Sea Ledger, April 2023

2023-04-01 to 2023-04-30 · archive

issued: 679
warning-days in force: 13,758
in force at month end: 470
sea × type cells: 235

baseline: same month, previous 5 years (2022-04, 2021-04, 2020-04, 2019-04, 2018-04)

By type

type	issued	warning-days	in force at end
Exercises	158	1,107	46
Icebergs	92	99.6	4
Incidents	83	1,035.1	25
Surveys	80	3,007.1	103
Missiles	59	420.1	9
Nav aids	53	4,382.6	151
Quakes	45	138	7
Derelicts	28	190.7	9
Cable ops	21	592.7	19
Other	20	647.2	28
Towing	17	15.3	1
Debris	7	106.9	5
Spills	7	152	4
Wrecks	5	1,287.2	41
Containers	2	36	1
Restricted	1	60	2
Piracy	1	3	0
Volcanic	0	237.7	7
Mines	0	60	2
Structures	0	120	4
Ordnance	0	30	1
War risk	0	30	1

By sea and type · 200 cells, most issued first

cell	issued	warning-days	at end	longest d	vs 5 y
Exercises · North Pacific Ocean	38	310.1	15	65	1.7× / 22.8
Icebergs · Southern Ocean	30	29.3	1	29	0.8× / 35.2
Icebergs · South Atlantic Ocean	30	29	1	30	1.3× / 23.2
Icebergs · Labrador Sea	29	34.3	2	31	1.3× / 22
Missiles · North Atlantic Oceansurge	24	150.5	2	29	2.7× / 8.8
Surveys · Arabian Seasurge	18	390.2	14	102	2.0× / 9
Towing · North Pacific Oceansurge	17	15.3	1	30	4.3× / 4
Exercises · Bay of Bengal	14	49	1	25	1.5× / 9.4
Exercises · Arabian Sea	12	65	3	33	1.1× / 11
Exercises · Celtic Seasurge	11	12.8	2	19	6.1× / 1.8
Incidents · Caribbean Seasurge	10	104	5	29	4.5× / 2.2
Quakes · South Pacific Ocean	10	31.2	4	31	1.0× / 9.6
Incidents · North Pacific Ocean	9	130.1	1	31	0.6× / 16.4
Incidents · South Pacific Oceansurge	9	112.8	4	40	2.0× / 4.4
Incidents · Indian Ocean	9	65.9	2	41	1.3× / 7
Exercises · South Pacific Ocean	9	35	3	23	1.1× / 8.4
Exercises · Andaman or Burma Seasurge	9	23.2	1	21	3.5× / 2.6
Surveys · North Atlantic Ocean	8	733.1	25	313	1.1× / 7.2
Nav aids · North Atlantic Oceanlong running	8	307.2	11	745	1.7× / 4.8
Cable ops · Arabian Seasurge	8	152.4	6	74	3.3× / 2.4
Incidents · Mediterranean Sea - Eastern Basin	8	70.9	4	27	1.5× / 5.4
Exercises · South Atlantic Ocean	8	68.7	2	304	1.2× / 6.8
Exercises · North Atlantic Ocean	8	63.7	3	134	1.7× / 4.6
Missiles · North Pacific Ocean	8	47.9	1	61	1.9× / 4.2
Quakes · Indian Oceansurge	8	26.9	0	—	3.3× / 2.4
Nav aids · North Sea	7	143.1	5	325	1.0× / 7.2
Derelicts · South Pacific Oceansurge	7	47.3	2	209	2.2× / 3.2
Nav aids · South Atlantic Ocean	6	1,358.8	45	261	0.5× / 13.2
Surveys · Persian Gulflong running	6	359.6	11	832	0.8× / 7.6
Surveys · South Atlantic Ocean	6	186.8	5	217	0.3× / 17.8
Surveys · Indian Oceanlong running	6	177.9	6	379	1.8× / 3.4
Incidents · South China Sea	6	105.3	2	52	0.3× / 23.6
Incidents · South Atlantic Ocean	6	88	0	—	1.0× / 6.2
Exercises · Black Sealong running	6	69.6	2	403	0.5× / 12.2
Exercises · Laccadive Seasurge	6	34.1	1	21	3.3× / 1.8
Missiles · Gulf of Mexicosurge	6	31.6	0	—	15× / 0.4
