70

The problem is the increase in the rate of sea level rise. I pulled out some approximate numbers from the figure you presented: Can you see now how the sea level is rising much faster today than a century ago? Sea level rise, as well as climate change are normal things on Earth history. However, most times they happen at a very slow rate, allowing ...


33

The area is experiencing post-glacial isostatic rebound. Much of Canada was covered in an extensive ice sheet in the last glacial period (the 'Ice Age'), from about 110 ka until 12 ka. The ice in the Hudson Bay area was among the last to melt: A thick ice sheet depresses the crust (the lithosphere), making a small dent in the uppermost mantle (the ...


31

Using the latest numbers from the 2013 IPCC report (Ch. 4, the Cryosphere), Antarctica contains 58.3 m of sea level equivalent (sle) and Greenland 7.36 m sle. Remaining glaciers provide an additional 0.41 m sle. In total and adding very minor contributions from permafrost etc. the total comes out to approximately 66.1 m sle. EDIT: Just to be complete: If ...


26

There are lots of controls on sea level, not just the volume of water in the world ocean. These controls operate on different time and spatial scales, and interact in nonlinear ways. As a result, both global ('absolute') sea level and local ('relative') sea level can rise in some places and fall in others. For example, absolute sea-level is currently rising,...


25

The sea is not the only thing that rises, the sea floor can also rise and fall in accordance with the underlying geology. Oceanic tectonic plates sink as they age (and thus get colder and denser), the Solomon islands happen to be on a sinking section of the ocean floor and at the same time the sea level is rising. Keep in mind many of those islands have a ...


24

Sea level has a strong seasonal signal. The annual variability is less than the daily changes associated with tidal forcing in most locations, but still can be on the order of 5-10 cm (maximum values about 15 cm). The causes of the seasonal fluctuations are mostly associated with seasonal changes in wind intensity and patterns, changes in temperature that ...


21

Yes, there are lots of other factors. Factors affecting sea levels are no different from other natural processes: there is a large number of coupled, non-linear effects, operating on every time scale, and at every length scale, and across many orders of magnitude. The Wikipedia page Current sea level rise lists many of the known processes. And I wrote a ...


18

It would go down. In order to float, an object must displace a volume of fluid that weighs the same as the boat. In the case of a ship, this volume is less than the gross volume of the boat, including the air inside it. That's why it floats with the gunwales comfortably above the water. So when the boat is floating, it displaces some volume V, so relative ...


17

To my knowledge, the best study looking at potential explanations for the Red Sea crossing is the one by Nof and Paldor (1992). They present a couple of plausible scenarios for the crossing. The main one is the effect of strong winds blowing along the Gulf of Suez and they find that the sea level drop could be sufficient: It is found that, even for ...


16

The question is requesting an answer that has no practical application. So rather than improving on some hypothetical calculation, I will describe the problem and hopefully make the difficulty providing a real answer to a time frame clear. First: "polar ice" Antarctica is located in a polar position and consists of a multi-km thick ice sheet. The Arctic is ...


15

As Peter Jansson explains, sea level rise purely due to melting of land-based global ice works out "to approximately 66.1 m sle." An issue with respect to sea-level rise that isn't often mentioned (especially not in disaster movies!) is that thermal expansion of the sea - i.e. water expanding as global temperatures rise - will also have a huge effect: see ...


14

I don't know about the size of land masses, but their distribution and the shape of ocean basins definitely play a big role. When considering the ideal case of an all-ocean globe, i.e. one with no land masses (equilibrium tidal theory), the combined effect of sun and moon give a theoretical tidal range of less than 1 m(1). As tidal ranges can be much larger ...


14

Let's assume that the earth didn't suddenly stop spinning (because intertia and conservation of angular momentum would do all sorts of "interesting" things that are deserving of a What-If answer), and stipulate that the earth slowed down gradually, or possibly that it was never spinning in the first place (although I'm sure this would have all sorts of other ...


14

Because of post glacial rebound. The asthenosphere was pressed down under Laurentide ice sheet during last ice age and is now finding a new balance, without the weight of the ice. Note that around the ice sheet, the land is actually sinking today, like when ones partner gets up from a waterbed mattress.


13

To the best of our knowledge, sea-level is rising because the volume of water is increasing. There is substantial local variation in sea-level change; it's falling in some parts of Canada. But of the dozens of controls on local and global sea-level, the net effect is currently an average global rise of about 3 mm/y. It's not really 'a riddle'. The ...


13

The first part of the association is that increasing levels of greenhouse gases in the atmosphere will cause rising temperatures on earth. Here is some information on why that is so, if you are interested. Now assuming that temperatures are currently going up (they are), there are two mechanisms that will connect this to rising sea level, melting of ice on ...


