Baltic Sea Submarine Operations - Russia, Swedeen and Finland.

 In the map above the lighter the blue the shallower the water. The average depth of the Baltic Sea is 53 meters but the maximum depth is 459 meters. 459 meters is more than deep enough for submarines to hide in - if they choose the right hiding places - and those hiding places do not conceal the presence of an opponent's sea-floor (or tethered) sensors. (Map courtesy European Environment Agency)
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The Baltic Sea presents a challenging and dangerous submarine operating area in peacetime due to its undersea geography. This geography includes overall shallow and highly variable sea depths, many rocks and islands making for many narrows and rocks to get stuck in or collide with. However there  also many sea-floor depressions/variations to hide in.

In peacetime and wartime the intensity of ASW surveillance makes submarine operations on the surface and even at snorting depth dangerous. In Baltic operations quiet on-battery and/or on-AIP operation may be essential. It is probably no coincidence that the two nations that have developed the most efficient and commercially successful AIP systems (Germany (with fuel cell) and Sweden (Stirling engine)) may well spend most of their operating time in the Baltic.

The approaches to sea bases and coastal cities/ports frequently have sensor protections using  undersea arrays such as:

-  Malsten station (old probably non-operational hydrophones/sonar and magnetic anomaly) and much more operational, modern and geographically dispersed equipment

-  approaches to Helsinki Harbour (hydrophones/sonar, magnetic anomaly and more modern sensors)

-  Russian Baltic Fleet Base at Kaliningrad Enclave much more extensive and intensive. Few details about Russian hydrophones escape the Russian information censors. Naturally Russians submarines have many types of ASW sensors and the Russian Northern Fleet deploys test sensors

Russian Submarine Operations

Little seems to be known in the open-source world about Russian submarine operations in the Baltic.  Russian Kilo submarines and even Russia's one or two Ladas appear unsuited due to their relatively large size and lack of (known) AIP.

Russia, of course, has relied on highly developed nuclear propulsion solution for its AIP-like needs. But the Baltic is the wrong environment for nuclear propulsion as nuclear is assumed to be noisier than AIP, tends to preference large submarine solutions far heavier than 2,000 tons (surfaced), promotes speed which is a major danger in Baltic operations and nuclear submarines are an expensive asset to be at risk from highly intensive Baltic ASW forces and dangerous natural geography of the Baltic.

Russia submarines may well have been detected by Baltic countries hundreds of times since 1945 carrying out what look suspiciously like intelligence gathering missions in those countries territorial waters. The number of Russian submarines publically reported may well have been kept secret from Baltic and international publics due to:

-  the need to keep secret the efficiency of anti-submarine sensors (including sea-floor arrays) in detecting Russian (or friendly countries)

-  the much greater political, economic and military power of Russia compared to all other Baltic counties. Non-NATO Baltic countries Sweden and Finland are particularly careful not to offend the Russian giant by publically identifying clearly Russian submarine acoustic signatures and radio transmissions.

-  normal diplomatic practice which keeps sensitive international issues secret

-  the natural secrecy of Governments-Navies relating to all submarine operations

-  for a defending Navy (like Sweden's) to be publically seen as unable to counter submarine intelligence gathering against one's country can be embarrassing all round.

-  as the weaker country, compared to Russia, Sweden is forced by Russia or finds it more politically convenient, to recant and deny there was any Russian submarine incursion in the first place

Note how the detection and weaker country recanting process plays out in Russia vs Sweden October 17-24, 2014:

"A large military operation is launched to search for an allegedly damaged submarine in Kanholmsfjärden in the Stockholm archipelago. Encrypted transmissions sent on an emergency radio frequency used by Russian units were recorded. The sources of the transmissions were identified as a submarine and a military site in the Kaliningrad [Russian Naval Base] region.^{[14][15][16][17]} On 19 October [2014] the military said there had been three separate sightings and released a [photograph] of the unidentified submarine to the public.^[18] There were also suggestions that the Russian Oil-tanker NS Concord was involved as a mother-ship for smaller underwater vehicles as it maintained a pattern of criss-crossing outside Stockholm during the investigation.^[19] A Russian research ship equipped with a submarine holding bay, R/V Professor Logachev,^[20][21] was also in the area and turned off its location transponder.^[22][23] 

Several days later, the hunt was still on as [Swedish] officials were certain that foreign underwater operations were still ongoing.^[24] More than 100 sightings were now reported, said [Swedish]  Supreme Commander Göransson.^[25] Paul Schwartz at Center for Strategic and International Studies, CSIS, said the photograph could be a Russian Lada-class submarine.^[26] Sources later said it was certainly at least one mini-submarine and that advanced image analysis "reveals part of a submarine superstructure with two masts behind it".^[27] On April 2015 Rear Admiral Anders Grenstad has told Swedish newspapers that the Armed Forces reported to the Swedish government that [despite the mountain of evidence] the suspected underwater vessel was in fact only a civilian “working boat” [Such is the need to deceive for bilateral relations between the Russian giant and its weaker Baltic neighbours].^[28]"

This October 2014 Submarine Matters article contains more detailed descriptions of recent  Russian mini-submarines in the Baltic.

Tomorrow some surprisingly advanced Russian UUVs will be revealed.

Pete