The Changing Level of the Baltic Sea during 300 Years: A Clue to Understanding the Earth

158 Pages·2011·34.85 MB·English

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The Changing Level of the Baltic Sea
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during 300 Years:
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a A Clue to Understanding the Earth
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ThisisabookaboutthesealeveloftheBalticSea.Itmightseemasavery t
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specialized subject. In fact it is not, on the contrary. The fascinating thing e
isthatthissinglephysicalquantity–theBalticSealevel–tellsusalotabout B
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the planet we live on. The Baltic Sea has the world’s longest series of sea
l
t
levelobservations.FromtheBalticSealevel,asobservedduringthreecen- i
c
turies, we are able to draw conclusions about the behaviour of our Earth:
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its interior, its oceans, and its atmosphere. Thus, historical data from the e
a
BalticSeaareusedtosolvemodernEarthscienceproblemsofamoreglo-
d
balcharacter.Thisisthefundamentalideaofthebook. u
r
i
n
Moreover, the book gives a historical perspective on discoveries and solu-
g
tionsofthesealevelproblems.Thingsareexplainedbydescribinghowthey
3
haveactuallybeenfoundout(ornotfoundout),startingfromtheverybe- 0
0
ginning,sometimescommentingonoldresultsfromamodernpointofview.
Y
Originalscientificsourcesareusedthroughout.Thismeansthrowinglight e
a
alsoonimportantworksbeinglongsinceforgottenbymodernscientists. r
s
Finally, in order to broaden the outlook in somewhat unexpected direc-
tions,somespecialaspectsrelatedtothesealevelchangesareincludedat
theendofthebook. Martin Ekman
M
This book spans several Earth sciences, from solid geophysics through
a
oceanographytoclimatology.Itisintendedforreadingbyawiderangeof r
t
geoscientistsorotherpeoplewithaprofessionalinterestintheEarthand in
itschanges.Ihopeyouwillfindthebookinteresting. E
k
m
Summer Institute for Historical Geophysics
a
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Åland Islands
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The Changing Level of the Baltic Sea
during 300 Years:
A Clue to Understanding the Earth
Martin Ekman
Summer Institute forHistoricalGeophysics
Åland Islands
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SummerInstituteforHistoricalGeophysics,ÅlandIslands
TheSummerInstituteforHistoricalGeophysicsistheauthor’sone-man-
institute, performing research, issuing publications and now and then
giving lectures within the field of historical geophysics. For further in-
formation, or for access to publications in the series ”Small Publications
inHistoricalGeophysics”issuedbytheinstitute,goto:
www.historicalgeophysics.ax
©MartinEkman2009
ISBN978-952-92-5241-1
PrintingoriginalbyBenJohans,PQR
PrintedbyLogotipas
PublishedbytheSummerInstituteforHistoricalGeophysics,Äppelträd-
gårdenE,Haraldsby,AX–22410Godby,ÅlandIslands.Seealsoabove.
Coverpicture:TheStockholmsluice,wheresystematicsealevelobserva-
tionsstartedin1774.(PaintingbyAndersHolmin1780,CityMuseumof
Stockholm.)
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Contents
Preface 7
1. Introduction:WhatissointerestingabouttheBalticSealevel? 10
1.1 Remarkablephenomena 10
1.2 Remarkabledata 11
1.3 Theworld’slongestsealevelseries 16
1.4 Sealevelrelativetowhat? 19
2. Isthelandgoinguporthewatergoingdown? 21
2.1 Harbourproblemsandrelocationoftowns 21
2.2 Thescientificuseofsealrocks 24
2.3 Sealevelmarksandtheirsignificance 28
2.4 Thefirstlandupliftmap–onethatwasneverconstructed 31
3. PostglacialreboundandtheinterioroftheEarth 36
3.1 ThediscoveryoftheIceAge 36
3.2 Anewpossibility:Postglacialuplift? 37
3.3 Sealevelgauges:Upliftratesandthemarinelimit 39
3.4 TheviscosityoftheEarth’sinterior 43
3.5 Mareographs:Mappingtheupliftrate 47
3.6 Modellingthemantle,crustandiceoftheEarth 55
4. Climaticsealevelriseandtheglaciers 60
4.1 Thewaterlevelatthesluice:Achangeintherateof change? 60
4.2 Meltingglaciersandsealevelrise 61
4.3 Sealevelriseandglobalwarming 63
5. Wintersealevelchangesandtheatmosphere 69
5.1 Reversedcurrentsandthewater-works 69
5.2 Windsorairpressure? 71
5.3 Stormsandshort-termsealevelvariations 74
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5.4 Persistentwindsandlong-termsealevelvariations 78
5.5 Wintersandthevaryingseasonalsealevelvariation 84
5.6 Long-termsealevelandchangesofwinterclimate 85
5.7 Short-termsealevelandanotherchangeinwinterclimate 99
6. PoletidesandtherotationoftheEarth–andtheatmosphere
onceagain 102
6.1 Thediscoveryofpolarmotion 102
6.2 Thesearchforthepoletide–andthesurprisingresult 103
6.3 Polarmotionorwinds? 106
7. Meansealevelandtheseawateritself 110
7.1 Atwhatheightabovesealevelissealevel? 110
7.2 Meanseasurfacetopographyandsalinityoftheseawater 111
8. Somespecialeffects 118
8.1 Theworld’soldestpreservedsealevelgauge 118
8.2 Savingaparliamentfromthepostglacialuplift 120
8.3 HistoricalshorelevelsandVikingshipjetties 121
8.4 Sealevelandtheeconomyoftheroyalwatermills 121
8.5 Sealevelandthewinterthatneverarrived 122
Appendix:TheStockholmsealevelseries1774–2000 125
References(inchronologicalorder) 131
Index 146
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Preface
Thisisascientificbook spanning severalEarthsciences:fromsolidgeo-
physics through oceanography to climatology. Yet it is not an ordinary
scientificbook.Ithas,incertainrespects,asomewhatunusualcharacter.
