SOMLIT temperature data overview

1 Location of SOMLIT stations

The monitoring sites are grouped into their parent SOMLIT stations and ordered from north to south throughout this document.

SOMLIT stations and monitoring sites, ordered from north to south

SOMLIT station	Monitoring site(s)
Wimereux	Point L, Point C
Luc-sur-Mer	Smile, Luc-sur-Mer
Dinard	Le Buron, Cézembre
Roscoff	Estacade, Astan
Brest	Portzic, Lanvéoc
La Rochelle	Antioche
Gironde	pk86, pk52, pk30
Arcachon	Comprian, Eyrac, Bouée 13
Banyuls	Sola
Sète	Sète
Marseille	Frioul
Villefranche-sur-Mer	Point B

2 Temperature data

Only observations with a valid date, a non-missing in-situ temperature and a sampling level coded S (surface) or F (bottom) are retained. All observations assigned to a given level are pooled irrespective of numerical depth.

2.1 Data availability

Temperature data availability for surface and bottom sampling levels

Site	Station	Depth	Start date	End date	Time span (years)	Number of observations	Minimum depth (m)	Maximum depth (m)
Wimereux	Point L	Surface	1998-01-12	2026-06-15	28.4	327	1.0	1.0
		Bottom	1998-01-27	2026-06-15	28.4	320	50.0	50.0
	Point C	Surface	1998-01-12	2026-06-15	28.4	416	1.0	2.0
		Bottom	1998-01-27	2026-06-15	28.4	406	25.0	25.0
Luc-sur-Mer	Smile	Surface	2013-04-09	2026-02-02	12.8	260	2.0	2.0
	Luc-sur-Mer	Surface	2007-01-04	2026-02-02	19.1	420	2.0	2.0
Dinard	Le Buron	Surface	2011-12-15	2024-11-28	13.0	269	1.0	1.0
		Bottom	2011-12-15	2012-12-18	1.0	23	22.0	22.0
	Cézembre	Surface	2014-03-07	2023-12-18	9.8	205	1.0	1.0
Roscoff	Estacade	Surface	1997-01-03	2026-07-23	29.6	690	1.0	1.0
	Astan	Surface	2000-02-28	2026-07-23	26.4	632	1.0	1.0
		Bottom	2000-02-14	2026-07-23	26.4	631	60.0	60.0
Brest	Portzic	Surface	1998-03-25	2026-04-27	28.1	1367	2.0	2.0
	Lanvéoc	Surface	2019-01-08	2026-04-23	7.3	157	2.0	2.0
La Rochelle	Antioche	Surface	2011-06-22	2026-07-03	15.0	327	1.0	1.0
Gironde	pk86	Surface	1997-03-03	2026-03-26	29.1	509	1.0	1.0
		Bottom	1997-03-03	2026-03-26	29.1	509	7.0	13.0
	pk52	Surface	1997-01-21	2026-03-25	29.2	554	1.0	1.0
		Bottom	1997-01-21	2026-03-25	29.2	554	2.0	9.0
	pk30	Surface	1997-01-20	2026-03-27	29.2	554	1.0	1.0
		Bottom	1997-01-20	2026-03-27	29.2	554	4.0	10.0
Arcachon	Comprian	Surface	2005-01-21	2026-04-23	21.3	447	1.0	8.0
	Eyrac	Surface	1997-01-15	2026-04-23	29.3	757	1.0	7.3
		Bottom	1997-01-15	2004-09-17	7.7	302	6.0	6.0
	Bouée 13	Surface	2005-01-21	2026-04-23	21.3	451	1.0	22.0
Banyuls	Sola	Surface	1997-03-13	2026-04-30	29.1	1244	3.0	3.0
		Bottom	1997-03-13	2026-04-30	29.1	1220	24.0	24.0
Sète	Sète	Surface	2015-02-17	2025-12-17	10.8	224	1.0	2.0
Marseille	Frioul	Surface	1997-01-28	2026-05-26	29.3	680	1.0	1.0
		Bottom	2004-01-16	2026-05-26	22.4	499	1.0	55.0
Villefranche-sur-Mer	Point B	Surface	1997-01-02	2024-05-28	27.4	1332	1.0	2.0
		Bottom	1997-01-02	2024-05-28	27.4	1327	50.0	50.0

