Wave climate and extremes on a mesotidal atoll lagoon

Costa, Mirella B.; Siegle, Eduardo

doi:10.1590/2675-2824070.22033mbc

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Ocean and Coastal Research

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Original Article • Ocean Coast. Res. 70 • 2022 • https://doi.org/10.1590/2675-2824070.22033mbc copy

Wave climate and extremes on a mesotidal atoll lagoon

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

Processes on atolls and coral reef lagoons are defined by local wave and tide climates. Based on the reconstruction of lagoon wave climate by downscaling offshore historical wave information, this study aims to assess the wave climate and wave extremes on a mesotidal atoll lagoon (Rocas Atoll, Brazil). Results show that the transformation of offshore waves, when propagating into the lagoon, results in a different and far more homogeneous wave climate. Atoll morphology and tides play a key role in controlling the directional and energy characteristics of the lagoon wave climate. Refraction processes and the reef passage make the side protected from the dominant SE waves the most energetic zone for lagoon wave propagation. Lagoon waves tend to propagate in opposite directions to offshore wind waves, showing the refraction effect of approaching waves when crossing the atoll rim and the channel. The tidal effect on the dissipation process is also a filter for extreme wave conditions. We highlight the dependence of the resulting lagoon wave climate on atoll morphology, thereby addressing its implications to geomorphological process inside the atoll.

Descriptors:
Wave propagation; Reef wave transformation; Rocas Atoll

Intensity	Wave Power (kW/m)
Extreme	P ≥ 50
Severe	50 > P ≥ 40
Strong	40 > P ≥ 30
Moderate	30 > P ≥ 20
Weak	20 > P ≥ 10
Calm	P < 10

Pattern	Class	Significant wave height		Peak wave period
Pattern	Class	Range (m)	Percentual (%)	Range (s)	Percentual (%)
Offshore
Typical	Modal class	2,0 - 2,5	49,2	8,0 - 10,0	31,4
Extreme	Percentil 99%	3,04 - 3,93	1	17,2 - 21,8	1
Lagoon
Typical	Modal class	0,0 - 0,5	98,6	4,0 - 6,0	47,9
Extreme	Percentil 99%	0,52 - 0,81	1	9,7 - 13,3	1