12

Using the eTopo1 data Eakins and Sharman has calculated a hypsographic curve for the earth. In the elevation span between + 6 to -6 m they found that land area will change by 396 000 km2 per meter sea level change. In the range -7 to -51 m below current sea level the land area will change by 251 000 km2 per meter sea level. Thus to get an area the size of ...


12

Antarctica is the ice sheet (cap) that will contribute most IF it would melt completely. The 2013 IPCC report (Ch. 4, the Cryosphere) provides an estimate of 58.3 m of sea level equivalent (sle). Greenland would if completely wasted away provide 7.36 m sle. Remaining glaciers provide an additional 0.41 m sle. The likelihood of Antarctica completely wasting ...


12

The problem is that sea level is increasing faster than ever in last couple thousand years. It is currently rising at 3.2 mm/year according to satellite data: The curve you showed is not a straight line, it is rising at an increasing rate. And the trend is expected to continue: The last IPCC report (2018) on the subject say: Projections vary in the ...


12

Sea level rise from thermal expansion is a very slow process: oceans are 3.7 km deep on average, and water has a very large specific heat capacity. Here's a related diagram from the IPCC Third Assessment Report (page 17): Climate change didn't have much impact on the sea level, yet.


11

There are various plate tectonic models around, that are able to provide insight in paleobathymetry and -altimetry. These models include information on sea floor spreading and subduction, which provides much information on bathymetry. Also plate tectonic movement largely drives the uplift of mountain ranges, and combining this with isostatic effects of ...


11

There is some scope for continuing debate because quantifying the various components of the ice/snow/water balance are fraught with difficulty, and many of the estimates have error bounds which approach the magnitude that is being measured. However, a good best estimate, subject to continuing research, is given in:Is Antarctica losing or gaining ice? This ...


11

In a 1983 Journal of Geology paper by Milliman and Meade, "World-Wide Delivery of River Sediment to the Oceans" (link) it is estimated that the world's rivers carry about $13.5\times 10^9$ tonnes of sediment per year. If we assume an average density of $2.5~\rm{g/cm^3}$, this corresponds to a volume of 8.8 cubic kilometers. The total surface area of the ...


10

Can't say much about the later epochs, but the 'hellish Hadean' epoch without oceans is kind of an outdated idea. We have zircon records indicating that crust and oceanic formation was already done to some unknown extent 4.4 Gyrs ago. The zircon analyzed in the nature paper given originates from interaction with sub-crustal material in a watery environment ...


10

(I can't comment on @kaberett answer as a guest) Don't forget the odd effect that as ice melts and the water warms from 0C to 4C, that water will contract slightly, dropping sea level a bit (at least, locally). Once it gets above 4C, it will start expanding again. If the oceans overall cool a bit due to cold meltwater mixing in, they too will contract until ...


10

Don't rest so easy, ravenspoint. The Laurentide ice sheet at its maximum extent was larger than the Antarctic ice sheet is now. The bulk of that ice sheet melted in two pulses of 2000 years each, separated by the ~1000 year long Younger Dryas. During the first pulse, the Laurentide lost 5400 km3 of ice pear year. During the second pulse, it lost ice at an ...


10

In a recent study, Talone et al. (2014) compare 4 different geoids and evaluate their effects for oceanographic studies. The four geoids they used are: EGM96: The Earth Geopotential Model 1996 embodies ground-based as well as satellite measurements (Lemoine et al. 1998). Remotely sensed data were mainly radar altimeter observations, averaged and ...


10

It is "mean sea level above the Baltic Sea", in meters (source on page 109). That explains why it is used mainly in East-European countries. Martin Ekman - The Changing Level of the Baltic Sea during 300 Years - A clue to understanding the Earth shortly mentions some historical 'zero points' (page 111). As mentioned in the comments: mBf means méter ...


9

This is covered in an episode of the National Geographic TV series Aftermath called "When The Earth Stops Spinning". It's also covered by "If the Earth Stood Still: Modeling the absence of centrifugal force" by Witold Fraczek of Ersi, a GIS software company. The Earth is not round, but bulges at the equator. The diameter at the equator is 43km more than ...


9

Since this percentage is an area ratio, it fluctuates with sea level. Consequently it has fluctuated quite a few during the Phanerozoic (see Haq et al. 1988; Miller et al. 2005 for instance). Now if we're talking in term of oceanic/continental crust ratio, the present day continental crust age repartition shows that, by 2 Ga, ca. 60% of the present day ...


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