Ice core records of biomass burning tracers ( levoglucosan , dehydroabietic and 1 vanillic acids ) from Aurora Peak in Alaska since 1660 s : A new dimension of 2 forest fire activities in the Northern Hemisphere 3 4

15 A 180 m long (ca. 274 years) ice core was drilled in the saddle of the Aurora 16 Peak of Alaska (63.52°N; 146.54°W, elevation: 2,825 m). The ice core samples were 17 melt, concentrated and then derivatized with N,O-bis-(trimethylsilyl) 18 trifluoroacetamide with 1% trimethylsilyl chloride and pyridine followed by gas 19 chromatography/mass spectrometry analyses. Levoglucosan, dehydroabietic acid, and 20 vanillic acid are reported for the first time from the alpine glacier to better understand 21 historical biomass burning activities in the source region of southern Alaska. These 22 organic compounds showed higher concentrations with many sporadic peaks in the 23 1660s-1830s, 1913, and 2005. Moreover, there are few discrepancies of higher spikes 24 among them after the 1970s with sporadic peaks in 1994-2007 for dehydroabietic acid. 25 Historical trends of levoglucosan, dehydroabietic and vanillic acid showed that 26 biomass burning activities from resin and lignin in boreal conifer trees, other higher 27 plants and grasses were significant before the 1840s and after the 1970s in the source 28 regions of southern Alaska, being different from previous ice core studies. Long29 range atmospheric transport could be important for levoglucosan compared to 30 dehydroabietic acid in the North Pacific Rim (NPR). We found weak or no 31 correlations of levoglucosan with NO2 (r=0.06), NO3 (0.04), nss-SO4 2(0.08), nss-K + 32 (0.11), and NH4 + (0.11) from the same ice core, suggesting that these anions and 33 cations do not represent a gleaming signal of biomass burning activities in the source 34 regions for southern Alaska. Hence, this study revels a new dimension of biomass 35 burning periodic cycles in the NPR. 36 37 Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2019-139 Manuscript under review for journal Atmos. Chem. Phys. Discussion started: 6 March 2019 c © Author(s) 2019. CC BY 4.0 License.

Biomass burning activities such as forest fires and residential heating have some extent on climate change effect (Keywood et al., 2011;Whitlow et al., 1994).Many studies have shown that there is some discrepancy of temporal and spatial biomass burning activities (Kawamura et al., 2012;Whitlow et al., 1994;Kaplan et al., 2010 and references therein) in the Northern and Southern Hemisphere (NH/SH).These studies found different atmospheric transport patterns from source region to sampling site for different ice core records (Whitlow et al., 1994), which can alter the glaciochemical cycle in the NH and SH.

Materials and Methods
An ice core (180 m deep, 274 years old) was drilled in the saddle of the Aurora Peak of southern Alaska, which is located at 63.52°N, 146.54°W, elevation: 2,825 m (Figure 1).This 180 m long core was divided into ~50 cm pieces and directly transported to the laboratory of the Institute of Low Temperature Science (ILTS), Hokkaido University, Japan and stored in a dark cold room at -20ºC until analysis.
The ice core ages were determined by using annual counting of hydrogen isotopes (δD) and Na + seasonal cycles (Tsushima, 2015;Tsushima et al., 2015).These ice core samples were shaved off (~5 -10 mm) on a clean bench at -15°C in a cold room.A ceramic knife was used to avoid a possible adsorbed contamination during sample collection using the method previously reported (Kawamura et al., 2012;Pokhrel et al., 2015).These scraped samples were kept for 24 hours in a container in a standard clean room and were transferred into 800 ml glass bottles.All steps are followed as reported previously prior to analyses (Pokhrel et al., 2015;Pokhrel, 2016 et al., 2001).Total number of ice core sections was 147 (50 cm long, one quarter cut); i.e., sampling frequency was ~40% of 180 m deep ice core.
These melt ice core samples (150 mL) were concentrated to almost dryness using a rotary evaporator under a vacuum in a pear shape flask (300 ml) and extracted by a mixture of CH 2 Cl 2 /CH 3 OH (2:1) using an ultrasonic bath (Kawamura et al., 2012).The total dissolved and particulate organic matter was further eluted with CH 2 Cl 2 and methanol to extract the organic compounds adsorbed on the particles as reported previously (Fu et al., 2008;Simoneit et al., 2004).The extract and eluents were transferred to 1.5 mL glass vials and again dried under a nitrogen stream.
We conducted triplicate analyses for three real ice core samples to check the uncertainity in the determinations of concentrations.The uncertainity (standard deviation) of levoglucosan, dehydroabietic and vanillic acid were 6.72, 0.74 and 2.40 %, respectively.Moreover, recovery of traject compounds were better than 85%.
To identify the physical functioning fire smoldering spot as possible source

