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 Temperature quality flags by monitoring site

Percentages are calculated from observations with a valid date and temperature at a surface or bottom sampling level, before filtering by qT. Missing qT values are included in the denominator and shown separately.

Percentage of temperature quality flags (qT) by monitoring site

Site	Station	qT_2	qT_3	qT_4	qT_5	qT_6	qT_7	qT_9	Missing
Wimereux	Point L	68.5	2.5	0.0	0.0	28.0	1.1	0.0	0
Wimereux	Point C	66.3	2.6	0.0	0.0	30.2	1.0	0.0	0
Luc-sur-Mer	Smile	0.0	0.0	0.0	0.0	96.5	3.5	0.0	0
Luc-sur-Mer	Luc-sur-Mer	0.0	0.0	0.0	0.0	96.9	3.1	0.0	0
Dinard	Le Buron	96.6	0.0	0.0	0.0	0.0	3.4	0.0	0
Dinard	Cézembre	95.1	0.0	0.0	0.0	0.0	4.9	0.0	0
Roscoff	Estacade	99.1	0.3	0.0	0.0	0.0	0.6	0.0	0
Roscoff	Astan	99.4	0.0	0.2	0.0	0.0	0.3	0.0	0
Brest	Portzic	87.6	0.9	0.0	0.0	5.9	5.5	0.2	0
Brest	Lanvéoc	86.6	0.6	0.0	0.0	0.0	12.7	0.0	0
La Rochelle	Antioche	86.9	0.6	0.0	0.0	2.1	10.4	0.0	0
Gironde	pk86	99.9	0.1	0.0	0.0	0.0	0.0	0.0	0
Gironde	pk52	99.4	0.6	0.0	0.0	0.0	0.0	0.0	0
Gironde	pk30	99.5	0.5	0.0	0.0	0.0	0.0	0.0	0
Arcachon	Comprian	96.0	0.2	0.0	0.0	0.0	3.8	0.0	0
Arcachon	Eyrac	71.3	0.1	0.0	0.0	0.0	28.6	0.0	0
Arcachon	Bouée 13	96.5	0.4	0.2	0.0	0.0	2.9	0.0	0
Banyuls	Sola	99.6	0.0	0.0	0.0	0.4	0.0	0.0	0
Sète	Sète	87.5	0.0	0.0	0.9	0.0	11.6	0.0	0
Marseille	Frioul	100.0	0.0	0.0	0.0	0.0	0.0	0.0	0
Villefranche-sur-Mer	Point B	98.7	0.1	0.0	0.0	0.0	1.2	0.0	0

2.2 Data filtering

Only temperature observations with quality flag qT_2 are retained for the data availability summaries, figures, descriptive statistics and trend analyses that follow.

2.3 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	1998-01-27	2026-06-15	28.4	224	1.0	1.0
		Bottom	1998-01-27	2026-06-15	28.4	219	50.0	50.0
	Point C	Surface	1998-01-27	2026-06-15	28.4	273	1.0	2.0
		Bottom	1998-01-27	2026-06-15	28.4	272	25.0	25.0
Dinard	Le Buron	Surface	2011-12-15	2024-11-28	13.0	259	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	195	1.0	1.0
Roscoff	Estacade	Surface	1997-01-03	2026-07-23	29.6	684	1.0	1.0
	Astan	Surface	2000-03-13	2026-07-23	26.4	628	1.0	1.0
		Bottom	2000-02-14	2026-07-23	26.4	628	60.0	60.0
Brest	Portzic	Surface	1998-03-25	2026-04-27	28.1	1197	2.0	2.0
	Lanvéoc	Surface	2019-01-28	2026-04-23	7.2	136	2.0	2.0
La Rochelle	Antioche	Surface	2013-01-04	2026-07-03	13.5	284	1.0	1.0
Gironde	pk86	Surface	1997-03-03	2026-03-26	29.1	508	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	551	1.0	1.0
		Bottom	1997-01-21	2026-03-25	29.2	550	2.0	9.0
	pk30	Surface	1997-01-20	2026-03-27	29.2	551	1.0	1.0
		Bottom	1997-01-20	2026-03-27	29.2	552	4.0	10.0
Arcachon	Comprian	Surface	2005-01-21	2026-04-23	21.3	429	1.0	8.0
	Eyrac	Surface	1997-01-15	2026-04-23	29.3	596	1.0	7.3
		Bottom	1997-01-15	2004-09-17	7.7	159	6.0	6.0
	Bouée 13	Surface	2005-01-21	2026-04-23	21.3	435	1.0	22.0
Banyuls	Sola	Surface	1997-03-13	2026-04-30	29.1	1240	3.0	3.0
		Bottom	1997-03-13	2026-04-30	29.1	1214	24.0	24.0
Sète	Sète	Surface	2015-02-17	2025-12-17	10.8	196	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	1312	1.0	2.0
		Bottom	1997-01-02	2024-05-28	27.4	1312	50.0	50.0

