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Absorption, Reflection, Transmission of Solar Radiation
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Radiative forcing and albedo feedback from the Northern Hemisphere cryosphere between 1979 and 2008
Abstract: The extent of snow cover and sea ice in the Northern Hemisphere has declined since 1979, coincident with hemispheric warming and indicative of a positive feedback of surface reflectivity on climate. This albedo feedback of snow on land has been quantified from observations at seasonal timescales, and century-scale feedback has been assessed using climate models. However, the total impact of the cryosphere on radiative forcing and albedo feedback has yet to be determined from measurements. Here we assess the influence of the Northern Hemisphere cryosphere on Earth's radiation budget at the top of the atmosphere—termed Cryosphere radiative forcing—by synthesizing a variety of remote sensing and field measurements. We estimate mean Northern Hemisphere forcing at -4.6 to -2.2 W m-2, with a peak in May of -9.0 ± 2.7 W m-2. We find that cyrospheric cooling declined by 0.45 W m-2 from 1979 to 2008, with nearly equal contributions from changes in land snow cover and sea ice. On the basis of these observations, we conclude that the albedo feedback from the Northern Hemisphere Cryosphere falls between 0.3 and 1.1 W m-2 K-1, substantially larger than comparable estimates obtained from 18 climate models.
Citation: Flanner, M. G., K. M. Shell, M. Barlage, D. K. Perovich, and M. A. Tschudi (2011), Radiative forcing and albedo feedback from the Northern Hemisphere cryosphere between 1979 and 2008, Nature Geoscience, 4, 151-155, doi: 10.1038/ngeo1062.
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The spatial distribution of solar radiation under a melting Arctic sea ice cover
Abstract: The sea ice cover of the Chukchi and Beaufort Seas is currently undergoing a fundamental shift from multiyear ice to first-year ice. Field observations of sea ice physical and optical properties were collected in this region during June–July 2010, revealing unexpectedly complex spatial distributions of solar radiation under the melt-season ice cover. Based on our optical measurements of first-year ice, we found the under-ice light field in the upper ocean to be spatially heterogeneous and dependent on wavelength, ice thickness, and the areal and geometric distribution of melt ponded and bare ice surfaces. Much of the observed complexity in radiation fields arose because the transmission of light through ponded ice was generally an order of magnitude greater than through bare, unponded ice. Furthermore, while many sites exhibited a consistent, exponential decay in light transmission through both ponded and bare ice surfaces, light transmission under bare ice was also observed to increase with depth (reaching maximum values ∼5–10 m below the bottom of the ice). A simple geometric model shows these transmission peaks are a result of scattering in the ice and the interspersion of bare and ponded sea ice surfaces. These new observations of complex radiation fields beneath melt-season first-year sea ice have significant implications for biological production, biogeochemical processes, and the heat balance of sea ice and under-ice ocean waters and should be carefully considered when modeling these sea ice-related phenomena.
Citation: Frey, K. E., D. K. Perovich, and B. Light (2011), The spatial distribution of solar radiation under a melting Arctic sea ice cover, Geophysical Research Letters, 38, L22501, doi:10.1029/2011GL049421.
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Energy budget of first-year Arctic sea ice in advanced stages of melt
Abstract: During an 8 day drift in July–August 2012 in the Nansen Basin, all components of the energy budget of melting first-year sea ice were observed. Absorption of solar radiation by the ice and ponds was the largest source of energy to the ice at almost all times during the drift. However, oceanic heat flux also provided significant heating and dominated during one wind event. Longwave fluxes provided a relatively small cooling effect, and atmospheric heat fluxes were negligible. The aggregate scale albedo of this younger, thinner ice was significantly lower than at Surface Heat Budget of the Arctic Ocean (SHEBA), and the transmittance was significantly higher here, despite similar pond and open water fractions. The oceanic heat flux was only half of the solar flux through the ice to the water, producing warm water near the surface that might delay ice growth in autumn, an important effect of the transition to thinner first-year ice in the high Arctic.
