Arctic Sea Ice Retreat in 2007 Follows Thinning Trend

Journal of Climate (Impact Factor: 4.44). 01/2009; 22(1). DOI: 10.1175/2008JCLI2521.1


The minimum of Arctic sea ice extent in the summer of 2007 was unprecedented in the historical record. A coupled ice–ocean model is used to determine the state of the ice and ocean over the past 29 yr to investigate the causes of this ice extent minimum within a historical perspective. It is found that even though the 2007 ice extent was strongly anomalous, the loss in total ice mass was not. Rather, the 2007 ice mass loss is largely consistent with a steady decrease in ice thickness that began in 1987. Since then, the simulated mean September ice thickness within the Arctic Ocean has declined from 3.7 to 2.6 m at a rate of 0.57 m decade 1 . Both the area coverage of thin ice at the beginning of the melt season and the total volume of ice lost in the summer have been steadily increasing. The combined impact of these two trends caused a large reduction in the September mean ice concentration in the Arctic Ocean. This created conditions during the summer of 2007 that allowed persistent winds to push the remaining ice from the Pacific side to the Atlantic side of the basin and more than usual into the Greenland Sea. This exposed large areas of open water, resulting in the record ice extent anomaly.

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Available from: Axel Schweiger, Jul 10, 2014
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    • "The factors influencing storage and release relate to the wind stress curl over the central Arctic (Proshutinsky et al. 2009) that in ice-covered seas is modified by sea ice. Changes in the spatial distribution of sea ice and wind-stress curl contribute to a myriad of observed Arctic changes such as the shift in the boundary between Atlantic-and Pacific-derived waters (Morison et al. 1998); a shift in the position of the trans-polar drift (Rigor et al. 2002); retreat and return of the cold halocline in the Eurasian Basin (Alkire et al. 2007); reduced pack ice (Lindsay et al. 2009); changes in freshwater content (Polyakov et al. 2008; Rabe et al. 2014); increased run-off into the Eurasian sector (Peterson et al. 2002); and many more (White et al. 2007). Meanwhile, Arctic freshwater export impacts downstream deep water formation zones in the Greenland and Labrador Seas. "
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    ABSTRACT: Time series observations of velocity, salinity, pressure, and ice draft provide estimates of advective fluxes in Nares Strait from 2003 to 2009 at daily to interannual time scales. Velocity and salinity are integrated across the 36 km wide and 350 m deep channel for two distinct multi-year periods of sea ice cover. These observations indicate multi-year mean fluxes that range from 0.71±0.09 to 1.03±0.11 Sv (Sv=10 −6 m 3 s −1 =31,536 km 3 yr −1) for volume and from 32±5.7 to 54±9.3 mSv for oceanic freshwater relative to a salinity of 34.8 for the first 2003-06 and second 2007-09 periods, respectively. Advection of ice adds another 8±2 mSv or 260±70 km 3 per year to the freshwater export. Flux values are larger when the sea ice is mobile all year. About 75% of the oceanic volume and freshwater flux variability is correlated at daily to interannual time scales. Flux variability peaks at a 20-day time scale and correlates strongly with along-channel pressure gradients (r 2 = 0.68). The along-channel pressure gradient peaks in early spring when the sea ice is often motionless with higher sea level in the Arctic that drives the generally southward ocean circulation. Local winds contribute only when the sea ice is mobile when they explain 60% its variance (r 2 = 0.60). Observed annual to interannual change in the duration of motionless sea ice conditions impacts ocean stratification and freshwater flux while seasonal variations are small. [Accepted for publication, J.
    Journal of Physical Oceanography 08/2015; in press. DOI:10.1175/JPO-D-15-0093.1] · 2.86 Impact Factor
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    • "The mean sea ice thickness of the Arctic has been decreasing since the 1980s (Lindsay and Zhang, 2005; Rigor et al., 2004), and the sea ice extent reached minimum values in 2007 and 2008 (Lindsay et al., 2009). "
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    • "The Arctic pack ice region is undergoing dramatic changes due to global warming (e.g., IPCC, 2007; Jeffries and Richter-Menge, 2012). These changes not only affect 5 the extent and thickness of the Arctic sea ice (Lindsay et al., 2009), but also the influence of physical and chemical processes of the aerosols on the regional climate (e.g., Curry et al., 2000; Prenni et al., 2007). Herein, radiative effects of aerosol particles and aerosol–cloud interactions play a substantial role: aerosols interact with solar radiation directly by scattering or absorbing sunlight. "
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    ABSTRACT: Single-particle mass spectrometric measurements were carried out in the High Arctic north of 80° during summer 2008. The campaign took place onboard the icebreaker Oden and was part of the Arctic Summer Cloud Ocean Study (ASCOS). The instrument deployed was an Aerosol Time-of-Flight Mass Spectrometer (ATOFMS) that provides information on the chemical composition of individual particles and their mixing state in real-time. Aerosols were sampled in the marine boundary layer at stations in the open ocean, in the marginal ice zone, and in the pack ice region. The largest fraction of particles detected for subsequent analysis in the size range of the ATOFMS between approximately 200 nm to 3000 nm in diameter showed mass spectrometric patterns indicating an internal mixing state and a biomass burning and/or biofuel source. The majority of these particles were connected to an air mass layer of elevated particle concentration mixed into the surface mixed layer from the upper part of the marine boundary layer. The second largest fraction was represented by sea salt particles. The chemical analysis of the over-ice sea salt aerosol revealed tracer compounds that reflect chemical aging of the particles during their long-range advection from the marginal ice zone, or open waters south thereof prior to detection at the ship. From our findings we conclude that long-range transport of particles is one source of aerosols in the High Arctic. To assess the importance of long-range particle sources for aerosol-cloud interactions over the inner Arctic in comparison to local and regional biogenic primary aerosol sources, the chemical composition of the detected particles was analyzed for indicators of marine biological origin. Only a~minor fraction showed chemical signatures of potentially ocean-derived primary particles of that kind. However, a chemical bias in the ATOFMS's detection capabilities observed during ASCOS might suggest a presence of a particle type of unknown composition and source. In general, the study suffered from low counting statistics due to the overall small number of particles found in this pristine environment, the small sizes of the prevailing aerosol below the detection limit of the ATOFMS and its low hit rate. To our knowledge, this study reports on the first in-situ single-particle mass spectrometric measurements in the marine boundary layer of the High-Arctic pack-ice region.
    Atmospheric Chemistry and Physics 12/2013; 14(1). DOI:10.5194/acpd-14-593-2014 · 5.05 Impact Factor
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