2.2 Data visualisation

2.2.1 Wimereux

2.2.2 Luc-sur-Mer

2.2.3 Dinard

2.2.4 Roscoff

2.2.5 Brest

2.2.6 La Rochelle

2.2.7 Gironde

2.2.8 Arcachon

2.2.9 Banyuls

2.2.10 Sète

2.2.11 Marseille

2.2.12 Villefranche-sur-Mer

2.3 Descriptive statistics

Descriptive statistics for in-situ temperature observations

Site	Station	Depth	Start date	End date	Time span (years)	N	Mean temperature (°C)	Median temperature (°C)	Minimum temperature (°C)	Maximum temperature (°C)
Wimereux	Point L	Surface	1998-01-12	2026-06-15	28.4	327	12.77	12.90	5.20	20.14
		Bottom	1998-01-27	2026-06-15	28.4	320	12.58	12.73	5.21	19.80
	Point C	Surface	1998-01-12	2026-06-15	28.4	416	12.66	12.44	4.93	20.80
		Bottom	1998-01-27	2026-06-15	28.4	406	12.50	12.27	4.92	20.30
Luc-sur-Mer	Smile	Surface	2013-04-09	2026-02-02	12.8	260	13.49	13.15	6.43	21.02
	Luc-sur-Mer	Surface	2007-01-04	2026-02-02	19.1	420	12.95	12.59	4.06	21.27
Dinard	Le Buron	Surface	2011-12-15	2024-11-28	13.0	269	12.69	12.53	0.00	20.49
		Bottom	2011-12-15	2012-12-18	1.0	23	12.89	12.01	8.22	18.90
	Cézembre	Surface	2014-03-07	2023-12-18	9.8	205	13.79	13.72	7.06	20.53
Roscoff	Estacade	Surface	1997-01-03	2026-07-23	29.6	690	13.13	13.21	7.60	17.50
	Astan	Surface	2000-02-28	2026-07-23	26.4	632	13.03	13.10	8.30	16.95
		Bottom	2000-02-14	2026-07-23	26.4	631	12.96	13.10	8.50	16.61
Brest	Portzic	Surface	1998-03-25	2026-04-27	28.1	1367	13.48	13.55	7.88	18.70
	Lanvéoc	Surface	2019-01-08	2026-04-23	7.3	157	13.73	13.27	8.91	19.96
La Rochelle	Antioche	Surface	2011-06-22	2026-07-03	15.0	327	14.84	15.31	6.30	21.76
Gironde	pk86	Surface	1997-03-03	2026-03-26	29.1	509	16.13	16.82	4.53	24.72
		Bottom	1997-03-03	2026-03-26	29.1	509	15.98	16.57	4.59	24.47
	pk52	Surface	1997-01-21	2026-03-25	29.2	554	17.55	18.55	3.06	27.76
		Bottom	1997-01-21	2026-03-25	29.2	554	17.17	18.09	2.97	26.77
	pk30	Surface	1997-01-20	2026-03-27	29.2	554	16.79	17.39	2.26	26.84
		Bottom	1997-01-20	2026-03-27	29.2	554	16.78	17.32	2.53	26.92
Arcachon	Comprian	Surface	2005-01-21	2026-04-23	21.3	447	15.76	15.45	4.80	27.41
	Eyrac	Surface	1997-01-15	2026-04-23	29.3	757	15.57	15.10	3.60	27.15
		Bottom	1997-01-15	2004-09-17	7.7	302	15.31	14.68	5.20	24.40
	Bouée 13	Surface	2005-01-21	2026-04-23	21.3	451	15.36	15.02	7.20	25.00
Banyuls	Sola	Surface	1997-03-13	2026-04-30	29.1	1244	16.77	16.56	8.53	26.13
		Bottom	1997-03-13	2026-04-30	29.1	1220	15.49	15.10	8.52	24.29
Sète	Sète	Surface	2015-02-17	2025-12-17	10.8	224	17.07	16.71	11.14	26.80
Marseille	Frioul	Surface	1997-01-28	2026-05-26	29.3	680	17.12	16.30	12.23	27.21
		Bottom	2004-01-16	2026-05-26	22.4	499	14.77	14.35	11.99	21.88
Villefranche-sur-Mer	Point B	Surface	1997-01-02	2024-05-28	27.4	1332	18.66	17.87	12.51	28.42
		Bottom	1997-01-02	2024-05-28	27.4	1327	15.36	14.97	12.45	24.73