Citation: Hudson, S. R., M. A. Granskog, A. Sundfjord, A. Randelhoff, A. H. H. Renner, and D. V. Divine (2013), Energy budget of first-year Arctic sea ice in advanced stages of melt, Geophysical Research Letters, 40, 2679–2683, doi:10.1002/grl.50517.
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Changes in Arctic sea ice result in increasing light transmittance and absorption
Abstract: Arctic sea ice has declines and become thinner and younger (more seasonal) during the last decade. Once consequence of this is that the surface energy budget of the Arctic Ocean is changing. While the role of surface albedo has been studied intensively, it is still widely unknown how much light penetrates through sea ice into the upper ocean, affecting sea-ice mass balance, ecosystems, and geochemical processes. HEre we present the first large-scale under-ice light measurement, operating spectral radiometers on a remotely operated vehicle (ROV) under Arctic sea ice in summer. This data set is used to produce an Arctic-wide map of light distribution under summer sea ice. Our results show that transmittance through first-year ice (FYI, 0.11) was almost thee times larger than through multi-year ice (MYI, 0.04), and that this is mothly caused by the larger melt-pond covergae of FYI (42 vs 23%). Also, energy absorption was 50% larger in FYI than in MYI. Thus, a continuation of the observed sea-ice changes will increase the amount of light penetrating into the Arctic Ocean, enhancing sea-ice melt and affecting sea-ice and upper-ocean ecosystems.
Citation: Nicolaus, M., C. Katlein, J. Maslanik, and S. Hendricks (2012), Changes in Arctic sea ice result in increasing light transmittance and absorption, Geophysical Research Letters, 39, L24501, doi:10.1029/2012GL053738.
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Variability of light transmission through Arctic land-fast sea ice during spring
Abstract: The amount of solar radiation transmitted through Arctic sea ice is determined by the thickness and physical properties of snow and sea ice. Light transmittance is highly variable in space and time since thickness and physical properties of snow and sea ice are highly heterogeneous on variable time and length scales. We present field measurements of under-ice irradiance along transects under undeformed land-fast sea ice at Barrow, Alaska (March, May, and June 2010). The measurements were performed with a spectral radiometer mounted on a floating under-ice sled. The objective was to quantify the spatial variability of light transmittance through snow and sea ice, and to compare this variability along its seasonal evolution. Along with optical measurements, snow depth, sea ice thickness, and freeboard were recorded, and ice cores were analyzed for chlorophyll a and particulate matter. Our results show that snow cover variability prior to onset of snow melt causes as much relative spatial variability of light transmittance as the contrast of ponded and white ice during summer. Both before and after melt onset, measured transmittances fell in a range from one third to three times the mean value. In addition, we found a twentyfold increase of light transmittance as a result of partial snowmelt, showing the seasonal evolution of transmittance through sea ice far exceeds the spatial variability. However, prior melt onset, light transmittance was time invariant and differences in under-ice irradiance were directly related to the spatial variability of the snow cover.
Citation: Nicolaus, M., C. Petrich, S. R. Hudson, and M. A. Granskog (2013), Variability of light transmission through Arctic land-fast sea ice during spring, The Cryosphere, 7, 977-986, doi:10.5194/tc-7-977-2013.
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Methylmercury photodegradation influenced by sea-ice cover in Arctic marine ecosystems
Abstract: Atmospheric deposition of mercury to remote areas has increased threefold since pre-industrial times. Mercury deposition is particularly pronounced in the Arctic. Following deposition to surface oceans and sea ice, mercury can be converted into methylmercury, a biologically accessible form of the toxin, which biomagnifies along the marine food chain. Mass-independent fractionation of mercury isotopes accompanies the photochemical breakdown of methylmercury to less bioavailable forms in surface waters. Here we examine the isotopic composition of mercury in seabird eggs collected from colonies in the North Pacific Ocean, the Bering Sea and the western Arctic Ocean, to determine geographical variations in methylmercury breakdown at northern latitudes. We find evidence for mass-independent fractionation of mercury isotopes. The degree of mass-independent fractionation declines with latitude. Foraging behaviour and geographic variations in mercury sources and solar radiation fluxes were unable to explain the latitudinal gradient. However, mass-independent fractionation was negatively correlated with sea-ice cover. We conclude that sea-ice cover impedes the photochemical breakdown of methylmercury in surface waters, and suggest that further loss of Arctic sea ice this century will accelerate sunlight-induced breakdown of methylmercury in northern surface waters.