2.4 Data visualisation

2.4.1 Wimereux

2.4.2 Dinard

2.4.3 Roscoff

2.4.4 Brest

2.4.5 La Rochelle

2.4.6 Gironde

2.4.7 Arcachon

2.4.8 Banyuls

2.4.9 Sète

2.4.10 Marseille

2.4.11 Villefranche-sur-Mer

2.5 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	1998-01-27	2026-06-15	28.4	224	12.46	12.50	5.20	20.14
		Bottom	1998-01-27	2026-06-15	28.4	219	12.20	12.41	5.21	19.80
	Point C	Surface	1998-01-27	2026-06-15	28.4	273	12.30	12.13	4.93	20.80
		Bottom	1998-01-27	2026-06-15	28.4	272	12.13	11.96	4.92	20.30
Dinard	Le Buron	Surface	2011-12-15	2024-11-28	13.0	259	12.67	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	195	13.82	13.72	7.06	20.53
Roscoff	Estacade	Surface	1997-01-03	2026-07-23	29.6	684	13.14	13.23	7.60	17.50
	Astan	Surface	2000-03-13	2026-07-23	26.4	628	13.03	13.10	8.30	16.95
		Bottom	2000-02-14	2026-07-23	26.4	628	12.96	13.10	8.50	16.61
Brest	Portzic	Surface	1998-03-25	2026-04-27	28.1	1197	13.55	13.60	7.88	18.70
	Lanvéoc	Surface	2019-01-28	2026-04-23	7.2	136	13.69	13.22	8.91	19.96
La Rochelle	Antioche	Surface	2013-01-04	2026-07-03	13.5	284	14.71	14.92	8.36	21.76
Gironde	pk86	Surface	1997-03-03	2026-03-26	29.1	508	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	551	17.55	18.57	3.06	27.76
		Bottom	1997-01-21	2026-03-25	29.2	550	17.17	18.12	2.97	26.77
	pk30	Surface	1997-01-20	2026-03-27	29.2	551	16.79	17.42	2.26	26.84
		Bottom	1997-01-20	2026-03-27	29.2	552	16.78	17.32	2.53	26.92
Arcachon	Comprian	Surface	2005-01-21	2026-04-23	21.3	429	15.62	15.20	4.80	27.41
	Eyrac	Surface	1997-01-15	2026-04-23	29.3	596	15.51	15.10	5.10	27.15
		Bottom	1997-01-15	2004-09-17	7.7	159	14.99	14.35	5.20	24.20
	Bouée 13	Surface	2005-01-21	2026-04-23	21.3	435	15.30	14.94	7.20	25.00
Banyuls	Sola	Surface	1997-03-13	2026-04-30	29.1	1240	16.79	16.58	8.53	26.13
		Bottom	1997-03-13	2026-04-30	29.1	1214	15.49	15.11	8.52	24.29
Sète	Sète	Surface	2015-02-17	2025-12-17	10.8	196	17.09	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	1312	18.59	17.80	12.51	28.42
		Bottom	1997-01-02	2024-05-28	27.4	1312	15.35	14.96	12.45	24.73

