Interception of atmospheric fluxes by Arctic sea ice: Evidence from cosmogenic⁷Be

Abstract

[1] The natural cosmogenic radionuclide 7 Be (T 1/2 = 53.4 d) is supplied to the surface ocean from the atmosphere and, in the Arctic Ocean, can be used as a tracer of the efficiency with which sea ice intercepts the atmospheric fluxes of chemical species and of the importance of ice as a transport mechanism for particulate matter and chemical species. Analyses of 7 Be in samples of surface water, surface sea ice, water beneath the ice, sea ice sediments, and precipitation from the Eurasian Basin of the Arctic Ocean show that the fraction of sea ice coverage determines the amount of 7 Be in the surface water. When sea ice coverage is <40%, the 7 Be inventory in the upper ocean (130 AE 19 Bq m À2 ) is in good agreement with that expected from the inventory from 7 Be atmospheric flux (128 AE 21 Bq m À2 ). In contrast, when ice coverage is >80%, the water column inventory drops to 58 AE 20 Bq m À2 . The 7 Be inventory in sea ice is 39 AE 23 Bq m À2 , and mass balance calculations show that sea ice can intercept 30 AE 18% of the atmospheric flux of 7 Be during the studied period. We suggest that other atmospherically transported contaminants should be similarly intercepted. 7 Be in the ice also can be used to estimate that the annual transport and release of sediment to the ablation area of the Fram Strait is $500 g m À2 , a value comparable to previously measured fluxes in sediment traps deployed in the area.

Carbon export fluxes and export efficiency in the central Arctic during the record sea‐ice minimum in 2012: a joint 234Th/238U and 210Po/210Pb study

“…13.2 6 0.9 700 6 120 0.9 6 0.9 1.7 6 0.4 100 6.7 6 0.5 104 6 9 0.7 6 0.8 0. [Cochran et al, 1995b;Moran et al, 1997Moran et al, , 2005Moran and Smith, 2000;Amiel et al, 2002;Coppola et al, 2002;Baskaran et al, 2003;Ma et al, 2005;Trimble and Baskaran, 2005;Lepore et al, 2007;Lalande et al, 2007Lalande et al, , 2008Amiel and Cochran, 2008;Yu et al, 2010Yu et al, , 2012Cai et al, 2010;Gustafsson and Andersson, 2012;Le Moigne et al, 2015, this study]. Black circles indicate the results obtained in this study.…”

“…In the Arctic, sea ice intercepts and accumulates atmospheric fluxes of chemical species, such as 210 Pb, during its transit through the ocean [ Masqué et al ., ; Cámara‐Mor et al ., ] and, therefore, sea‐ice melting may increase 210 Pb activities in surface waters where that occurs [ Roberts et al ., ; Masqué et al ., ; Chen et al ., ]. One might wonder whether sea‐ice melting may significantly impact the 210 Po and 210 Pb activities in seawater and, thus, affect the use of the 210 Po proxy.…”

Influence of organic matter on the adsorption of 210Pb, 210Po and 7Be and their fractionation on nanoparticles in seawater

“…In comparison, SiO 2 had a considerably stronger affinity for 7 Be. These results are consistent with those of field observations (e.g., Honeyman and Santschi, 1989;Chase et al, 2002;Chase and Anderson, 2004) and laboratory studies using marine diatoms (e.g., Chuang et al, 2014) or microparticles (e.g., Yang et al, 2013). The log K c values of 7 Be in the presence of MOCs (4.01-6.25) were also comparable to field values (3.00 to 6.63) as compiled in Yang et al (2013).…”

“…Similar to 210 Po and 210 Pb,7 Be and 10 Be (T 1/2 = 1.5 × 10 6 yr) derived mainly from atmospheric deposition, have also been widely used to constrain particle transport (Kumar et al, 1995;Feng et al, 1999aFeng et al, , 1999bFeng et al, , 1999cBaskaran and Swarzenski, 2007;Cámara-Mor et al, 2011;Huang et al, 2013), atmospheric deposition of trace elements, and vertical mixing of water masses (Kadko et al, 1996(Kadko et al, , 2011(Kadko et al, , 2015. However, the specific key particulate components that are responsible for the removal of Be isotopes from seawater remain unclear.…”

Scavenging and fractionation of particle-reactive radioisotopes 7Be, 210Pb and 210Po in the atmosphere

“…Due to its high particle-reactivity and unique source function, 7 Be could be used as a tracer for a wide range of processes in the atmosphere (Gaffney et al, 1994;Turekian and Graustein, 2003;Ioannidou and Papastefanou, 2006;Papastefanou, 2006;Dibb, 2007) as well as in the aquatic systems (e.g., Silker, 1972; http://dx.doi.org/10.1016/j.gca.2016.05.039 0016-7037/Ó 2016 Elsevier Ltd. All rights reserved. Young and Silker, 1980;Masqué et al, 2007;Kadko and Prospero, 2011;Cámara-Mor et al, 2011).…”