= Solution
Use a common emission time $t_0$ and a path length $L$, and treat each observed period as a narrow <wave packet>. For <deep-water gravity waves>, its <group velocity> is $gT/(4\pi)$, not the <phase velocity> $gT/(2\pi)$. Therefore the <dispersive swell source inversion> gives
$$
t-t_0=\frac{4\pi L}{gT}=\frac{C}{T},\qquad
\boxed{T(t)=\frac{C}{t-t_0},\quad \frac{dT}{dt}=-\frac{T^2}{C}.}
$$
Thus period decreases hyperbolically, while frequency $1/T$ increases linearly. The elapsed time between the two observations is $40\,\mathrm h\,40\,\mathrm{min}=146400\,\mathrm s$, so
$$
C=\frac{146400}{1/14-1/30}=3.8430\times10^6\,\mathrm{s^2},
\qquad
\boxed{L=\frac{gC}{4\pi}=3.00\times10^6\,\mathrm m.}
$$
The frequency slope is $2.6021\times10^{-7}\,\mathrm{Hz\,s^{-1}}$. Initially $dT/dt=-0.843\,\mathrm{s\,h^{-1}}$; at 14 s it has slowed to $-0.184\,\mathrm{s\,h^{-1}}$. The inferred emission was $C/30=35\,\mathrm h\,35\,\mathrm{min}$ before the first arrival, namely \b[19 March at 1710 UT]. Both observed endpoints give this same time.
A northward-propagating swell with this distance scale points to a remote energetic storm south of the high Arctic rather than local wind acting on continuous <sea ice>. Along a meridional route, 3,000 km is about $27^\circ$ of latitude, putting the source on the scale of the northern North Atlantic and adjacent open seas. A route through Fram Strait is plausible, but longitude and refraction are not supplied, so no particular storm or unique source position follows. Long swell arriving first and steadily increasing frequency are the expected signatures of remote <wave dispersion>. The distance and time are conditional on an approximately impulsive source and open-water propagation speeds; passage through ice, currents and finite storm duration produce corrections.
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