2.6 Monthly climatologies

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

2.6.1 Wimereux

2.6.2 Dinard

2.6.3 Roscoff

2.6.4 Brest

2.6.5 La Rochelle

2.6.6 Gironde

2.6.7 Arcachon

2.6.8 Banyuls

2.6.9 Sète

2.6.10 Marseille

2.6.11 Villefranche-sur-Mer

2.7 Monthly anomalies

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

2.7.1 Wimereux

2.7.2 Dinard

2.7.3 Roscoff

2.7.4 Brest

2.7.5 La Rochelle

2.7.6 Gironde

2.7.7 Arcachon

2.7.8 Banyuls

2.7.9 Sète

2.7.10 Marseille

2.7.11 Villefranche-sur-Mer

2.8 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	224	1998-01-27	2026-06-15	28.4	0.4985	0.1399	0.2227	0.7743	0.0004	0.4079	GLS AR(1)
		Bottom	219	1998-01-27	2026-06-15	28.4	0.5167	0.1424	0.2360	0.7973	0.0004	0.4517	GLS AR(1)
	Point C	Surface	273	1998-01-27	2026-06-15	28.4	0.5352	0.1291	0.2810	0.7894	<0.0001	0.3457	GLS AR(1)
		Bottom	272	1998-01-27	2026-06-15	28.4	0.5452	0.1283	0.2925	0.7978	<0.0001	0.4080	GLS AR(1)
Dinard	Le Buron	Surface	259	2011-12-15	2024-11-28	13.0	-3.9856	3.3196	-10.5226	2.5514	0.2310	0.9469	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	195	2014-03-07	2023-12-18	9.8	0.7009	0.2104	0.2859	1.1160	0.0010	0.0102	GLS AR(1)
Roscoff	Estacade	Surface	684	1997-01-03	2026-07-23	29.6	0.2040	0.0478	0.1101	0.2979	<0.0001	0.3537	GLS AR(1)
	Astan	Surface	628	2000-03-13	2026-07-23	26.4	0.2372	0.0581	0.1232	0.3512	<0.0001	0.5207	GLS AR(1)
		Bottom	628	2000-02-14	2026-07-23	26.4	0.2692	0.0585	0.1544	0.3840	<0.0001	0.5535	GLS AR(1)
Brest	Portzic	Surface	1197	1998-03-25	2026-04-27	28.1	0.2632	0.0472	0.1706	0.3557	<0.0001	0.4970	GLS AR(1)
	Lanvéoc	Surface	136	2019-01-28	2026-04-23	7.2	0.8326	0.3189	0.2020	1.4633	0.0100	0.0688	GLS AR(1)
La Rochelle	Antioche	Surface	284	2013-01-04	2026-07-03	13.5	0.8824	0.2093	0.4704	1.2944	<0.0001	0.1705	GLS AR(1)
Gironde	pk86	Surface	508	1997-03-03	2026-03-26	29.1	0.2947	0.1049	0.0886	0.5007	0.0051	0.3765	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	551	1997-01-21	2026-03-25	29.2	0.0003	0.1303	-0.2557	0.2563	0.9980	0.3769	GLS AR(1)
		Bottom	550	1997-01-21	2026-03-25	29.2	0.2300	0.1367	-0.0385	0.4984	0.0931	0.5062	GLS AR(1)
	pk30	Surface	551	1997-01-20	2026-03-27	29.2	0.3335	0.1494	0.0400	0.6269	0.0260	0.5230	GLS AR(1)
		Bottom	552	1997-01-20	2026-03-27	29.2	0.3475	0.1508	0.0512	0.6437	0.0216	0.5263	GLS AR(1)
Arcachon	Comprian	Surface	429	2005-01-21	2026-04-23	21.3	0.6770	0.1404	0.4011	0.9529	<0.0001	0.1153	GLS AR(1)
	Eyrac	Surface	596	1997-01-15	2026-04-23	29.3	0.4015	0.0810	0.2423	0.5607	<0.0001	0.1085	GLS AR(1)
		Bottom	159	1997-01-15	2004-09-17	7.7	-0.4953	0.5332	-1.5485	0.5579	0.3544	-0.0015	GLS AR(1)
	Bouée 13	Surface	435	2005-01-21	2026-04-23	21.3	0.5443	0.1229	0.3028	0.7858	<0.0001	0.1648	GLS AR(1)
Banyuls	Sola	Surface	1240	1997-03-13	2026-04-30	29.1	0.3785	0.0743	0.2328	0.5242	<0.0001	0.4764	GLS AR(1)
		Bottom	1214	1997-03-13	2026-04-30	29.1	0.3611	0.0640	0.2354	0.4867	<0.0001	0.1757	GLS AR(1)
Sète	Sète	Surface	196	2015-02-17	2025-12-17	10.8	0.5064	0.4899	-0.4598	1.4727	0.3026	0.1513	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	1312	1997-01-02	2024-05-28	27.4	0.3669	0.0646	0.2402	0.4936	<0.0001	0.3932	GLS AR(1)
		Bottom	1312	1997-01-02	2024-05-28	27.4	0.2174	0.0455	0.1282	0.3066	<0.0001	0.3121	GLS AR(1)

2.8.1 Wimereux

2.8.2 Dinard

2.8.3 Roscoff

2.8.4 Brest

2.8.5 La Rochelle

2.8.6 Gironde

2.8.7 Arcachon

2.8.8 Banyuls

2.8.9 Sète

2.8.10 Marseille

2.8.11 Villefranche-sur-Mer