Space–time dynamics of carbon and environmental parameters related to carbon dioxide emissions in the Buor-Khaya Bay and adjacent part of the Laptev Sea

Abstract

This study aims to improve understanding of carbon cycling in the Buor-Khaya Bay (BKB) and adjacent part of the Laptev Sea by studying the inter-annual, seasonal, and meso-scale variability of carbon and related hydrological and biogeochemical parameters in the water, as well as factors controlling carbon dioxide (CO₂) emission. Here we present data sets obtained on summer cruises and winter expeditions during 12 yr of investigation. Based on data analysis, we suggest that in the heterotrophic BKB area, input of terrestrially borne organic carbon (OC) varies seasonally and inter-annually and is largely determined by rates of coastal erosion and river discharge. Two different BKB sedimentation regimes were revealed: Type 1 (erosion accumulation) and Type 2 (accumulation). A Type 1 sedimentation regime occurs more often and is believed to be the quantitatively most important mechanism for suspended particular matter (SPM) and particulate organic carbon (POC) delivery to the BKB. The mean SPM concentration observed in the BKB under a Type 1 regime was one order of magnitude greater than the mean concentration of SPM (~ 20 mg L⁻¹) observed along the Lena River stream in summer 2003. Loadings of the BKB water column with particulate material vary by more than a factor of two between the two regimes. Higher partial pressure of CO₂ (<i>p</i>CO₂), higher concentrations of nutrients, and lower levels of oxygen saturation were observed in the bottom water near the eroded coasts, implying that coastal erosion and subsequent oxidation of eroded organic matter (OM) rather than the Lena River serves as the predominant source of nutrients to the BKB. Atmospheric CO₂ fluxes from the sea surface in the BKB vary from 1 to 95 mmol m⁻² day⁻¹ and are determined by specific features of hydrology and wind conditions, which change spatially, seasonally, and inter-annually. Mean values of CO₂ emission from the shallow Laptev Sea were similar in September 1999 and 2005 (7.2 and 7.8 mmol m⁻² day⁻¹, respectively), while the CO₂ efflux can be one order lower after a strong storm such as in September 2011. Atmospheric CO₂ emissions from a thawed coastal ice complex in the BKB area varied from 9 to 439 mmol m⁻² day⁻¹, with the mean value ranged from 75.7 to 101 mmol m⁻² day⁻¹ in two years (September 2006 and 2009), suggesting that at the time of observations the eroded coastal area served as a more significant source of CO₂ to the atmosphere than the tundra (mean value: 22.7 mmol m⁻² day⁻¹) on the neighboring Primorsky coastal plain (September 2006). The observed increase in the Lena River discharge since the 1990s suggests that increased levels of "satellite-derived" annual primary production could be explained by an increasing load of humic acids delivered to shelf water; in this water the color resulting from the presence of CDOM (colo...

The spatial and interannual dynamics of the surface water carbonate system and air–sea CO&lt;sub&gt;2&lt;/sub&gt; fluxes in the outer shelf and slope of the Eurasian Arctic Ocean

“…4). Supersaturation was observed in the southern Laptev Sea outside the Lena River delta, which is typical in surface waters of the eastern Laptev Sea inner and middle shelves (Anderson et al, 2009;Semiletov et al, 2012Semiletov et al, , 2013Pipko et al, 2016). Moreover, high pCO 2 was also observed in the surface waters of the outer Laptev Sea shelf over the Lomonosov Ridge and further to the east (Fig.…”

“…The higher CO 2 content of river runoff in 2007 not only contributed to high pCO 2 but also enhanced surface water temperature due to its high concentration of CDOM, which adsorbs solar radiation Semiletov et al, 2013). Except for the lower runoff content compared to 2007, the main con-I.…”

“…Together with limited nutrient content, these conditions make these seas unproductive, 5-10 times less productive than inflow shelves (Carmack et al, 2006). Moreover, intense inflow of terrigenous OM, low productivity, as well as sub-sea release of methane that partly oxidizes , make significant areas of these seas heterotrophic, where CO 2 outgassing to the atmosphere is observed (Anderson et al, 2009(Anderson et al, , 2011Pipko et al, 2005Pipko et al, , 2011aSemiletov et al, 2007Semiletov et al, , 2012Semiletov et al, , 2013.…”

“…Studies of the Barents Sea carbonate system (Årthun et al, 2012;Lauvset et al, 2013;Pipko et al, 2011b;Yakushev and Sørensen, 2013) as well as the ESAS waters (Anderson et al, 2009(Anderson et al, , 2011Pipko et al, 2011aPipko et al, , 2015Pipko et al, , 2016Semiletov et al, 2012Semiletov et al, , 2013Semiletov et al, , 2016 have been performed during the last decade. The Kara Sea remains less studied in the context of carbonate system dynamics and the main research was accomplished in the shallow part of this sea (Makkaveev et al, 2010(Makkaveev et al, , 2015.…”

Sonar gas flux estimation by bubble insonification: application to methane bubble flux from seep areas in the outer Laptev Sea

“…ESAS subsea permafrost degradation allows the release of sequestered CH 4 to the shallow ocean and atmosphere and has been changing in response to glacial and interglacial Arctic warming (∼ 7 • C) and warming from the overlying seawater (∼ 10 • C) since inundation in the early Holocene with additional ESAS seawater warming in recent decades (Biastoch et al, 2011;Semiletov et al, 2013Semiletov et al, , 2012Shakhova et al, 2014).…”