Derelicts · Caribbean Seasurge	6	19.8	0	—	7.5× / 0.8
Incidents · North Atlantic Ocean	5	144.4	2	177	0.6× / 7.8
Surveys · Bay of Bengalsurge	5	124.1	5	149	2.3× / 2.2
Nav aids · Coral Sea	5	76.2	3	48	0.9× / 5.8
Nav aids · Indian Oceansurge	5	57.5	4	24	3.1× / 1.6
Surveys · Norwegian Seasurge	5	44	3	16	6.3× / 0.8
Exercises · Gulf of Mexicosurge	5	29.5	0	—	8.3× / 0.6
Exercises · Barentsz Sea	5	29.3	2	32	1.7× / 3
Missiles · South Pacific Ocean	5	26.5	3	14	1.5× / 3.4
Exercises · Bay of Biscaysurge	5	15.9	0	—	5.0× / 1
Debris · North Pacific Oceansurge	5	13.7	1	32	8.3× / 0.6
Surveys · Mediterranean Sea - Western Basinsurge	5	12.7	0	—	3.6× / 1.4
Exercises · Coral Seasurge	5	9.3	1	5	8.3× / 0.6
Other · North Atlantic Ocean	4	127.8	6	223	0.6× / 6.8
Surveys · Caribbean Seasurge	4	60	2	182	5.0× / 0.8
Missiles · South Atlantic Oceansurge	4	25.4	0	—	10× / 0.4
Quakes · North Pacific Ocean	4	12	0	—	1.3× / 3
Derelicts · North Atlantic Ocean	4	11.5	1	32	1.3× / 3
Nav aids · Caribbean Sealong running	3	731.4	25	803	1.9× / 1.6
Nav aids · South Pacific Oceanlong running	3	580.1	20	402	0.8× / 4
Surveys · Laccadive Seasurgelong running	3	101.6	4	442	7.5× / 0.4
Spills · Gulf of Mexico	3	67	2	41	0.6× / 5.4
Incidents · Gulf of Mexicosurge	3	58.2	3	119	3.0× / 1
Missiles · Barentsz Sea	3	40	0	—	0.8× / 4
Surveys · Bass Straitsurge	3	39	3	24	7.5× / 0.4
Derelicts · South Atlantic Ocean	3	35.1	1	43	1.9× / 1.6
Exercises · Japan Seasurge	3	33.1	2	34	3.8× / 0.8
Surveys · Philippine Seasurge	3	30.4	0	—	15× / 0.2
Missiles · Indian Ocean	3	23.8	2	33	0.8× / 3.6
Exercises · Sea of Okhotsksurge	3	16.1	0	—	7.5× / 0.4
Quakes · Bismarck Seasurge	3	9	0	—	2.5× / 1.2
Incidents · Laccadive Sea	3	7.1	0	—	1.4× / 2.2
Nav aids · Inner Seas off the West Coast of Scotland	3	6.4	0	—	1.3× / 2.4
Incidents · Coral Sea	3	3.3	1	30	0.8× / 4
Other · South Pacific Oceansurge	3	1.2	1	7	3.8× / 0.8
Nav aids · North Pacific Oceanlong running	2	136	5	389	0.4× / 5
Wrecks · Caribbean Sea	2	126.8	4	221	10× / 0.2
Surveys · Black Sea	2	106.4	5	87	1.3× / 1.6
Surveys · South Pacific Ocean	2	74.8	2	40	1.0× / 2
Surveys · Gulf of Mexico	2	53	2	150	10× / 0.2
Other · South Atlantic Ocean	2	50.1	3	103	3.3× / 0.6
Derelicts · Laccadive Sea	2	33.4	2	312	10× / 0.2
Derelicts · Bay of Bengal	2	31.1	2	317	1.7× / 1.2
Spills · The Coastal Waters of Southeast Alaska and British Columbia	2	28	0	—	2.5× / 0.8
Missiles · Celtic Seanew	2	26.2	0	—	new / 0
Nav aids · Great Australian Bight	2	23.2	0	—	5.0× / 0.4
Spills · North Pacific Ocean	2	20	1	30	0.6× / 3.4
Incidents · Gulf of Californianew	2	18.6	1	20	new / 0
Cable ops · North Pacific Ocean	2	17.9	0	—	1.7× / 1.2
Incidents · Sulu Seanew	2	16.9	0	—	new / 0
Exercises · Gulf of Californianew	2	11.7	0	—	new / 0
Exercises · Tasman Sea	2	9.3	0	—	10× / 0.2
Exercises · Mozambique Channel	2	8.7	0	—	2.5× / 0.8