Offshore
Maximum annual Hs						Maximum annual Tp
Year	Month	Hs (m)	Tp (s)^*	D^*	Tide (m)	Year	Month	Tp (s)	Hs (m)^*	D^*	Tide (m)
1980	8	3.45	8.35	S	1.53	1980	2	20.26	1.7	N	1.66
1981	5	3.43	12.27	S	0.36	1981	3	20.35	2.34	S	2.1
1982	2	3.93	16.19	N	1.12	1982	4	20.33	1.99	S	1.64
1983	12	3.47	17.81	N	1.94	1983	12	19.84	2.04	N	1.25
1984	11	3.09	15.61	S	1.37	1984	8	20.42	1.99	S	1.47
1985	2	3.5	15.72	N	1.44	1985	2	21.21	1.68	N	0.38
1986	6	3.24	8.98	S	1.85	1986	12	19.06	1.85	S	1.9
1987	12	2.9	15.22	N	1.98	1987	2	21.79	2.28	N	1.62
1988	7	3.49	9.64	S	0.99	1988	11	20.58	2.15	N	0.53
1989	5	3.06	12.36	S	1.46	1989	6	20.06	1.75	S	2.3
1990	6	3.05	8.83	S	0.6	1990	11	19.74	2.19	N	1.75
1991	8	3.75	9.84	S	2.12	1991	1	19.63	2.78	N	0.4
1992	9	3.19	9.86	S	1.35	1992	9	18.5	1.91	S	1.82
1993	7	3.1	8.36	S	0.23	1993	3	18.97	2.25	N	0.58
1994	7	2.97	15.47	S	1.25	1994	12	19.11	1.59	N	0.6
1995	7	3.34	10.21	S	2.05	1995	8	18.83	2.24	S	0.27
1996	9	3.86	11.45	S	0.45	1996	1	20.03	2.27	N	1.78
1997	8	3.07	8.84	S	0.09	1997	12	21.03	1.39	N	0.2
1998	8	3.03	10.55	S	2.03	1998	11	20.37	1.83	S	1.54
1999	8	3.59	15.38	S	0.9	1999	1	20.94	1.97	N	2.16
2000	9	3.27	11.72	S	0.49	2000	12	19.11	2.02	N	1.85
2001	8	3.15	12.79	S	2.03	2001	2	18.5	2.58	N	-0.01
2002	8	3.7	10.93	S	0.59	2002	3	20.72	1.77	S	1.3
2003	7	3.02	9.76	S	2.01	2003	11	21.23	1.9	N	1.78
2004	8	3.31	11.07	S	1.56	2004	8	19.02	2.17	S	2.04
2005	7	3.2	13.52	S	1.25	2005	10	19.95	2.01	N	0.28
2006	7	3.63	9.83	S	1.8	2006	3	18.55	1.66	N	-0.01
2007	8	3.54	10.27	S	0.45	2007	1	19.31	1.5	N	1.72
2008	8	3.57	11.31	S	1.45	2008	9	18.77	2.44	S	1.08
2009	12	3.19	16.59	N	0.63	2009	5	19.82	1.52	S	2.28
2010	9	3.51	10.28	S	0.4	2010	2	19.62	1.79	N	2.36
2011	8	3.66	15.56	S	2.1	2011	5	17.82	2.16	S	1.8
2012	8	3.54	10.35	S	1.46	2012	7	19.27	2.18	S	2.15
2013	8	3.41	16.96	S	0.44	2013	12	20.29	2.31	N	1.82
2014	5	3.37	17.6	S	1.75	2014	8	20.14	2.25	S	2.13

Lagoon
Maximum annual Hs						Maximum annual Tp
Year	Month	Hs (m)	*Tp (s)^ * Associated values to Hs and Tp.**	*D^ * Associated values to Hs and Tp.**	Tide (m)	Year	Month	Tp (s)	*Hs (m)^ * Associated values to Hs and Tp.**	*D^ * Associated values to Hs and Tp.**	Tide (m)
1980	9	0.73	8.10	N	2.73	1980	2	12.39	0.31	N	1.66
1981	3	0.81	11.84	S	2.65	1981	2	12.32	0.59	S	2.22
1982	2	0.75	9.89	S	2.57	1982	4	12.16	0.12	N	1.04
1983	1	0.68	7.51	N	2.65	1983	12	12.13	0.22	N	1.25
1984	10	0.66	7.56	S	2.60	1984	12	12.03	0.19	N	1.07
1985	2	0.73	12.20	N	2.54	1985	7	12.47	0.13	N	1.13
1986	11	0.62	8.56	S	2.46	1986	3	11.46	0.25	N	1.38
1987	2	0.79	11.12	S	2.65	1987	2	13.32	0.34	N	1.62
1988	2	0.78	9.76	N	2.76	1988	11	12.06	0.28	N	1.46
1989	3	0.72	9.06	N	2.71	1989	9	11.65	0.14	N	1.22
1990	2	0.72	10.54	S	2.58	1990	11	11.90	0.36	N	1.75
1991	1	0.77	11.32	S	2.59	1991	1	11.84	0.20	N	1.24
1992	1	0.75	10.72	S	2.68	1992	4	10.96	0.33	N	1.69
1993	10	0.68	7.68	N	2.62	1993	9	11.14	0.20	N	1.25
1994	2	0.76	10.03	S	2.65	1994	12	11.55	0.23	N	1.41
1995	1	0.74	10.61	N	2.64	1995	3	11.03	0.20	N	1.20
1996	1	0.72	9.60	N	2.67	1996	1	12.17	0.39	N	1.78
1997	3	0.70	7.44	N	2.72	1997	12	12.26	0.16	N	1.00
1998	3	0.70	7.47	N	2.70	1998	11	12.29	0.12	N	1.07
1999	10	0.80	11.94	N	2.63	1999	1	12.87	0.55	S	2.16
2000	1	0.68	7.86	S	2.61	2000	12	11.60	0.39	N	1.85
2001	2	0.81	11.50	N	2.70	2001	2	11.50	0.81	N	2.70
2002	10	0.73	8.72	N	2.71	2002	3	12.18	0.14	N	1.30
2003	4	0.74	9.41	N	2.67	2003	11	12.89	0.37	N	1.78
2004	1	0.70	9.07	S	2.58	2004	1	11.17	0.25	N	1.40
2005	10	0.72	10.76	S	2.54	2005	10	11.87	0.24	N	1.36
2006	3	0.77	10.71	N	2.71	2006	3	10.75	0.18	N	1.14
2007	2	0.74	9.48	N	2.70	2007	1	11.82	0.21	N	1.34
2008	1	0.65	8.60	S	2.56	2008	9	11.10	0.13	N	1.08
2009	2	0.72	8.61	N	2.66	2009	5	11.60	0.11	N	1.16
2010	1	0.72	7.30	S	2.74	2010	2	11.99	0.60	S	2.36
2011	2	0.73	8.55	N	2.74	2011	1	10.74	0.22	N	1.33
2012	2	0.68	9.88	S	2.56	2012	1	10.78	0.21	N	1.34
2013	3	0.69	9.95	S	2.51	2013	12	12.34	0.48	N	2.01
2014	1	0.70	7.52	N	2.71	2014	1	11.51	0.68	N	2.53

