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| Fig. 1 SLC variation |
I. Introduction
Tide gauge stations have been measuring sea level change (SLC) around the world for centuries (Weekend Rebel Science Excursion - 54, Permanent Service for Mean Sea Level).
One relatively recent published paper details the complexities of SLC in terms of detecting SLC patterns ("On the robustness of predictions of sea level fingerprints", Mitrovica, et al. 2011).
SLC is a phenomenon where the change in sea level can be sea level rise (SLR) or sea level fall (SLF).
SLF is the part of SLC caused by a loss of gravity when ice melts or flows away from a large mass of ice like Greenland or a large glacial field like Glacier Bay, Alaska.
That loss of gravity will result in a release of seawater along coastlines near the ice sheet or large glacial field out to as much as 2,000 km.
That released seawater is relocated to other parts of the globe by the dynamics of the Earth's rotation, and other factors.
That relocation causes SLF around and about the coastlines of the land upon which the ice sheet or large glacial field is located, but it also causes SLR far away from the ice sheet or large glacial field where that relocated seawater finally ends up (Fig. 1; The Gravity of Sea Level Change, 2, 3, 4, 5; NASA Busts The Ghost).
General SLR on the other hand is caused by the addition of mass into the ocean when the ice sheet's or large glacial field's melt water or calved ice flows away from the large body of ice to be relocated and impact some tide gauge station far away.
Typically, to simplify these dynamics for an audience, scientists focus on only one source of the typical list of SLC generators such as Greenland, Antarctica, Glacier Bay, Svalbard, and Patagonia (Gre, Ant, Gla, Sva, and Pat).
To see why, try to imagine the cumulative effect of the three "as if" scenarios shown in Fig. 1.
By "as if" I mean it is an exercise of forgetting that all of them are melting, calving, and losing gravity at the same time, so considering them "as if" only one of them is causing SLC has limited analytical value.
Matters are made even more complex because in the main SLF is caused by events that take place nearer to a tide gauge station than SLR events do.
SLR causing events, in the main, take place further away from a tide gauge station than SLF causing events do.
The bottom line analysis to be conducted at any tide gauge station is to determine:
1) which ice sheets or large glacial fields caused SLC, andIn the final analysis they must all be considered together in order to obtain a robust SLC analysis, which is a cumulative event analysis.
2) how much SLC each ice sheet or large glacial field caused individually.
That is, to know the future conditions approaching any tide gauge station, one must know "the conditions" at the ice sheet(s) or large glacial field(s) which combined together influence SLC at that particular tide gauge station.
I call "the conditions" that influence SLC the "DNA" (Definitive Natural Attributes).
II. Definitive Natural Attributes
"Definitive natural attributes" are aspects of the dynamics which exert an inexorable influence on the sea level at a tide gauge station's location.
Like human DNA, the choice of what DNA to have is not determined either by the human or by the tide gauge.
It is determined, among other things, by the tide gauge's location (latitude & longitude) along with events that take place relatively close, in terms of SLF, but relatively distant in terms of SLR.
What happens in Greenland, Antarctica, Glacier Bay, Svalbard, and Patagonia (Gre, Ant, Gla, Sva, and Pat) is not in the control of a tide gauge station.
And by the same token those Cryosphere locations where the ice is do not control the global climate which causes those ice sheets and glacial fields to melt or not to melt (The Damaged Global Climate System, 2, 3, 4, 5, 6, 7).
The tide gauge stations around the globe can only record the sea level at any given time each and every day.
What ultimately determines the tide gauge's measured value itself is utterly outside the control of the tide gauge station's instrumentation.
This reality is akin to our human epigenetic realm (On the Origin of Cultural Epigenetics, On The Origin of Genieology, The Uncertain Gene, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 [especially 11]).
Furthermore, Anthropogenic damage to the climate system, as well as the global warming which results, is the epigenetic portion of SLC which the tide gauge stations will record for our research use.
And since human civilization's use of fossil fuels is the primary epigenetic factor that causes SLC, tide gauge stations are in effect measuring civilization's behavior.
For example, the Industrial Revolution's beginning is associated with the mid 18th century:
"... the term Industrial Revolution was first popularized by the English economic historian Arnold Toynbee (1852–83) to describe Britain’s economic development from 1760 to 1840."(Encyclopedia Britannica). Tide gauges have recorded the Anthropogenic impact of that revolution ever since (Proof of Concept - 5, Mysterious Zones of The Arctic - 5).
III. Supporting Appendices
There are three appendices added in support of today's post (Appendix A, Appendix B, Appendix C).
The appendices do not contain all seaports or all countries because this post is a focus on the DNA concept, not on all seaports or countries.
Those countries placed into the appendices are there because they have at least one tide gauge station and at least one seaport in a given WOD Zone.
A more complete (but not as refined) list of countries and seaports are in other Dredd Blog series posts (Countries With Sea Level Change - 2, Seaports With Sea Level Change - 2).
The term "WOD Zone" (in the appendices) means a numbered zone on the WOD Zone Map.
The term "Coastal Id" or "Coastline Code" (in the appendices) means a unique coastline area in a particular country as determined by the PSMSL.
About Appendix A
Appendix A contains this introduction:
"This is an appendix to: Beyond Fingerprints: Sea Level DNA - 4(Appendix A). That portion of the appendix informs you about the seaports and tide gauges of that country (including links to more port and tide gauge info).
Country Information for Argentina, Australia, China, Germany, and the USA follows in this appendix.
The data is divided by Country, Coastal Id, and WOD Zones, with three sections within each division:
1) a seaport data section (information about seaports)
2) a tide gauge data section (information about tide gauges)
3) a summary section (information about distances and SLC)
A single line separates the divisions in a country.