Citation: Point, D., J. E. Sonke, R. D. Day, D. G. Roseneau, K. A. Hobson, S. S. Vander Pol, A. J. Moors, R. S. Pugh, O. F. X. Donard, and P. R. Becker (2011), Methylmercury photodegradation influenced by sea-ice cover in Arctic marine ecosystems, Nature Geoscience, 4, 188-194, doi: 10.1038/ngeo1049.
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Sea Ice Extent & Thickness
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Estimation of sea ice thickness in Ross and Weddell Seas from SSMI/I brightness temperatures
Abstract: In polar regions, ocean–atmosphere interactions are strongly influenced by sea ice and its thickness. Since satellite passive microwave observations became available in the 1970s, significant progress has been made in the study of snow depth and sea ice concentration and extent in these regions. Estimating sea-ice thickness (SIT), instead, turned out to be considerably more difficult. We present a new empirical algorithm to estimate SIT in the Ross and Weddell Seas from Special Sensor Microwave/Imager brightness temperatures. This algorithm combines brightness temperature polarization difference and ratio values to obtain SIT for seasonal ice up to a thickness of about 90 cm during freezing conditions. A series of filters accounts for open water, new ice, and snow on sea ice. Our SIT estimates are consistent with colocated visual ship-based SIT observations made according to the Antarctic Sea Ice Processes and Climate project, showing linear correlation values between 0.73 and 0.96 and root-mean-square-error values between 14 and 24 cm. The seasonal development of the region average SIT derived with our approach agrees with the corresponding values derived from U.S. National Ice Center ice charts. Comparison with collocated polynya distribution maps suggests that the algorithm could be optimized for its performance with regard to SIT values around 50 cm and that a closer investigation of the snow impact on the SIT retrieval is required.
Citation: Aulicino G., G. Fusco, S. Kern, and G. Budillon (2013), Estimation of sea ice thickness in Ross and Weddell Seas from SSM/I brightness temperatures, TGRS, 52, 8, doi: 10.1109/TGRS.2013.2279799.
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On the 2012 record low Arctic sea ice cover: Combined impact of preconditioning and an August storm
Abstract: A new record low Arctic sea ice extent for the satellite era, 3.4 × 106 km2, was reached on 13 September 2012; and a new record low sea ice area, 3.0 × 106 km2, was reached on the same date. Preconditioning through decades of overall ice reductions made the ice pack more vulnerable to a strong storm that entered the central Arctic in early August 2012. The storm caused the separation of an expanse of 0.4 × 106 km2 of ice that melted in total, while its removal left the main pack more exposed to wind and waves, facilitating the main pack's further decay. Future summer storms could lead to a further acceleration of the decline in the Arctic sea ice cover and should be carefully monitored.
Citation: Parkinson, C. L., and J. C. Comiso (2013), On the 2012 record low Arctic sea ice cover: Combined impact of preconditioning and an August storm, Geophysical Research Letters, 40, 1356-1361, doi:10.1002/grl.50349.
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The impact of an intense summer cyclone on 2012 Arctic sea ice retreat
Abstract: This model study examines the impact of an intense early August cyclone of the 2012 record low Arctic sea ice extent. The cyclone passed when Arctic sea ice was thin and the simulated Arctic ice volumes had already declined ~40% from the 2007-2011 mean. The thin sea ice pack and the presence of ocean heat in the near surface temperature maximum layer created conditions that made the ice particularly vulnerable to storms. During the storm, ice volume decreased about twice as fast as usual, owing largely to a quadrupling in bottom melt caused by increased upward ocean heat transport. This increased ocean heat flux was due to enhanced mixing in the oceanic boundary layer, driven by strong winds and rapid ice movement. A comparison with a sensitivity simulation driven by reduced wind speeds during the cyclone indicates that cyclone-enhanced bottom melt strongly reduces ice extent for about 2 weeks, with a declining effect afterward. The simulated Arctic sea ice extent minimum in 2012 is reduced by the cyclone but only by 0.15× 106 km2 (4.4%). Thus, without the storm, 2012 would still have produced a record minimum.