Results and Discussion
Anhydromonosaccharides can lead an important fraction of water-soluble organic carbon (Gao et al., 2015;Verma et al., 2015).It is produced from the pyrolysis and/or combustion of cellulose and/or hemi-cellulose from wildfires and domestic wood fires (Simoneit, 2002) at temperatures above 300 °C (Simoneit et al., 2002;Fraser and Lakshmanan, 2000;Shafizadeh, 1984).Many studies have shown that levoglucosan (C 6 H 10 O 5 ) is the most abundant anhydrous monosaccharide (Simoneit, 2002;Kuo et al., 2011;Hoffmann et al., 2010;Engling et al., 2006;) (Jordan et al., 2006;Simoneit et al., 1999) in the source regions of southern Alaska because the saddle of the Aurora Peak is far from the biomass burning source regions, as shown in Figure 1.

Levoglucosan
This study showed that concentrations of levoglucosan are 8.  et al., 2011;Hoffmann et al., 2010).However, we did not detect these isomer compounds at a significant concentration (ranges: BDL-0.0) in this study.Thus, levoglucosan/mannosan mass ratios (L/M) could be relatively high.In contrast many aerosol samples showed significant concentrations of these isomers and levoglucosan are reported in many aerosol samples collected from the oceans via "round-the-world cruise" (Fu et al., 2011), Mt.Tai in the North China Plain (Fu et al., 2008), and urban tropical India (Fu et al., 2010).
It should be noted that higher ratios of levoglucosan (L) to mannosan (M) indicated a sifnificant contributions of deciduous forest fire activities (Kawamura et al., 2012).For example, Kawamura et al. (2012) reported very low ratios of L/M (range: 3.3 -5.0) for an ice core of the Kamchatka Peninsula in Northeast Asia compared to lignite burning (30-90) at 200 C (Kuo et al., 2011), and aerosols samples of Gosan site in south Korea (15-40, ave.21) (Simoneit et al., 2004), suggesting gymnosperm sources for anhydrosugars (Kawamura et al., 2012).Hence, we cannot discuss more about the contributions of deciduous forest fire activities for our ice core from the source regions of southern Alaska.
Insignificant concentrations of mannosan and galactosan in our ice core indicate that combustion of lignite in the source regions of southern Alaska was minor.
These results suggest that contribution of lignite burning from East Asia, Eastern Russia, Siberia, higher latitudes of Alaskan regions, Japan, and Canadian regions to the ice core site was not significant.In contrast, western North Pacific ice core records from the Kamchatka Peninsula (Kawamura et al., 2012) showed these anhydrosugars.
This suggests that western and eastern North Pacific regions could be influenced by different air mass chemistry (e.g.lignite burning plume did not influence the southern It should be noted that degradation fluxes of levoglucosan in cloud droplets and aqueous particles (deliquescent particles) by OH radicals have been reported recently.For example, mean degradation fluxes were around 7.2 ng m −3 h −1 in summer and 4.7 ng m −3 h −1 in winter (Hoffmann et al., 2010).Hence, we can speculate that levoglucosan could be more stable compared to isomer compounds , whose degradation fluxes are lower than 7.2 and/or 4.7 ng m −3 h −1 (e.g., Fraser and Lakshmanan, 2000;Hoffmann et al., 2010) during long-range atmospheric transport from source points to southern Alaska.Stability of levoglucosan is further confirmed in an aerosol chamber study with atmospheric lifetime of 0.7-2.2days in summer (Hennigan et al., 2010).These results demonstrate the biomass burning emissions in source apportionment for the saddle of the APA.