A double line separates countries."
The Summary Section of Appendix A has this format:
Summary for Argentina (Coastline Code: 860, WOD Zone: 5306):(Appendix A). This section of the appendix tells you about distances to ice sheets and large glacial fields that will determine the SLC DNA of that tide gauge location.
Distance to center of:
Svalbard: 13,980.6 km
Glacier Bay: 12,829.7 km
Greenland: 12,773.4 km
Antarctica: 5,679.06 km
Patagonia: 555.313 km
SLC: 1st yr (1957) 6,936.5 RLR --> final yr (1970) 7,029.32 RLR {+92.82 mm}
General DNA Analysis:
1) Patagonia & Antarctica have SLF influence,
2) Greenland adds more SLR than SLF,
3) Svalbard & Glacier Bay are SLR influences,
4) Some land level changes (LLC) effects may occur,
5) "Bathtub model" ice-mass-loss equivalent: 33,561 Gt,
6) Some ghost-water effects may occur (Ghost water loss: 25.0614 mm),
7) The bottom line is 92.82 mm of SLR.
About Appendix B
This appendix has "DNA Graphs (3-Line Format)" for each featured WOD Zone of each country set forth in Appendix A.
The three lines show the high, low, and actual sea level paths over the span of time that the tide gauges were in place.
About Appendix C
This appendix has "DNA Graphs (filled-in Format)" for each featured WOD Zone of each country also set forth in Appendix A.
The area between the high and low sea level range is filled in with solid blue color to emphasize the span or range of sea level variation while the tide gauges were in place recording SLC changes.
IV. Where To From Here?
The next thing is to look through the appendices that show seaport and tide gauge information about certain countries and certain seaports in those countries.
Then take a look at the graphs of sea level history in the two appendices (B & C) mentioned above.
These appendices show that, like human DNA, seaport SLC DNA is very individualistic and it varies enough that, closely studied, it can identify an individual seaport.
The major factors controlling DNA content are outside the human individual and also outside the geographical location of the seaport.
Less well understood is the fact that human DNA can change over time as environmental and other factors influence it (On The Origin of Genieology, Hypothesis: The Cultural Amygdala - 5).
Seaport SLC DNA also changes as environmental conditions in key locations (Gre, Ant, Gla, Sva, and Pat) change then cause changes in the tide gauge station's records.
V. The Future Problem
The multiple components that make up the DNA of SLC complicate predicting the future, in terms of sensing and/or calculating how the future SLC will compare to past SLC.
Will the Cryosphere follow a consistent path that matches the path of the past?
Or will there be acceleration caused by temperature increases and/or feedback loops?
Will each individual DNA component (Gre, Ant, Gla, Sva, and Pat) continue as it has in the past?
Two of the main "genes" in the SLC DNA construct have already changed significantly.
The main genes "Ant" (Antarctica) and "Gre" (Greenland) have gone through significant acceleration.
Note also that the SLC acceleration factors include change in Ocean Heat Content (OHC).
Notice how the change is increasing:
"Antarctica. The total mass loss from Antarctica increased from 40 ± 9 Gt/y in the 11-y time period 1979–1990 to 50 ± 14 Gt/y in 1989–2000, 166 ± 18 Gt/y in 1999–2009, and 252 ± 26 Gt/y in 2009–2017, that is, by a factor 6 (Fig. 2, Table 1, and SI Appendix, Fig. S1). This change in mass loss reflects an acceleration of 94 Gt/y per decade in 1979–2017, increasing from 48 Gt/y per decade in 1979–2001 to 134 Gt/y per decade in 2001–2017, or 280%.(Rignot et al., PNAS, 2019, emphasis added). Considering Greenland (Gre) does not ease the burden of paying attention to detail:
...
The mass loss ... is ... attributed to the intrusion of warm, salty, circumpolar deep water (CDW) on the continental shelf (35, 36), which vigorously melts the ice shelves, reduces buttressing of the glaciers, and allows them to flow faster.
...
Over the last four decades, the cumulative contribution to sea level from East Antarctica is not far behind that of West Antarctica, that is, East Antarctica is a major participant in the mass loss from Antarctica despite the recent, rapid mass loss from West Antarctica (Table 1). Our observations challenge the traditional view that the East Antarctic Ice Sheet is stable and immune to change. An immediate consequence is that closer attention should be paid to East Antarctica.
...
Our mass balance assessment ... suggests ... ice shelves may be exposed to CDW and could contribute multimeter SLR with unabated climate warming."
"In 2000–2012, half of the cumulative loss was from four glaciers ... Over 46 years, the conclusions are different ... This result illustrates the risk of summarizing the ice sheet loss on the basis of the fate of a few glaciers.(Greenland Ice Sheet, Mouginot, Rignot, et al. 2019, emphasis added). In other words, only comprehensive consideration produces robust results.
...
Using improved records of ice thickness, surface elevation, ice velocity, and SMB, we present a 46-years reconstruction of glacier changes across Greenland that reveals a dominance from ice discharge over the entire record and a sixfold increase in mass loss from the 1980s."
Thus, we see that these two DNA components (Gre, Ant) are complicated in the sense of analysts being able to properly derive a robust expectation of what tide gauge stations will be recording in the future.
That is, exactly how much and how fast SLC will take place is less certain than the fact that SLC is now, and will continue to take place in the future.
VI. Closing Comments
The scientists whose papers were quoted in today's post (Mouginot, Rignot, et al.) urged careful consideration of the defining natural attributes (DNA) that will determine the fate of seaports around the world.
I hear that!
The previous post in this series is here.