Citation: Zhang, J., R. Lindsay, A. Schweiger, and M. Steele (2013), The impact of an intense summer cyclone on 2012 Arctic sea ice retreat, Geophysical Research Letters, 40, 720-726, doi:10.1002/grl.50190.
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The impact of winds and sea surface temperatures on the Barents Sea ice extent, a statistical approach
Abstract: An analysis was made of the processes controlling the incidence of sea ice in the Barents Sea for the period 1979-2010. The influence of atmospheric circulation and ocean temperature on the interannual variability of sea-ice extent (SIE) in the Barents Sea was investigated using sea-ice concentrations obtained from passive microwave satellite imagery, sea surface temperatures (SSTs), and NCEP-NCAR sea level pressure (SLP) data. Data from April and September were analysed, the months when SIE in the Barents Sea is respectively at its maximum and minimum. The strongest negative correlations (-0.65 to -0.77) were found between the SIE in the Barents Sea and SST in the regions most influenced by Atlantic Water. The patterns of distribution of correlation coefficients between interannual variability of SIE in the Barents Sea and SLP over the Nordic Seas and Siberia showed two well-defined SLP zones: one with a high positive correlation (0.60 to 0.65) over the Norwegian and Greenland seas, and a zone with high negative correlation (-0.60 to -0.63) in the area of western Siberia. We conclude that winds induced by changes in SLP gradient between these zones affect both the redistribution of sea ice and the advection of heat into the Barents Sea.
Citation: Pavlova, O., V. Pavlov, and S. Gerland (2014), The impact of winds and sea surface temperatures on the Barents Sea ice extent, a statistical approach, Journal of Marine Systems, 130, 248-255, doi:10.1016/j.jmarsys.2013.02.011.
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Mixing/Turbulence
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Observations of turbulent mixing and hydrography in the marginal ice zone of the Barents Sea
Abstract: Measurements of hydrography, currents, microstructure shear, and temperature were made at ice drift stations in the marginal ice zone (MIZ) of the northern Barents Sea. Highly variable mixing regimes were observed within and below the pycnocline. Elevated turbulent dissipation (5-15 × 10-7 W kg-1) was associated with strong vertical shear between the surface layer and the subsurface currents, as well as strong tidal flow over shallow topography. Dissipation in the pycnocline was enhanced at stations with strong wind forcing. During drifts under relatively calm wind and away from strong fronts and abrupt topography, station-mean dissipation values were up to a factor 50 lower and double diffusion contributed significantly to the vertical heat flux where hydrography favored diffusive layering. Independent measures of turbulent length scale from density overturns compared well with those inferred from the dissipation measurements. The variability of dissipation was better captured using a scaling by shear suggested for shelves rather than shear variance models appropriate to the deep open ocean. Sufficiently resolved patches of enhanced temperature microstructure used in combination with dissipation measurements suggest mixing efficiency of Rf ~ 0.2 for patches stable to double diffusion, comparable to the conventional upper bound of Rf ~ 0.17. Mixing efficiency for double-diffusive convection favorable cases is found to be significantly larger, Rf ~ 0.36. Water mass modification and fluxes of nutrients and dissolved carbon were found to have large local variability in accordance with the observed variability of vertical mixing in the MIZ.
Citation: Sundfjord, A., I. Fer, Y. Kasajima, and H. Svendsen (2007), Observations of turbulent mixing and hydrography in the marginal ice zone of the Barents Sea, Journal of Geophysical Research, 112, C05008, doi:10.1029/2006JC003524.