Levoglucosan showed higher concentrations in around 1660s-1830s (Figure 2a) with sporadic peaks in 1678 (ice core depth in meter:  , 1913, 1966 and 2005) compared to before 1830s.This could be attributed to intensive grazing, agriculture and forest fire management (Marlon et al., 2008;Eichler et al., 2011).It should be noted that charcoal signals are scarce for Siberian regions compared to Northern American and European ice core records (Eichler et al., 2011).We did not detect significant conentrations of any isomers as we have discussed above.Moreover, two thirds of Earth's borel forest (17 million km 2 ) lies in Russia, which is a potential source of forest fires that could have significance on a global scale (Eichler et al., 2011;Isaev et al., 2002).
Mt. Logan Canada, GISP2, and 20D (older than 1850s) ice core records of Greenland are characterized by higher spikes of NH 4 + superimposed with a relatively uniform summertime and wintertime minimum (Whitlow et al., 1994).These suggest that ice core NH 4 + has common sources in the circumpolar regions.We got higher spikes of levoglucosan before 1840s (Figure 2a), which is consistent with higher spikes of NH 4 + in 1770-1790 and 1810-1830 in the Mt.Logan data (e.g., Whitlow et al., 1994).This comparison suggests similar source regions of NH 4 + for different sampling sites.In contrast, Mt.Logan data showed higher spikes of NH 4 + in the intervals of 1850-1870 and 1930-1980, which is dissimilar (except for two points) to our results from Aurora Peak (Figure 2a).It should be noted that Greenland records (GISP2 and 20D) showed lower spikes of NH 4 + compared to Mt. Logan (Whitlow et al., 1994) during these intervals (1850-1870 and 1930-1980), which is consistent to the results of Aurora Peak (except for 1966), again suggesting similar source regions (Whitlow et al., 1994;Davidson et al., 1993;Holdsworth et al., 1992).The potential source regions for Greenland ice cores include northern North America, Europe and Siberia.Simialry, Siberia, Alaska and British Columbia are likely source regions for Mt.Logan (Whitlow et al., 1994;Davidson et al., 1993;Holdsworth et al., 1992).
Except for a few points, e. Asia, and other human activities in the NH (Eichler et al., 2011;Robock, 1991;Achard et al., 2008;Balzter et al., 2007;Wallenius et al., 2005).Eichler et al. (2009) further confirmed that from 1816 to 2001 higher amounts of NH 4 + and formate (HCOO -) were directly emitted from biogenic sources rather than biomass burning (Olivier et al., 2006) in the Belukha glacier in the Siberian Altai mountains.Similarly, lower concentrations of charcoal between 1700 and 2000 in this Altai mountain further suggest that forest fire activities were stronger than anthropogenic activities in the source regions (Eichler et al., 2011).
Similarly, the sparsity of NH 4 + spikes after 1920 in Greenland (GISP2 and 20D) suggest low intensity of biomass burning and/or significant deposition before reaching Greenland from North America (Whitlow et al., 1994).This is similar to the saddle of Aurora Peak, except for 1910 (20800 ng/L), which may be due to a point , NO 3 -, NH 4 + showed significant concentrations during same periods) could be significantly deposited by short range atmospheric circulation on the exposed surface area of the glaciers.These special events further suggest that Alaskan glaciers can not preserve most biomass burning events in the circumpolar regions, which occured in the source regions of Siberian and North America.
Hence, these historical records of levoglucosan before the 1830s suggest long range atmospheric transport rather than short range transport from heavy forest fires.
