The Baltic in winter — a shore without the seasonal postcard

What lies behind the traces

Four processes, five traces

The process descriptions come from version V2 and have been kept in a shortened form. The references [1], [2] and [3] lead to the sources, which were not reopened in this version, so the descriptions should be treated as unverified. Each process has its own trace on the cross-section, not its own card.

01
Fast ice

Medium
Frozen brackish sea water.

Condition and recognition
Anchored to the shore or to shoals; forms a solid sheet. Sea water loses heat; salt lowers the freezing point.

Description from the source (per V2, to be checked)
What matters is the link with the land, not the white colour of the sheet alone. Salt lowers the freezing temperature of the water, so frost in the air alone does not describe the whole situation. [1]

Trace on the cross-section: B · ice sheet near the shore
02
Drifting floes

Medium
Floating floes, broken-up cover.

Condition and recognition
Driven by wind and sea currents. Pieces may override one another and form piled-up ridges (hummocks).

Description from the source (per V2, to be checked)
Floating pieces, cracks and crowding. When ice fields press against each other, pieces override one another and pile up into ridges. [1]

Traces on the cross-section: A · floes and D · ridge on the beach
03
Spray icing

Medium
Ice building up from spray.

Condition and recognition
Sea water splashes and freezes on cold structures. The sea surface stays liquid and wavy.

Description from the source (per V2, to be checked)
Icing of a structure does not mean that the sea has become covered by an ice sheet. [2]

Trace on the cross-section: C · ice on piles
04
Storm surge

Medium
High sea water level.

Condition and recognition
Wind pushing the water moves masses of it towards the shore. Waves reach far up the beach and undercut dunes; frost is not necessary.

Description from the source (per V2, to be checked)
According to the V2 description, most storms on the Baltic Sea fall in the cool half of the year, from September to March. [3]

Trace on the cross-section: E · undercut dune

The same relationship without clicking

All readings at once

The table shows how each trace relates to the process description for four water states. The symbol tells only about consistency with the description, not about what really happened on the shore. The current selection from the cross-section is outlined in orange.

Reading: trace × water state
Trace	Don't know	Cover still	Floes moving	Waves open water
A · Floes	inconclusive	tension	consistent	consistent
B · Ice sheet	inconclusive	consistent	tension	tension
C · Piles	inconclusive	tension	inconclusive	consistent
D · Ridge	inconclusive	inconclusive	consistent	inconclusive
E · Dune	inconclusive	tension	inconclusive	consistent

● consistent with the process description · △ tension, to be checked · ○ inconclusive. Missing data on the water is a separate state (“don't know”), not zero and not a “calm sea”.

Reading of each trace

A Floating pieces of floe ice with cracks → drifting floes (02)

Most common reading: Drifting floes (02)
May co-occur with: Fast ice (01): floes may sit next to the cover in deeper water. Storm surge (04): high water and wind can push floes onto the shore.
Where this is on the cross-section: Trace A lies furthest from the shore; the frame covers several pieces and the cracks between them. The arrow in Frame II is an example of wind pressure.
What else to check: Whether the pieces move relative to the shore (photographs from the same spot at two dates) and whether there is water between them. Observe from land only.
What the trace does not prove: It does not say where the floes are drifting or whether the shore is accessible. This is not a navigation warning.

Water: don't knowFloating pieces alone do not say whether they are moving. Floe ice is ice driven by wind and currents; a cracked but stationary cover is a different description from drift. A second frame in time is needed.
Water: still ice coverTension: floes drift, but here the water lies under a stationary cover. Cracks in a standing cover describe something other than drift; movement shows only in two dates from the same spot.
Water: moving floesConsistent with the description of drifting floes: floating pieces, cracks and movement under the influence of wind and currents. When crowded, pieces override one another and pile up into ridges.
Water: open with wavesConsistent with the description: floes float on water, so patches of open water and waves may occur together with them. Wind and waves can break the ice; the direction of drift will emerge only from observing movement.

B Solid ice sheet near the shore → fast ice (01)

Most common reading: Fast ice (01)
May co-occur with: Drifting floes (02): solid ice on shallows may border a field of moving floes in a deeper channel.
Where this is on the cross-section: Trace B lies closer to the shore, but the frame does not show whether the sheet reaches the land. That is visible only in the wider Frame I, to the right of the frame. Dashed bracket in Frame II: thickness unknown.
What else to check: Whether the sheet is joined to the shore or a shoal and whether it stays in place. White colour alone is not enough. Observe from land, without stepping onto the ice.
What the trace does not prove: It does not prove the thickness or load-bearing capacity of the ice and does not show that one can walk on it. Do not step onto sea ice.