First,thebookisspecializedandgeneralatoneandthesametime.What
we study here is just one quantity, the sea level of the Baltic Sea. From
this quantity, as observed during three centuries, we are able to draw
conclusions about the behaviour of our Earth as a whole: its interior, its
oceans, and its atmosphere. Thus, historical data from the Baltic Sea are
usedtosolvemodernEarthscienceproblemsofamoreglobalcharacter.
Thisisthefundamentalideaofthebook.
Second, the book gives a historical perspective on discoveries and solu-
tions of the sea level problems. Things are explained by describing how
they have actually been found out (or not found out), starting from the
very beginning, sometimes commenting on old results from a modern
pointofview.Originalscientificsourcesareusedthroughout.Thismeans
throwing light also on important works being long since forgotten by
modernscientists.
Third, in order to broaden the outlook in somewhat unexpected direc-
tions,somespecialaspectsrelatedtothesealevelchangesareincludedat
theendofthebook.
Thebookisintendedforreadingbyawiderangeofgeoscientistsorother
peoplewithaprofessionalinterestintheEarthanditschanges.Therea-
derisassumedtohaveanelementaryknowledgeofbasicEarthscience,
but not to know anything about sea level problems. The reading of the
bookwillbefacilitatedbyunderstandingnature’sownlanguage,mathe-
matics, at the level of a novice at a university. In some cases more ad-
vanced mathematical concepts occur in the text; these can simply be
passed over by those who are not familiar with them. The book might
alsobeofinterestforhistoriansofscience,buttheyshouldbeawarethat
thisisabookaboutscienceratherthanabouthistoryofscience.
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There are a number of quotations in the text, serving to illustrate and
bring to life important points in the scientific development. Their trans-
lationsintoEnglishareduetothepresentauthor.Someoftheolderquo-
tations have had to be translated rather freely to make them readable;
however, great care has always been taken to convey the original mes-
sageinacorrectway.
Referencesinthetextaregivenbynamesandyearswithinbrackets;when
yearsoccurwithoutbracketstheyrelatetohistoricalinformation.Inorder
tomakethescientistsandotherpersonsreferredtolessanonymous,they
have all been given a brief characterization, such as British oceanogra-
pher and climatologist, German-Swedish harbour engineer etc. The ref-
erence list at the end is not ordered alphabetically, as would be normal,
but chronologically. This has made it possible to give a chronological
overviewofallthepublishedworksused.
Most of the author’s own research included here has been performed
withinhisprivateone-man-institute,theSummerInstituteforHistorical
Geophysics,ontheÅlandIslandsintheBalticSea.Somepartsoftheearly
research have been made while the author was working at the Geodetic
ResearchDivisionoftheNationalLandSurveyofSweden.
A number of people have been helpful during the work with this book
and the research leading up to it. I would like to thank the persons who
have read the manuscript and given constructive comments on it: Kurt
Lambeck at the Research School of Earth Sciences at the Australian Na-
tionalUniversity,JaakkoMäkinenattheFinnishGeodeticInstitute,An-
ders Stigebrandt at the Oceanographic Department at the Göteborg
University in Sweden, and Philip Woodworth at the Permanent Service
forMeanSeaLevelinGreatBritain.TofindtheoldliteratureIhavehad
great benefit of the library of the Royal Swedish Academy of Sciences,
partly deposited with the University Library of Stockholm, and also of
the University Library of Uppsala and the library of the former Geo-
graphical Survey Office of Sweden. To find original sea level data not
published I had, in earlier stages of the work, great use of the City
ArchivesofStockholm,andalsooftheDanishNationalArchivesandthe
archivesoftheSwedishMeteorologicalandHydrologicalInstitute.
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My final thanks go to those sea level observers, long since dead, whose
faithful work in former centuries at sluices, light-houses, harbours and
scientificinstitutionshasmadethisbookpossible.
ÅlandIslands,attheseashore,midsummer2008
MartinEkman