Silicon limitation and replenishment in central Arctic Chukchi Sea Shelf region during ice melting period

doi:10.13745/j.esf.sf.2022.1.17

Abstract

Abstract:

The relatively nitrogen-deprived (16>N:P≈7) nutrients carried by Pacific water inflow provide important support to the upper Arctic Ocean ecosystem. In the Chukchi Sea Shelf region nutrient consumption is strong as sea ice retreats and light becomes more accessible. It is generally believed that the primary production of this region is mainly limited by nitrogen, while little is known about other nutrients including silicate. In this study, based on the results of two simultaneous voyages—the 2016 Chinese Arctic Research Expedition and the 2016 Chinese-Russian “Arctic Silk Road” Expedition—we revealed the distribution pattern of nutrients in the entire shelf region during ice melting period. The nitrite and nitrate surface layers are nearly exhausted over a wide area, while silicate is low in the shelf center and high in the surrounding areas, indicating silicon and nitrogen are both limited at the shelf center. Along the path of Pacific water inflow, silicate concentrations are higher at depths above 30 m at stations S01, R01 and LV77-01 than at the end of water inflow, indicating silicate is released to the bottom water from sediment pore water. Therefore, sediment pore water can be potential source of silicate for the upper ocean in shallow shelf areas. In this study, combined with literature data, the calculated average silicate flux at the shelf sediment-water interface was 630.78 mmol·m^-2·a^-1, or 3.75×10¹¹ mol·a^-1 in total silicate, which equaled to half of silicate carried by Pacific water inflow (6.59×10¹¹ mol·a^-1). Thus sediment pore water is also an important source of silicate in the Chukchi Sea Shelf region.

Key words: Arctic Ocean, Chukchi Sea Shelf, silicate, silicon limitation

CLC Number:

P736.4

LIU Jie, LI Zhongqiao, ZHANG Anyu, REN Jian, BAI Youcheng, ZHUANG Yanpei, LI Yangjie, LI Hongliang, JIN Haiyan, CHEN Jianfang. Silicon limitation and replenishment in central Arctic Chukchi Sea Shelf region during ice melting period[J]. Earth Science Frontiers, 2022, 29(4): 103-112.

Figures/Tables 12

Fig.1 Map of the Chukchi Sea Shelf region showing the locations of research stations for the 2016 Chinese Arctic Research Expedition (red dots) and 2016 Chinese-Russian Joint Expedition (blue dots) and sampling stations for sediment-overlying water (yellow dots) and pore water (green dots), and ocean currents (modified after [18-19]) in the study area.

Fig.2 (a) Surface salinity distribution map of the study area and (b) salinity profile of NB section in the south of the Bering Strait

Fig.3 Potential temperature-salinity-depth plots for Chukchi Sea. Blue line represents 30.5 psu salinity. Green line represents 31.5 psu salinity.

Fig.4 Silicate distributions in surface water (a), at 10 m (b) and 25 m (c) depths, and in bottom water (d)

Fig.5 Nitrate and nitrite distributions in surface (a) and bottom (b) water

Fig.6 Section of AW (a) and silicate distribution in the section (b)

Fig.7 Variations of silicate concentrations with depth in sediment-overlying water (top panel) and pore water (bottom panel) at stations LV77-02 (left panel) and LV77-04 (right panel)

Fig.8 N:P:Si scatter plots to assess potential nutrient limitations of the study area.

Table 1 Nutrient parameters for Pacific water influx in summer

水流	温度/℃	盐度/psu	浓度/(μmol·L^-1)
水流	温度/℃	盐度/psu	硅酸盐	磷酸盐	硝酸盐和亚硝酸盐	铵盐
ACW	9.42±0.93	28.65±0.40	20.03±1.52	0.85±0.05	0.47±0.22	0.42±0.34
BSW	6.88±0.43	31.02±0.09	16.37±2.58	0.96±0.09	0.93±0.65	0.82±0.40
AW	4.18±1.84	31.94±0.24	20.03±10.85	1.29±0.47	6.33±2.86	1.27±0.94

Fig.9 The relative potential limitation of nutrients based on historical data and all data in this study (data from 2010, 2012,2014,2016 Chinese Arctic Research Expedition and 2016 Chinese-Russian “Arctic Silk Way”). Adapted from [42,44]

Table 2 Silicate flux at the sediment-water interface in the Chukchi Sea

站位	Ф	D_sed/(10^-10m²·s^-1)	dC/dx/(mol·m⁴)	J_sed/(mmol·m^-2·a^-1)
LV77-02	0.62	3.57	71.48	499.67
LV77-04	0.62	3.57	62.86	439.37

Table 3 Silicate fluxes at sediment-water interface on the western Arctic Ocean shelf

海域	水深/m	站位	经度E/(°)	纬度N/(°)	J_sed/(mmol·m^-2·a^-1)	参考文献
楚科奇海	50	CC1	-168.96	67.67	1 131.87	文献[31]
	52	R06	-168.98	69.5	605.90
	51	C07	-165.33	72.54	477.06
波弗特海	47	MD-C	-133.57	70.19	1 090.12	文献[46]
	55	MD-W	-137.94	69.49	411.28
	60	MD-E	-130.61	71.27	627.85

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