Water: don't knowThe look of the sheet alone does not decide. Fast ice is a cover attached to land or a shoal and stationary; from one frame you cannot see whether that is so. Say what is happening with the water.
Water: still ice coverConsistent with the description of fast ice: a solid, stationary cover near the shore. This is a match to the description, not confirmation of the type of ice, its thickness or its permanence.
Water: moving floesTension: fast ice stays in place, but here something is moving. You may be seeing a field of floes, or the edge of fast ice beyond which floes begin. Which case it is will be decided only by a wider frame.
Water: open with wavesTension: a solid sheet damps small waves, so intense splashing suggests open water beyond the ice belt or breaking of the cover's edge. The trace and the water may belong to different zones.

C Ice on piles and groynes above the water → spray icing (03)

Most common reading: Spray icing (03)
May co-occur with: Storm surge (04): in a freezing storm the wind piles up water and creates waves washing the piles, and frost freezes the spray.
Where this is on the cross-section: The frame covers the heads of the piles with ice just above the waterline, and the waterline itself. Only the choice in step 2 says anything about its state.
What else to check: Whether the water at the structure is liquid and wavy, and whether the ice is fresh accretion or a relic of an earlier freezing storm. Today's temperature does not decide this.
What the trace does not prove: It does not prove that the sea is frozen. Iced piles, piers and groynes are not places to walk onto.

Water: don't knowIce on piles says nothing about the water around. Spray freezes on a structure when the sea stays liquid and wavy, but you cannot read the state of the sea from ice on wood alone.
Water: still ice coverTension: spray requires wavy, open water at the structure, but here there is a stationary cover. Ice on the piles may have formed earlier, before the sea froze; from one frame you cannot decide this.
Water: moving floesInconclusive: floes can damp waves at the shore, and spray requires open water between the floes and the structure. Whether such water is present has to be judged outside the frame.
Water: open with wavesConsistent with the description of spray icing: sea water splashes and freezes on cold structures, and the sea surface stays liquid and wavy.

D Ridge of ice and sand on the beach → floes overriding and piling up (02)

Most common reading: Floes overriding and piling up (02)
May co-occur with: Storm surge (04): high water and wind can crush coastal ice and push floes onto the shore.
Where this is on the cross-section: Trace D lies on the beach between the waterline and the dune. The frame covers a ridge made of several blocks and part of the sandy slope. The ridge alone does not show when it formed.
What else to check: When the ridge formed: it may come from floes that have already gone. Comparing two visits to the same spot helps.
What the trace does not prove: It does not indicate a route along the beach and is not a safe observation spot.

Water: don't knowA ridge on the beach is a trace of ice pushed up mechanically, but it does not say whether floes are still present here. It is a record of an event, not of the state at the time of observation.
Water: still ice coverInconclusive: the ridge records earlier movement of floes, and a stationary cover may have come after it. The order of events shows only in two dates from the same spot.
Water: moving floesConsistent with the description: floes override one another and pile up into ridges of ice and sand pushed mechanically onto the beach, driven by wind and currents.
Water: open with wavesInconclusive: the ridge may have been left by floes that have already gone. Open water at the shore describes the present, the ridge describes the past.

E Fresh strandline and undercut dune → storm surge (04)

Most common reading: Storm surge (04)
May co-occur with: Spray icing (03) in a freezing storm or drifting floes (02) with ridges on the beach, depending on what else is visible.
Where this is on the cross-section: Trace E lies highest, at the foot of the dune. The frame covers the strandline, the dashed line of a conventional water level (read from the traces, not measured) and the undercut slope.
What else to check: Whether the strandline lies higher than usual at this spot and whether the undercutting is fresh. This requires knowing the place or comparing with another date.
What the trace does not prove: It does not give the water height or the time of the event and does not predict where the water will reach next time. This is not a forecast.

Water: don't knowA fresh strandline and an undercut dune show that the water reached high. The cause, wind pushing water towards the shore, can be confirmed only by wind and water level, which you cannot read from the frame.
Water: still ice coverTension: high water and waves reaching the dunes do not fit a stationary cover near the shore. The trace may come from an earlier storm; the order of events is needed.
Water: moving floesInconclusive: high water and wind can crush coastal ice and push floes onto the shore, but the strandline alone does not say which process prevailed.
Water: open with wavesConsistent with the description of storm surge: raised water level, waves reaching far up the beach and undercutting dunes. Frost is not necessary for this.

Limits and safety

What this page says and what it does not

This is not permission to go onto the ice

No observation, diagram or summary confirms that it is safe to step onto ice. Sea ice on the Baltic has variable salinity and creates thermal traps and brittle layers. Never step onto sea ice, onto an iced pier, or onto breakwaters and groynes washed by waves.

