Composed structure of mesoscale eddy in the Northwest Pacific Ocean and its influence on acoustic propagation

doi:10.3969/j.issn.1001-909X.2024.01.006

Abstract

Abstract:

Mesoscale eddies widely exist in the ocean and affect the sound propagation. Using AVISO altimeter and Argo buoy data from 2000 to 2018, the multi-year average three-dimensional structure of mesoscale eddies in the Kuroshio and Oyashio extension regions in the Northwest Pacific Ocean was constructed by synthesis method, and the structural characteristics of temperature anomalies, salt anomalies and sound velocity were analyzed. The sound propagation in eddies is simulated by using Bellhop ray acoustic model. The results show that : (1) Under the background of the cold eddy, the temperature anomaly is negative, the salinity anomaly is negative in the upper layer and positive in the lower layer, and the sound velocity contour rises. Under the background of warm eddy, the temperature anomaly is positive, the salinity anomaly is positive in the upper layer and negative in the lower layer, and the sound velocity contour is sinking. (2) The cold eddies cause the convergence region to shift towards the sound source direction and the width of convergence zone to decrease; the warm eddies cause the convergence zone to move away from the sound source and increase its width. The convergence area in the Kuroshio extension region is wider than that in the Oyashio extension region, and is further away from the sound source. (3) The cold eddies make the convergence zone turning depth shallower, while the warm eddies make the convergence zone turning depth deeper. In the Kuroshio extension region, the inversion depth is shallower with the increase of longitude,but in the Oyashio extension region, the inversion depth is deeper with the increase of longitude.

Key words: mesoscale eddy, Northwest Pacific Ocean, Argo buoy, sound propagation, convergence zone

CLC Number:

P733.21

ZHANG Xudong, QIU Zhongfeng, MAO Kefeng, WANG Penghao. Composed structure of mesoscale eddy in the Northwest Pacific Ocean and its influence on acoustic propagation[J]. Journal of Marine Sciences, 2024, 42(1): 58-68.

Figures/Tables 11

Fig.1 The study area and sea surface temperature distribution (Sea surface temperature data are from CARS09.)

Fig.2 The distribution of SLA and eddy in the Northwest Pacific Ocean (2015-10-18) (Figure b shows that Argo buoy is located outside the eddy; Figure c shows that Argo buoy is located inside the eddy; the closed curve represents the eddy boundary; red dot represents the center of the eddy; the black dot represents the Argo buoy location; the ΔxE represents the meridional distance from Argo buoy to the eddy center, and the ΔyE represents the zonal distance.)

Tab.1 Number of Argo profiles conforming to the matching conditions in 9 subregions of the Northwest Pacific Ocean

区域	子区域	Argo剖面资料数量
区域	子区域	与暖涡匹配/条	与冷涡匹配/条
区域Ⅰ 黑潮延伸体	A	736	494
	B	736	388
	C	376	354
	D	309	229
	E	287	259
区域Ⅱ 亲潮延伸体	F	280	413
	G	509	302
	H	267	222
	I	147	105

Fig.3 Mean temperature-salinity profile in 9 subregions of the Northwest Pacific Ocean (Black dotted lines represent the potential density σθ.)

Fig.4 Potential temperature anomaly distribution of the composed eddy in 9 subregions of the Northwest Pacific Ocean at ΔY=0 cross section

Fig.5 Salinity anomaly distribution of the composed eddy in 9 subregions of the Northwest Pacific Ocean at ΔY=0 cross section

Fig.6 Sound velocity profiles at the eddy center under without eddy, cold eddy and warm eddy background in the 9 subregions of the Northwest Pacific Ocean

Fig.7 Sound velocity contour of eddy center under warm eddy background (a) and cold eddy background (b) in subregion C of the Northwest Pacific Ocean

Fig.8 Acoustic propagation loss under the background of warm eddy, cold eddy and without eddy in 9 subregions of the Northwest Pacific Ocean

Tab.2 Location and width of convergence zone under the background of warm eddy, cold eddy and without eddy in 9 subregions of the Northwest Pacific Ocean

区域		环境背景	最大声速差 /dB	会聚区与声源的距离/km		会聚区宽度/km		反转深度/m
区域		环境背景	最大声速差 /dB	d₁	d₂	W₁	W₂	反转深度/m
区域I 黑潮延伸体	A	无涡旋		62.25	123.24	8.34	8.82	4 026
		冷涡	4.042	61.63	122.05	8.10	8.60	3 927
		暖涡	10.867	64.07	127.09	8.68	9.44	4 058
	B	无涡旋		62.05	122.80	8.12	8.52	3 885
		冷涡	9.539	60.60	119.83	7.84	7.98	3 831
		暖涡	7.958	63.52	125.78	8.37	8.98	3 961
	C	无涡旋		61.40	121.76	8.03	8.26	3 820
		冷涡	14.457	59.02	116.90	7.61	7.59	3 625
		暖涡	6.519	62.64	124.21	8.22	8.59	3 847
	D	无涡旋		61.05	121.03	7.55	8.03	3 809
		冷涡	6.957	59.87	118.38	7.35	7.60	3 670
		暖涡	3.254	61.48	121.95	7.66	8.45	3 831
	E	无涡旋		59.65	119.00	7.33	7.9	3 744
		冷涡	5.526	58.80	117.68	7.29	7.64	3 654
		暖涡	1.978	59.83	119.51	7.44	8.12	3 821
区域Ⅱ 亲潮延伸体	F	无涡旋		45.12	85.82	5.72	8.86	1 742
		冷涡	16.106
		暖涡	4.094	45.74	86.15	5.81	6.32	1 763
	G	无涡旋		50.22	92.56	6.65	7.10	2 189
		冷涡	10.023	42.24	85.54	5.42	5.62	1 948
		暖涡	3.222	45.93	93.92	6.84	7.40	2 229
	H	无涡旋		44.96	93.85	7.01	7.64	2 328
		冷涡	8.884	44.02	91.56	5.80	6.26	2 119
		暖涡	7.227	47.52	97.13	7.64	8.43	2 376
	I	无涡旋		48.40	99.55	7.17	7.74	2 461
		冷涡	7.563	45.97	97.16	6.07	6.31	2 167
		暖涡	2.048	48.75	100.94	7.34	8.12	2 480

Fig.9 Schematic diagram of turning depth

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