Return period (years)	Offshore			Lagoon
Return period (years)	Hs (m)	Tp (s)	P (kW/m)	Hs (m)	Tp (s)	P (kW/m)
2	3.32	19.66	89.63	0.72	11.73	2.87
5	3.56	20.64	106.88	0.77	12.38	3.52
10	3.75	21.29	118.31	0.80	12.81	3.95
25	3.97	22.1	132.74	0.85	13.36	4.49
50	4.13	22.71	147.44	0.88	13.76	4.89
100	4.29	23.31	154.07	0.91	14.12	5.23

1% of P (kW/m) maximum values
Offshore					Lagoon
Year	Month	P (kW/m)	Tide (m)	Direction	Year	Month	P (kW/m)	Tide (m)	Direction
1982	2	142.53	2.57	N	1981	3	4.46	2.65	NE
2011	8	127.65	2.13	S	2001	2	4.35	2.70	NE
1983	12	122.24	1.94	N	1999	10	4.32	2.63	NE
2013	8	115.22	2.10	S	1987	2	3.94	2.65	NE
2014	5	113.93	2.31	S	1991	1	3.80	2.59	NE
1999	8	112.98	2.31	S	1985	2	3.67	2.54	NE
1985	2	112.12	2.54	NO	2006	3	3.58	2.71	NE
1999	1	106.06	2.52	N	2005	10	3.44	2.51	NE
2007	8	102.74	2.31	SE	1992	1	3.44	2.68	NE
1985	12	102.35	1.91	N	1999	1	3.43	2.52	NE
1996	8	102.16	1.97	S	1988	2	3.43	2.76	NE
1981	5	99.11	2.14	S	1995	1	3.35	2.64	NE
1981	3	98.01	2.65	NO	1994	2	3.33	2.65	NE
1996	9	97.24	1.81	SE	1982	2	3.18	2.57	NE
2009	12	96.23	2.04	N	1990	2	3.12	2.58	NE

Instituto Oceanográfico da Universidade de São Paulo Praça do Oceanográfico 191, CEP: 05508-120, São Paulo, SP - Brasil, Tel.: (11) 3091-6501 - São Paulo - SP - Brazil
E-mail: diretoria.io@usp.br

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[1] *Corresponding author: mirella.costa@ufpe.br