geolimits document says,
Note
The geolimits function typically uses wider limits than the limits you specify to maintain the aspect ratio of the map.
The upper and lower limit would be changed for adjusting aspect ratio of map.
So, you need to specify Position of figure so that the map becomes a vertical rectangle.
matStr = load('rates.mat');
rates = matStr.rates1;
datetime = rates(:,1);
Latitude = rates(:,2);
Longitude = rates(:,3);
rates = rates(:,4);
figure("Position", [100 200 650 800]) % Added
gx = geoaxes;
geolimits([52.9569 80.0627], [0 45]);
geoplot(gx, Latitude, Longitude,'LineWidth', 4, 'color', 'k');
gx.LatitudeAxis.FontSize = 12;
gx.LatitudeAxis.Label.FontSize = 20;
gx.LatitudeAxis.Label.FontWeight = 'bold';
gx.LatitudeAxis.TickValues = [45 50 55 60 65 66.5 70 75 80];
gx.LatitudeAxis.TickLabels = {'45°N', '50°N', '55°N', '60°N', '65°N', 'Arctic Circle', '70°N', '75°N', '80°N'};
gx.LatitudeAxis.FontWeight = 'bold';
gx.LongitudeAxis.FontSize = 12;
gx.LongitudeAxis.Label.FontSize = 20;
gx.LongitudeAxis.Label.FontWeight = 'bold';
gx.LongitudeAxis.FontWeight = 'bold';
gx.LineWidth = .5;
gx.GridColor = 'k';
gx.GridAlpha = .5;
figure(1)
hold on
geobasemap('satellite')
colormap parula
c = colorbar;
c.FontSize = 12;
c.FontWeight = 'bold';
geoscatter(Latitude,Longitude, 25, rates, 'filled');
c.Label.String = 'data units)';
c.Label.FontWeight = 'bold';
c.Label.FontSize = 20;
c.Label.Rotation = 270;
c.Label.Position = [4.5 50 0];
hold off
o = 1;