2.4 Monthly climatologies

The climatology uses every individual observation, without prior averaging by year-month.

2.4.1 Wimereux

2.4.2 Luc-sur-Mer

2.4.3 Dinard

2.4.4 Roscoff

2.4.5 Brest

2.4.6 La Rochelle

2.4.7 Gironde

2.4.8 Arcachon

2.4.9 Banyuls

2.4.10 Sète

2.4.11 Marseille

2.4.12 Villefranche-sur-Mer

2.5 Monthly anomalies

Each anomaly is calculated for an individual observation relative to the monthly climatology; no monthly averaging is performed.

2.5.1 Wimereux

2.5.2 Luc-sur-Mer

2.5.3 Dinard

2.5.4 Roscoff

2.5.5 Brest

2.5.6 La Rochelle

2.5.7 Gironde

2.5.8 Arcachon

2.5.9 Banyuls

2.5.10 Sète

2.5.11 Marseille

2.5.12 Villefranche-sur-Mer

2.6 Temporal trends

Trends are estimated from individual temperature anomalies using GLS models with an AR(1) correlation structure applied to observations in chronological order. Slopes are expressed in °C per decade.

GLS AR(1) trends in monthly temperature anomalies. Bold rows indicate significant slopes (p < 0.05).

Site	Station	Depth	N	Start date	End date	Time span (years)	Slope (°C per decade)	SE (°C per decade)	Lower 95% CI	Upper 95% CI	p-value	AR(1) rho	Status
Wimereux	Point L	Surface	327	1998-01-12	2026-06-15	28.4	0.4116	0.1125	0.1902	0.6330	0.0003	0.3630	GLS AR(1)
		Bottom	320	1998-01-27	2026-06-15	28.4	0.4954	0.1127	0.2736	0.7172	<0.0001	0.4254	GLS AR(1)
	Point C	Surface	416	1998-01-12	2026-06-15	28.4	0.5139	0.1004	0.3166	0.7111	<0.0001	0.3053	GLS AR(1)
		Bottom	406	1998-01-27	2026-06-15	28.4	0.5304	0.1017	0.3305	0.7303	<0.0001	0.3625	GLS AR(1)
Luc-sur-Mer	Smile	Surface	260	2013-04-09	2026-02-02	12.8	0.8600	0.1971	0.4718	1.2482	<0.0001	0.2026	GLS AR(1)
	Luc-sur-Mer	Surface	420	2007-01-04	2026-02-02	19.1	0.7674	0.1200	0.5315	1.0033	<0.0001	0.1518	GLS AR(1)
Dinard	Le Buron	Surface	269	2011-12-15	2024-11-28	13.0	-4.0244	3.2307	-10.3852	2.3365	0.2140	0.9456	GLS AR(1)
		Bottom	23	2011-12-15	2012-12-18	1.0	-2.6265	2.2066	-7.2154	1.9625	0.2472	-0.4835	GLS AR(1)
	Cézembre	Surface	205	2014-03-07	2023-12-18	9.8	0.6269	0.2210	0.1912	1.0626	0.0050	0.0633	GLS AR(1)
Roscoff	Estacade	Surface	690	1997-01-03	2026-07-23	29.6	0.2028	0.0477	0.1092	0.2964	<0.0001	0.3516	GLS AR(1)
	Astan	Surface	632	2000-02-28	2026-07-23	26.4	0.2197	0.0601	0.1018	0.3377	0.0003	0.5282	GLS AR(1)