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Early spring oceanic heat fluxes and mixing observed from drift stations north of Svalbard
Abstract: From several drifting ice stations north of Svalbard, Norway, observations were made in early spring of the ocean turbulent characteristics in the upper 150 m using a microstructure profiles and close to the under-ice surface using eddy correlation instrumentation. The dataset is used to obtain average heat fluxes at the ice-water interface, in the mixed layer, across the main pycnocline, as well over different water masses in the region. The results are contrasted with proximity to the branches of the warm and saline Atlantic water current, the West Spitsbergen Current (WSC), which is the main oceanis heat and salinity source both to the region and to the Arctic Ocean. Hydrographic properties show that the surface water mass modification is typically due to atmospheric cooling with relatively less infleunce of ice melting. Surface heat fluxes of O(100) W m-2 are found within the branches of the WSC and over shelf areas with elevated levels of mixing due to strong tides. Away from the shelves and WSC, however, ocean-to-ice turbulent heat fluxes are typical of the central Arctic. Deeper in the water column, entrainment from below together with equally important horizontal advection and diffusion increase the heat content of the mixed layer and contribute to the heat flux maximum in the upper layers. The results in this study emphasize the importance of mixing along the boundaries, over shelves, and topography for the cooling of the Atlantic water layer in the Arctic in general, and for the regional heat budget, hence the ice cover and cooling of the WSC north of Svalbard, in particular.
Citation: Sirevaag, A., and I. Fer (2009), Early spring oceanic heat fluxes and mixing observed from drift stations north of Svalbard, Journal of Physical Oceanography, 39, 3049-3069, doi:10.1175/2009JPO4172.1.
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Mixing, heat fluxes and heat content evolution of the Arctic Ocean mixed layer
Abstract: A comprehensive measurement program was conducted during 16 days of a 3 week long ice pack drift, from 15 August to 1 September 2008 in the central Amundsen Basin, Arctic Ocean. The data, sampled as part of the Arctic Summer Cloud Ocean Study (ASCOS), included upper ocean stratification, mixing and heat transfer as well as transmittance of solar radiation through the ice. The observations give insight into the evolution of the upper layers of the Arctic Ocean in the transition period from melting to freezing. The ocean mixed layer was found to be heated from above and, for summer conditions, the net heat flux through the ice accounted for 22% of the observed change in mixed layer heat content. Heat was mixed downward within the mixed layer and a small, downward heat flux across the base of the mixed layer accounted for the accumulated heat in the upper cold halocline during the melt season. On average, the ocean mixed layer was cooled by an ocean heat flux at the ice/ocean interface (1.2 W m-2) and heated by solar radiation through the ice (-2.6 W m-2). An abrupt change in surface conditions halfways into the drift due to freezing and snowfall showed distinct signatures in the data set and allowed for inferences and comparisons to be made for cases of contrasting forcing conditions. Transmittance of solar radiations was reduced by 59% in the latter period. From hydrographic observations obtained earlier in the melting season, in the same region, we infer a total fresh water equivalent of 3.3 m accumulated in the upper ocean, which together with the observed saltier winter mixed layer indicates a transition towards a more seasonal ice cover in the Arctic.
Citation: Sirevaag, A., S. de la Rosa, I. Fer, M. Nicolaus, M. Tjernsttrom, and M.G. McPhee (2011), Mixing, heat fluxes and heat content evolution of the Arctic Ocean mixed layer, Ocean Science, 7, 335-349, doi:10.5194/os-7-335-2011.
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Influences of the ocean surface mixed layer and thermohaline stratification on Arctic Sea ice in the central Canada Basin
Abstract: Variations in the Arctic central Canada Basin mixed layer properties are documented based on a subset of nearly 6500 temperature and salinity profiles acquired by Ice-Tethered Profilers during the period summer 2004 to summer 2009 and analyzed in conjunction with sea ice observations from ice mass balance buoys and atmosphere‐ocean heat flux estimates. The July–August mean mixed layer depth based on the Ice‐Tethered Profiler data averaged 16 m (an overestimate due to the Ice‐Tethered Profiler sampling characteristics and present analysis procedures), while the average winter mixed layer depth was only 24 m, with individual observations rarely exceeding 40 m. Guidance interpreting the observations is provided by a 1‐D ocean mixed layer model. The analysis focuses attention on the very strong density stratification at the base of the mixed layer in the Canada Basin that greatly impedes surface layer deepening and thus limits the flux of deep ocean heat to the surface that could influence sea ice growth/ decay. The observations additionally suggest that efficient lateral mixed layer restratification processes are active in the Arctic, also impeding mixed layer deepening.