Quakes · Andaman or Burma Sea	2	6	0	—	5.0× / 0.4
Quakes · Arabian Sea	2	6	0	—	5.0× / 0.4
Quakes · Banda Sea	2	6	0	—	1.7× / 1.2
Quakes · Solomon Sea	2	6	0	—	3.3× / 0.6
Quakes · South Atlantic Ocean	2	6	1	21	1.1× / 1.8
Quakes · Arafura Seanew	2	4.9	2	2	new / 0
Nav aids · Bay of Bengal	2	4.4	0	—	2.0× / 1
Missiles · Laccadive Sea	2	3.6	0	—	2.0× / 1
Nav aids · Laccadive Sea	1	122	4	320	2.5× / 0.4
Other · Persian Gulf	1	121.5	5	269	2.5× / 0.4
Wrecks · South Atlantic Ocean	1	120	4	338	1.0× / 1
Nav aids · Bay of Biscay	1	90.1	3	275	new / 0
Nav aids · Irish Sea and St. George's Channel	1	34.6	2	304	1.0× / 1
Other · Bay of Biscay	1	32.4	1	102	2.5× / 0.4
Other · Coral Sealong running	1	32.4	1	375	2.5× / 0.4
Cable ops · Mozambique Channel	1	32	0	—	new / 0
Nav aids · Celtic Sea	1	31.3	2	254	1.3× / 0.8
Debris · Bay of Biscay	1	30.2	2	235	new / 0
Cable ops · Indian Ocean	1	30	1	36	5.0× / 0.2
Restricted · Indian Ocean	1	30	1	317	new / 0
Wrecks · South Pacific Ocean	1	27.9	1	27	1.7× / 0.6
Surveys · North Sea	1	27.5	1	27	0.4× / 2.4
Cable ops · Red Sea	1	23.6	0	—	new / 0
Other · North Pacific Ocean	1	20.4	0	—	0.8× / 1.2
Wrecks · English Channel	1	19.4	1	19	2.5× / 0.4
Incidents · Mediterranean Sea - Western Basin	1	15.9	0	—	1.7× / 0.6
Cable ops · Caribbean Sea	1	15.2	0	—	new / 0
Incidents · Philippine Sea	1	15.1	0	—	0.4× / 2.4
Incidents · Japan Sea	1	14	0	—	new / 0
Other · North Sea	1	13.7	1	13	1.7× / 0.6
Surveys · Andaman or Burma Sea	1	13.5	1	13	2.5× / 0.4
Cable ops · Andaman or Burma Sea	1	13.4	1	13	new / 0
Cable ops · South Pacific Ocean	1	12.1	1	12	0.5× / 2
Exercises · Mediterranean Sea - Western Basin	1	10	1	9	0.3× / 3.8
Exercises · Norwegian Sea	1	10	0	—	2.5× / 0.4
Cable ops · Ionian Sea	1	9.8	0	—	new / 0
Other · Gulf of Mexico	1	8.3	0	—	1.7× / 0.6
Missiles · Arctic Ocean	1	7.8	0	—	2.5× / 0.4
Cable ops · North Atlantic Ocean	1	7.8	1	7	0.2× / 4.6
Cable ops · South China Sea	1	6.9	1	34	1.3× / 0.8
Missiles · East Siberian Sea	1	6.8	0	—	new / 0
Incidents · Arafura Sea	1	6.6	0	—	1.3× / 0.8
Exercises · Caribbean Sea	1	5.9	0	—	1.0× / 1
Exercises · Philippine Sea	1	4.7	1	4	0.5× / 2
Cable ops · South Atlantic Ocean	1	4.6	0	—	1.3× / 0.8
Derelicts · South China Sea	1	4.6	0	—	1.0× / 1
Cable ops · Mediterranean Sea - Western Basin	1	4.5	0	—	0.6× / 1.6
Nav aids · Tasman Sea	1	4.5	0	—	1.7× / 0.6
Icebergs · Barentsz Sea	1	3	0	—	1.7× / 0.6
Debris · Bay of Bengal	1	3	0	—	2.5× / 0.4
Containers · Bay of Biscay	1	3	0	—	new / 0
Derelicts · English Channel	1	3	0	—	5.0× / 0.2
Quakes · Flores Sea	1	3	0	—	new / 0
Other · Indian Ocean	1	3	0	—	1.0× / 1
Quakes · Java Sea	1	3	0	—	new / 0
Icebergs · Kara Sea	1	3	0	—	0.8× / 1.2
Quakes · Mediterranean Sea - Eastern Basin	1	3	0	—	new / 0
Quakes · Molukka Sea	1	3	0	—	1.0× / 1
Other · Mozambique Channel	1	3	0	—	2.5× / 0.4