Give up the walk if water cuts off the way back. Before setting out, check the IMGW-PIB marine warnings and the current ice map of the Polish coast (always read the publication date of the operational file). The cross-section is not a plan or a route: pins A–E mark kinds of traces, not places where you can stand.

What a reading is

The reading rules are a manual interpretation of the process descriptions from V2 and of sources [1], [2], [3]. There is no classifier, scoring or confidence percentages here. Assigning forms to processes, especially where ice and waves co-occur, requires consultation with an oceanographer or the IMGW-PIB service; this page does not replace it.

The cross-section is a diagram of our own, not a map or a measurement. The shapes, distances and ×4 enlargement are conventional.

Co-occurrence of processes (description from V2)

Surge and spray icing (freezing storm): strong wind piles up water and creates waves washing the piles, and frost freezes the spray on structures.
Surge and drifting floes: storm wind and high water can crush coastal ice and push floes onto the shore, forming ridges on the beach.
Fast ice and drifting floes: solid ice on shallows borders a field of moving floes in a deeper channel.
Fast ice and intense splashing in one place: a solid sheet damps small waves, so splashing usually means open water beyond the ice belt or breaking of the cover's edge.

Air temperature

The third setting on the cross-section changes only what may be inferred from the trace, not the consistency result itself. The content below is read by the cross-section.

Frost is not a condition of surge: this trace forms without it too. At most, frost can add icing (03) or ice (01, 02) to it.
Frost in the air favours ice but does not prove it: salt lowers the freezing temperature of sea water [1], so air below 0°C alone does not describe the state of the water.
Above 0°C ice on piles does not prove ongoing icing: accretion from an earlier freezing storm melts slowly and can stay on the wood for many hours or days after the thaw arrives.
Above 0°C the ice cover near the shore is in a melting phase: it becomes porous and brittle. Do not infer its permanence from its appearance.
Surge does not require frost, so a thaw contradicts nothing here.
Above 0°C traces of frost may be a relic of an earlier event: the temperature at the time of observation does not say when the trace formed.
Temperature not selected: the reading assumes neither frost nor thaw.

What is not here

A second date at the same spot. I do not force one into the drawing: without two dates change cannot be shown, only faked. Instead, the same profile shows different water states.
Photographs on the page. The only one in the V2 material (groynes in Zingst, 5 February 2012) is a link, because the page works offline.
Numerical values: ice thickness, freezing temperatures, water height. Unknown is not zero.

What has gone compared with V2

The A/B curtain and the frame switch. They needed two dates at the same spot, and the “before” state was a drawing. Replaced by a single cross-section in which what we do not yet know changes: the state of the water.
A photograph loaded from the network. The photograph remains a link, not a rendering dependency.
Loading your own photographs. Without a way to check dates and place it added no knowledge; dropped.
A click on the frame with an interpretation depending on the height of the click. It was not based on the content of the image; replaced by pins assigned to specific traces.
A 14-feature analyser and four ready-made sets. Replaced by a single trace with water and air context; the notes on thaw and co-occurrence were kept.
A notebook of walks kept in browser storage. Dropped: the page saves nothing.

Sources

How we know this and what needs checking

The references and their short descriptions are carried over from version V2. In this version they were not reopened or verified. If the content of a source and the description on this page diverge, the source prevails.

SMHI: Olika typer av is till havs [Different types of ice at sea]. Mechanisms of sea water freezing, fast ice, drift and crowding of floes. Supports processes 01 and 02. To be rechecked.
Finnish Meteorological Institute: Ice accretion warnings. Ice growth from sea spray and meteorological factors. Supports process 03. To be rechecked.
IMGW-PIB: Wielkie fale na Bałtyku [Big waves on the Baltic]. Winds, storm waves and the dynamics of the cool half of the year (September–March). Supports process 04. To be rechecked.
IMGW-PIB: Mapa zlodzenia Bałtyku [Ice map of the Baltic]. Parameters of the operational ice chart and the ice code. Operational material: this page does not use it for decisions, only as a reference point.
IMGW-PIB: Mapa zlodzenia polskiego wybrzeża i Zalewu Wiślanego [Ice map of the Polish coast and the Vistula Lagoon]. Operational ice cartography. The file changes over time; always read the publication date.
Photograph of groynes in Zingst, 5 February 2012, author Mozzihh, Wikimedia Commons, licence CC BY-SA 4.0 (according to the V2 description). Image used in V2 · file page. The file page address was derived from the file name in V2 and has not been checked; the author, licence and date need confirmation. The photograph is not embedded on the page.

The Balticin winter.