For instance, forest fire intensity in 1660s-1830s could be induced by lightning during drought seasons in the Siberian regions as well as extensive burning to clear land for agriculture purposes in the NH (Whitlow et al., 1994 and reference therein).Declined concentrations of levoglucosan trend after the 1830s (except for few points), showing that sources could be changed significantly and/or forest fire activities could be suppressed and/or controlled in 1830s-1980s (Whitlow et al., 1994).It should be noted that mid to late 1800s are considered as the Little Ice Age (Mayewski et al., 1993).Moreover, recent changes of the concentration trends in the Alaskan source regions is thought to be climate driven (Whitlow et al., 1994 and reference therein).
These periods are consistent with those of higher spikes of levoglucosan, except for a few points (e.g., 1734-1738) before 1990 (Figure 2a, b).The historical trend of dehydroabietic acid concentrations is also similar to that of levoglucosan concentrations before 1980, which is similar to Kamchatka ice core records.In contrast, Kamchatka showed gradual increase of dehydroabietic acid (Figure 2b) after the 1950s (e.g., Kawamura et al., 2012).These results suggest that biomass burning plumes of pine, larch, spruce and fir trees in Siberian regions (Kawamura et al., 2012;Ivanova et al., 2010) could not reach southern Alaska significantly compared to Kamchatka, south eastern Russia.
Dehydroabietic acid concentrations after the 1980s were higher than levoglucosan, which is similar to Kamchatka records.This further suggests that biomass burning plumes from Siberian borel conifer trees could be transported to the North Pacific regions (Kawamura et al., 2012).It also suggests that East Asian regions (broad-leaf trees are common) could be important for levoglucosan rather than dehydroabietic acid (boreal forest fires in Siberia, i.e., pine trees).It should be noted that Alaska can receive different air masses from East Asia, Eastern Russia, Siberia, higher latitudes of Alaskan regions, Japan, and Canadian regions in the troposphere (>300 hPa) (Yasunari and Yamazaki, 2009) and Kamchatka-Peninsula also can receive air masses from Siberia, Far East, North China and Eastern Europe (Kawamura et al., 2012).
These results showed some similarity between levoglucosan records of Kamchatka and Alaska (except for few points) and some discrepancy between dehydroabietic acid records between these sampling sites.Kamchatka showed gradual increase after the 1950s.Alaska showed this after the 1980s, suggesting that coniferburning plumes could be transported significantly to Kamchatka, but not southern Alaska, in the 1950s -1980s.There is another possibility for this particular discrepancy of Kamchatka and Alaska: dehydroabietic acids could be decomposed during long-range transport (Kawamura et al., 2012;Simoneit and Elias, 2001)
In other words, dehydroabietic acids and p-hydroxybenzoic acid (p-HBA) could be more unstable compared to photo-degradation of levoglucosan during long range transport.For instance, higher sensitivity of dehydroabietic acid was reported compared to levoglucosan (Simoneit et al., 2002;Simoneit and Elias, 2001).It should be noted that we did not detect p-HBA from the same ice-core sample, which can be produced from incomplete combustion of grasses (Kawamura et al., 2012;Simoneit et al., 2002).In constrast, we detected significant amounts of dehydroabietic acid from 1665-2007 (Figure 2b).Hence, we may speculate that p-HBA could be more unstable compared to levoglucosan, dehydroabietic acid, and vanillic acid.