Citation: Toole, J. M., M. -L. Timmermans, D. K. Perovich, R. A. Krishfield, A. Proshutinsky, and J. A. Richter-Menge (2010), Influences of the ocean surface mixed layer and thermohaline stratification on Arctic Sea ice in the central Canada Basin, Journal of Geophysical Research, 115, C10018, doi:10.1029/2009JC005660.
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Biological/Ecological Importance
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Massive Phytoplankton Blooms Under Arctic Sea Ice
Abstract: Science Brevia do not contain abstracts.
Citation: Arrigo, K. R. et al. (2012), Massive Phytoplankton Blooms Under Arctic Sea Ice, Science, 336, doi: 10.1126/science.1215065.
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Floating Ice-Algal Aggregates below Melting Arctic Sea Ice
Abstract: During two consecutive cruises to the Eastern Central Arctic in late summer 2012, we observed floating algal aggregates in the melt-water layer below and between melting ice floes of first-year pack ice. The macroscopic (1-15 cm in diameter) aggregates had a mucous consistency and were dominated by typical ice-associated pinnate diatoms embedded within the mucous matrix. Aggregates maintained buoyancy and accumulated just above a strong pycnocline that separated meltwater and seawater layers. We were able, for the first time, to obtain quantitative abundance and biomass estimates of these aggregates. Although their biomass and production on a square metre basis was small compared to ice-algal blooms, the floating ice-algal aggregates supported high levels of biological activity on the scale of the individual aggregate. In addition they constituted a food source for the ice-associated fauna as revealed by pigments indicative of zooplankton grazing, high abundance of naked ciliates, and ice amphipods associated with them. During the Arctic melt season, these floating aggregates likely play an important ecological role in an otherwise impoverished near-surface sea ice environment. Our findings provide important observations and measurements of a unique aggregate-based habitat during the 2012 record sea ice minimum year.
Citation: Assmy P., J. K. Ehn, M. Fernández-Méndez, H. Hop, C. Katlein, et al. (2013), Floating Ice-Algal Aggregates below Melting Arctic Sea Ice, PLoS ONE, 8, 10, doi:10.1371/journal.pone.0076599
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Diatoms and biomarkers evidence for major changes in sea ice conditions prior the instrumental period in Antarctic Peninsula
Abstract: The Antarctic Peninsula (AP) has been identified as one of the most rapidly warming region on Earth. Satellite monitoring currently allows for a detailed understanding of the relationship between sea ice extent and duration and atmospheric and oceanic circulations in this region. However, our knowledge on ocean-ice-atmosphere interactions is still relatively poor for the period extending beyond the last 30 years. Here, we describe environmental conditions in Northwestern and Northeastern Antarctic Peninsula areas over the last century using diatom census counts and diatom specific biomarkers (HBIs) in two marine sediment multicores (MTC-38C and -18A, respectively). Diatom census counts and HBIs show abrupt changes between 1935 and 1950, marked by ocean warming and sea ice retreat in both sides of the AP. Since 1950, inferred environmental conditions do not provide evidence for any trend related to the recent warming but demonstrate a pronounced variability on pluri-annual to decadal time scale. We propose that multi-decadal sea ice variations over the last century are forced by the recent warming, while the annual-to-decadal variability is mainly governed by synoptic and regional wind fields in relation with the position and intensity of the atmospheric low-pressure trough around the AP. However, the positive shift of the SAM since the last two decades cannot explain the regional trend observed in this study, probably due to the effect of local processes on the response of our biological proxies.