		Bottom	631	2000-02-14	2026-07-23	26.4	0.2513	0.0570	0.1394	0.3632	<0.0001	0.5165	GLS AR(1)
Brest	Portzic	Surface	1367	1998-03-25	2026-04-27	28.1	0.2735	0.0483	0.1787	0.3683	<0.0001	0.5264	GLS AR(1)
	Lanvéoc	Surface	157	2019-01-08	2026-04-23	7.3	0.7638	0.2916	0.1877	1.3398	0.0097	0.0267	GLS AR(1)
La Rochelle	Antioche	Surface	327	2011-06-22	2026-07-03	15.0	0.6507	0.1941	0.2690	1.0325	0.0009	0.2251	GLS AR(1)
Gironde	pk86	Surface	509	1997-03-03	2026-03-26	29.1	0.2901	0.1051	0.0836	0.4965	0.0060	0.3777	GLS AR(1)
		Bottom	509	1997-03-03	2026-03-26	29.1	0.2985	0.1059	0.0906	0.5065	0.0050	0.4280	GLS AR(1)
	pk52	Surface	554	1997-01-21	2026-03-25	29.2	0.0034	0.1324	-0.2567	0.2635	0.9794	0.3864	GLS AR(1)
		Bottom	554	1997-01-21	2026-03-25	29.2	0.2440	0.1376	-0.0263	0.5144	0.0767	0.5088	GLS AR(1)
	pk30	Surface	554	1997-01-20	2026-03-27	29.2	0.3225	0.1495	0.0288	0.6162	0.0314	0.5235	GLS AR(1)
		Bottom	554	1997-01-20	2026-03-27	29.2	0.3398	0.1514	0.0425	0.6371	0.0252	0.5295	GLS AR(1)
Arcachon	Comprian	Surface	447	2005-01-21	2026-04-23	21.3	0.6835	0.1360	0.4162	0.9507	<0.0001	0.1053	GLS AR(1)
	Eyrac	Surface	757	1997-01-15	2026-04-23	29.3	0.3199	0.0759	0.1708	0.4689	<0.0001	0.1669	GLS AR(1)
		Bottom	302	1997-01-15	2004-09-17	7.7	-0.7655	0.4878	-1.7254	0.1943	0.1176	0.1311	GLS AR(1)
	Bouée 13	Surface	451	2005-01-21	2026-04-23	21.3	0.5378	0.1190	0.3039	0.7717	<0.0001	0.1511	GLS AR(1)
Banyuls	Sola	Surface	1244	1997-03-13	2026-04-30	29.1	0.3774	0.0741	0.2320	0.5228	<0.0001	0.4763	GLS AR(1)
		Bottom	1220	1997-03-13	2026-04-30	29.1	0.3692	0.0637	0.2443	0.4941	<0.0001	0.1686	GLS AR(1)
Sète	Sète	Surface	224	2015-02-17	2025-12-17	10.8	0.4869	0.4794	-0.4580	1.4317	0.3110	0.1624	GLS AR(1)
Marseille	Frioul	Surface	680	1997-01-28	2026-05-26	29.3	0.4017	0.0907	0.2235	0.5798	<0.0001	0.0394	GLS AR(1)
		Bottom	499	2004-01-16	2026-05-26	22.4	0.2869	0.0863	0.1172	0.4565	0.0010	0.1798	GLS AR(1)
Villefranche-sur-Mer	Point B	Surface	1332	1997-01-02	2024-05-28	27.4	0.3781	0.0641	0.2525	0.5038	<0.0001	0.3962	GLS AR(1)
		Bottom	1327	1997-01-02	2024-05-28	27.4	0.2181	0.0450	0.1298	0.3065	<0.0001	0.3130	GLS AR(1)

2.6.1 Wimereux

2.6.2 Luc-sur-Mer

2.6.3 Dinard

2.6.4 Roscoff

2.6.5 Brest

2.6.6 La Rochelle

2.6.7 Gironde

2.6.8 Arcachon

2.6.9 Banyuls

2.6.10 Sète

2.6.11 Marseille

2.6.12 Villefranche-sur-Mer