Comparison with ammonium, nitrite, nitrate and SO 4 2-
There are many studies of organic compounds and major inorganic ions of biomass burning for aerosol samples in the NH, which are reported elsewhere  (Kunwar et al., 2016;Zhu et al., 2015;Cong et al., 2015;Kunwar and Kawamura, 2014;Lazaar et al., 2011;Kundu et al., 2010;Wang et al., 2009).In addition, terephthalic acid could be a special tracer of plastic waste burning (Kawamura and Pavuluri, 2010;Pavuluri et al., 2010;Kunwar and Kawamura, 2014b) ) were used to better understand the atmospheric signal of biomass burning and/or the Pioneer Agriculture Revolution (PIA-GREV) in the NH.These results are reported elsewere (Holdsworth et al., 1996, Legrand andMayewski, 1997).For instance, a signal of biomass burning is ammonium (e.g., ([NH 4 ] 2 SO 4 ) in snow particles, which is a constitute of forest fire smoke (Holdsworth et al., 1996;Tsai et al.,2013 and references therein).
g., 1999 (436 ng/L) and 2005 (598 ng/L)), concentrations of levoglucosan drastically decreased in 1980-2008.This infers that forest fire activities could be controlled by many factors.For instance, Central and East Siberian forest fire activities were controlled by strong climate periodicity, e.g., Arctic Oscillation (AO), El Nino, intensification of the hydrological cycle in central Atmos.Chem.Phys.Discuss., https://doi.org/10.5194/acp-2019-139Manuscript under review for journal Atmos.Chem.Phys.Discussion started: 6 March 2019 c Author(s) 2019.CC BY 4.0 License.source around Alaskan region.Higher spikes of NH 4 + at Mt. Logan during 1900-1990 are likely originated from central and eastern Siberia (Robock, 1991), which is dissimilar to the source regions in this study.Only the exception is 1966 (2000 ng/L), suggesting that local biomass burning is also important in southern Alaska.Above results and discussions suggest the subsequent evidences: (a) heavy biomass burning could be activated in the source regions; (b) short range air mass circulation could quickly reach souhtern Alaska, causing higher concentration of levoglucosan; (c) dilution and/or scavenging of biomass plume enroute could be maximized after 1830s; (d) a common NH summertime biomass burning plume (e.g., same ice core records of SO 4 2- Atmos.Chem.Phys.Discuss., https://doi.org/10.5194/acp-2019-139Manuscript under review for journal Atmos.Chem.Phys.Discussion started: 6 March 2019 c Author(s) 2019.CC BY 4.0 License.
from Siberia before reaching southern Alaska (i.e.eastern North Pacific ice core) but not before reaching Kamchatka (i.e.western North Pacific).The Kamchatka ice core also doesn't show high spikes (except 1970) in the 1950s-1970s compared to before and after those decades.Moreover, a correlation of levoglucosan with dehydroabietic acid from 1665-1918 (R = 0.74) is better than from1918-1977 (0.13) and 1977-2007    (0.36).These relations are weaker (0.39, 0.04, and 0.22, respectively) for vanillic acid, except for 1913 and 1966 at all cases.The representing figures are shown in Figure 3a-c.Such types of lower spikes and/or sporadic peaks of levoglucosan and Atmos.Chem.Phys.Discuss., https://doi.org/10.5194/acp-2019-139Manuscript under review for journal Atmos.Chem.Phys.Discussion started: 6 March 2019 c Author(s) 2019.CC BY 4.0 License.dehydroabietic acid after the 1920s (Figure 2a,b) and these correlations suggest that source regions should be different (e.g.east Asian broad leaf trees and Siberian source, e.g.boreal forest/pine trees), and long range atmospheric transport is insignificant for these historical concentration trends of dehydroabietic acid rather than levoglucosan over the saddle of Aurora Peak at least after the 1920s.Annual composite maps (Figure 5a-f) since 2001 to 2008 of the Moderate Resolution Imaging Spectroradiometer (MODIS) supported our above results and discussion.For example,levoglucosan (in 2005, 2006and 2004 AD with 598.0, 130.8, and 95.30ng/L,    respectively), dehydroabetic acid (in 2007, 2004, and 2006 AD with 555.9, 309.7, and    298.1ng/L, resppectively) and vanillic acid (in 2005, 2007 and 2006 with 18.57, 12.66,    and 7.27ng/L) showed descripency of higher spikes in the same years (Figure5a-f) suggested that they have different sources in the same years.

Figure 1 .
Figure 1.Geographical location of Aurora Peak in Alaska, where 180-meter long ice 634 core was drilled on the saddle of this peak in 2008 16(Pokhrel, 2015).635

Figure 2 .
Figure 2. Concentration changes of (a) levoglucosan, (b) dehydroabietic, and (c) vanillic acids in the ice core collected from Aurora Peak in Alaska for 1665-2008.

Figure 3 .
Figure 3. Correlations between the concentrations of (a) dehydroabietic and vanillic (b) vanillic and levoglucosan, and (c) levoglucosan and dehydroabietic acid in the Alaska ice core records collected from the saddle of Aurora Peak after the Great Pacific Climate Shift (1977-2007).
is completely different with this study.Hence, this study revels a new dimension of biomass burning periodic cycles in the NPR, which can alter the concept of other ice core studies in the NH.