2021.000072  

   Webster, Melinda A. ; Holland, Marika ; Wright, Nicholas C. ; Hendricks, Stefan ; Hutter, Nils ; Itkin, Polona ; Light, Bonnie ; Linhardt, Felix ; Perovich, Donald K. ; Raphael, Ian A. ; et al ( January 2022 , Elementa: Science of the Anthropocene)

   Melt ponds on sea ice play an important role in the Arctic climate system. Their presence alters the partitioning of solar radiation: decreasing reflection, increasing absorption and transmission to the ice and ocean, and enhancing melt. The spatiotemporal properties of melt ponds thus modify ice albedo feedbacks and the mass balance of Arctic sea ice. The Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition presented a valuable opportunity to investigate the seasonal evolution of melt ponds through a rich array of atmosphere-ice-ocean measurements across spatial and temporal scales. In this study, we characterize the seasonal behavior and variability in the snow, surface scattering layer, and melt ponds from spring melt to autumn freeze-up using in situ surveys and auxiliary observations. We compare the results to satellite retrievals and output from two models: the Community Earth System Model (CESM2) and the Marginal Ice Zone Modeling and Assimilation System (MIZMAS). During the melt season, the maximum pond coverage and depth were 21% and 22 ± 13 cm, respectively, with distribution and depth corresponding to surface roughness and ice thickness. Compared to observations, both models overestimate melt pond coverage in summer, with maximum values of approximately 41% (MIZMAS) and 51%more »(CESM2). This overestimation has important implications for accurately simulating albedo feedbacks. During the observed freeze-up, weather events, including rain on snow, caused high-frequency variability in snow depth, while pond coverage and depth remained relatively constant until continuous freezing ensued. Both models accurately simulate the abrupt cessation of melt ponds during freeze-up, but the dates of freeze-up differ. MIZMAS accurately simulates the observed date of freeze-up, while CESM2 simulates freeze-up one-to-two weeks earlier. This work demonstrates areas that warrant future observation-model synthesis for improving the representation of sea-ice processes and properties, which can aid accurate simulations of albedo feedbacks in a warming climate.« less
4. The seasonal phases of an Arctic lagoon reveal the discontinuities of pH variability and CO₂ flux at the air–sea interface

   https://doi.org/10.5194/bg-18-1203-2021  

   Miller, Cale A. ; Bonsell, Christina ; McTigue, Nathan D. ; Kelley, Amanda L. ( January 2021 , Biogeosciences)

   Abstract. The western Arctic Ocean, including its shelves and coastal habitats, has become a focus in ocean acidification research over the past decade as thecolder waters of the region and the reduction of sea ice appear to promote the uptake of excess atmospheric CO2. Due to seasonal sea icecoverage, high-frequency monitoring of pH or other carbonate chemistry parameters is typically limited to infrequent ship-based transects duringice-free summers. This approach has failed to capture year-round nearshore carbonate chemistry dynamics which is modulated by biological metabolismin response to abundant allochthonous organic matter to the narrow shelf of the Beaufort Sea and adjacent regions. The coastline of the Beaufort Seacomprises a series of lagoons that account for > 50 % of the land–sea interface. The lagoon ecosystems are novel features that cycle between“open” and “closed” phases (i.e., ice-free and ice-covered, respectively). In this study, we collected high-frequency pH, salinity,temperature, and photosynthetically active radiation (PAR) measurements in association with the Beaufort Lagoon Ecosystems – Long Term Ecological Research program – for an entire calendar yearin Kaktovik Lagoon, Alaska, USA, capturing two open-water phases and one closed phase. Hourly pH variability during the open-water phases are someof the fastest rates reported, exceeding 0.4 units. Baseline pH varied substantially between themore »open phase in 2018 and open phase in 2019 from ∼ 7.85to 8.05, respectively, despite similar hourly rates of change. Salinity–pH relationships were mixed during all three phases, displaying nocorrelation in the 2018 open phase, a negative correlation in the 2018/19 closed phase, and a positive correlation during the 2019 open phase. The high frequency of pH variabilitycould partially be explained by photosynthesis–respiration cycles as correlation coefficients between daily average pH and PAR were 0.46 and 0.64for 2018 and 2019 open phases, respectively. The estimated annual daily average CO2 efflux (from sea to atmosphere) was5.9 ± 19.3 mmolm-2d-1, which is converse to the negative influx of CO2 estimated for the coastal Beaufort Seadespite exhibiting extreme variability. Considering the geomorphic differences such as depth and enclosure in Beaufort Sea lagoons, furtherinvestigation is needed to assess whether there are periods of the open phase in which lagoons are sources of carbon to the atmosphere, potentiallyoffsetting the predicted sink capacity of the greater Beaufort Sea.« less
5. The Cyclonic Mode of Arctic Ocean Circulation

   https://doi.org/10.1175/JPO-D-20-0190.1  

   Morison, James ; Kwok, Ron ; Dickinson, Suzanne ; Andersen, Roger ; Peralta-Ferriz, Cecilia ; Morison, David ; Rigor, Ignatius ; Dewey, Sarah ; Guthrie, John ( April 2021 , Journal of Physical Oceanography)

   null (Ed.)

   Abstract Arctic Ocean surface circulation change should not be viewed as the strength of the anticyclonic Beaufort Gyre. While the Beaufort Gyre is a dominant feature of average Arctic Ocean surface circulation, empirical orthogonal function analysis of dynamic height (1950–89) and satellite altimetry–derived dynamic ocean topography (2004–19) show the primary pattern of variability in its cyclonic mode is dominated by a depression of the sea surface and cyclonic surface circulation on the Russian side of the Arctic Ocean. Changes in surface circulation after Arctic Oscillation (AO) maxima in 1989 and 2007–08 and after an AO minimum in 2010 indicate the cyclonic mode is forced by the AO with a lag of about 1 year. Associated with a one standard deviation increase in the average AO starting in the early 1990s, Arctic Ocean surface circulation underwent a cyclonic shift evidenced by increased spatial-average vorticity. Under increased AO, the cyclonic mode complex also includes increased export of sea ice and near-surface freshwater, a changed path of Eurasian runoff, a freshened Beaufort Sea, and weakened cold halocline layer that insulates sea ice from Atlantic water heat, an impact compounded by increased Atlantic Water inflow and cyclonic circulation at depth. The cyclonic mode’s connectionmore »with the AO is important because the AO is a major global scale climate index predicted to increase with global warming. Given the present bias in concentration of in situ measurements in the Beaufort Gyre and Transpolar Drift, a coordinated effort should be made to better observe the cyclonic mode.« less