Citation: Barbara, L., X. Crosta, S. Schmidt, and G. Massé (2010), Diatoms and biomarkers evidence for major changes in sea ice conditions prior the instrumental period in Antarctic Peninsula, Quaternary Science Reviews, 79, 99-110.
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Consequences of changing sea-ice cover for primary and secondary producers in the European Arctic shelf seas: Timing, quantity, and quality
Abstract: The Arctic ice cover poses severe limitations on the productive period of marine autotrophs that form the base of the marine food web. Sea-ice algae begin to grow in early spring within and underneath the ice, producing a substantial biomass despite very low light intensities. Pelagic algal blooms, in contrast, normally occur after ice breakup, at high latitudes as late as July–September. The timing of these blooms is crucial for the quantity and quality of primary and secondary production, and therefore for the transfer of energy and matter to higher trophic levels. Recent findings from Rijpfjorden, north-eastern Svalbard indicate that ice algae, rather than pelagic algae, trigger the reproduction of Arctic zooplankton around Svalbard. The key herbivore in Arctic shelf seas, the copepod Calanus glacialis, timed its seasonal migration, foraging, and reproduction to the ice algal bloom, which preceded the pelagic algal bloom by two months. The growth of this secondary producer's offspring, however, was dependent on the later bloom of phytoplankton and higher sea-water temperatures. In 2007, reproduction and growth of C. glacialis and the primary production regime matched perfectly. The persistent ice cover in summer 2008, however, led to a mismatch between the pelagic algal bloom and the growth of the new copepod generation, resulting in a fivefold lower biomass of C. glacialis in August 2008 compared to 2007. The initiation of the ice algal bloom is mainly determined by the solar angle, whereas the pelagic algal bloom requires more light and is therefore governed to a larger degree by ice thinning and the unpredictable ice breakup. We conclude that both a too early as well as a too late ice breakup can cause a mismatch between primary and secondary producers, with negative consequences for the entire lipid-based Arctic marine food web.
Citation: Leu, E., J. E. Søreide, D. O. Hessen, S. Falk-Petersen, and J. Berge (2011), Consequences of changing sea-ice cover for primary and secondary producers in the European Arctic shelf seas: Timing, quantity, and quality, Progress in Oceanography, 90, 18–32, doi:10.1016/j.pocean.2011.02.004.
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Timing of blooms, algal food quality and Calanus glacialis reproduction and growth in a changing Arctic
Abstract: The Arctic bloom consists of two distinct categories of primary producers, ice algae growing within and on the underside of the sea ice, and phytoplankton growing in open waters. Long chain omega-3 fatty acids, a subgroup of polyunsaturated fatty acids (PUFAs) produced exclusively by these algae, are essential to all marine organisms for successful reproduction, growth, and development. During an extensive field study in the Arctic shelf seas, we followed the seasonal biomass development of ice algae and phytoplankton and their food quality in terms of their relative PUFA content. The first PUFA-peak occurred in late April during solid ice cover at the onset of the ice algal bloom, and the second PUFA-peak occurred in early July just after the ice break-up at the onset of the phytoplankton bloom. The reproduction and growth of the key Arctic grazer Calanus glacialis perfectly coincided with these two bloom events. Females of C. glacialis utilized the high-quality ice algal bloom to fuel early maturation and reproduction, whereas the resulting offspring had access to ample high-quality food during the phytoplankton bloom 2 months later. Reduction in sea ice thickness and coverage area will alter the current primary production regime due to earlier ice break-up and onset of the phytoplankton bloom. A potential mismatch between the two primary production peaks of high-quality food and the reproductive cycle of key Arctic grazers may have negative consequences for the entire lipid-driven Arctic marine ecosystem.
Citation: Søreide, J. E., E. Leu, J. Berge, M. Graeve, and S. Falk-Petersen (2010), Timing of blooms, algal food quality and Calanus glacialis reproduction and growth in a changing Arctic, Global Change Biology, 16, 3154–3163, doi: 10.1111/j.1365-2486.2010.02175.x.
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