Containers · North Atlantic Ocean	1	3	0	—	5.0× / 0.2
Piracy · North Atlantic Ocean	1	3	0	—	2.5× / 0.4
Quakes · Philippine Sea	1	3	0	—	0.4× / 2.8
Quakes · Sea of Okhotsk	1	3	0	—	new / 0
Quakes · South China Sea	1	3	0	—	2.5× / 0.4
Quakes · Southern Ocean	1	3	0	—	1.7× / 0.6
Derelicts · Gulf of Mexico	1	2.6	1	2	new / 0
Other · Mediterranean Sea - Eastern Basin	1	2.4	1	2	2.5× / 0.4
Exercises · Eastern China Sea	1	2.3	0	—	new / 0
Other · Tyrrhenian Sea	1	2.2	1	2	5.0× / 0.2
Other · Timor Sea	1	1.7	1	1	5.0× / 0.2
Incidents · Labrador Sea	1	1.2	0	—	1.7× / 0.6
Nav aids · Gulf of Alaska	1	1.1	0	—	1.3× / 0.8
Icebergs · North Atlantic Ocean	1	1	0	—	0.1× / 7.4
Derelicts · North Sea	1	0.8	0	—	new / 0
Incidents · Ceram Sea	1	0.4	0	—	5.0× / 0.2
Incidents · Gulf of Thailand	1	0.3	0	—	0.6× / 1.6
Incidents · Timor Sea	1	0.2	0	—	1.7× / 0.6
Nav aids · Gulf of St. Lawrence	1	0.1	0	—	new / 0
Nav aids · Gulf of Mexicolong running	0	240	8	758	0.0× / 1.8
Wrecks · The Northwestern Passageslong running	0	205.6	5	605	— / 0
Cable ops · Persian Gulflong running	0	180	6	626	0.0× / 0.4
Wrecks · Persian Gulflong running	0	180	6	457	0.0× / 0.2
Volcanic · Philippine Sealong running	0	180	6	863	— / 0
Exercises · Aegean Sea	0	150	5	118	0.0× / 9.6
Surveys · The Northwestern Passages	0	150	5	254	— / 0
Wrecks · Arabian Sea	0	125	4	344	0.0× / 1
Surveys · Kara Sea	0	120	4	293	— / 0
Wrecks · Laccadive Sea	0	92.5	3	136	0.0× / 0.4
Wrecks · South China Sealong running	0	90	3	1,515	0.0× / 0.6
Other · Caribbean Sealong running	0	73.7	2	549	0.0× / 0.6
Nav aids · Arabian Sealong running	0	70.5	2	550	0.0× / 0.4
Other · Arabian Sealong running	0	62.5	2	598	0.0× / 0.8
Surveys · Barentsz Sea	0	60	2	293	0.0× / 0.6
Mines · Black Sealong running	0	60	2	430	— / 0
Wrecks · Hudson Bay	0	60	2	184	— / 0
Wrecks · North Atlantic Oceanlong running	0	60	2	704	0.0× / 0.2
Wrecks · North Sealong running	0	60	2	505	0.0× / 0.8
Nav aids · Persian Gulf	0	60	2	341	0.0× / 0.6
Structures · South Atlantic Ocean	0	60	2	275	0.0× / 0.6
Spills · North Atlantic Ocean	0	37	1	283	0.0× / 2
Missiles · Aegean Sea	0	30	1	118	— / 0
Nav aids · Andaman or Burma Sea	0	30	1	223	0.0× / 0.8
Nav aids · Arctic Ocean	0	30	1	221	— / 0
Surveys · Arctic Ocean	0	30	1	231	— / 0
Nav aids · Barentsz Sea	0	30	1	169	— / 0
Nav aids · Beaufort Sea	0	30	1	262	— / 0
Nav aids · Bering Sea	0	30	1	128	0.0× / 0.2
Other · Black Sea	0	30	1	42	0.0× / 0.6
War risk · Black Sealong running	0	30	1	404	— / 0
Wrecks · Coral Sea	0	30	1	303	— / 0
Other · English Channel	0	30	1	97	0.0× / 0.6

Cite: seahazards.com Sea Ledger, 2023-04, retrieved 2026-09-03

Not for navigation. Warning-days = days each warning was in force within the month, summed. Only warnings we display are counted; the ratio compares warnings issued with the mean of the reference months.