Data
of Core Angular Momentum Changes
Author(s):
Andrew Jackson(1), Jeremy Bloxham(2) & David
Gubbins(1)
Affiliation:
(1) Dept Earth Sciences, Leeds University
(2) Dept Earth and Planetary Sciences, Harvard
University
Sampling
time interval :
1 year
Time
span from 1840.0 to 1990.0
Data
unit :
Excess length of day in milliseconds
over standard day of 86400 seconds
Modelling
hypotheses:
The
zonal toroidal t_1^0 and t_3^0
components of a fully time-dependent geostrophic flow constructed under
the frozen flux hypothesis are used to estimate the
core angular momentum (CAM) using the hypothesis of Jault Gire and LeMouel
(1988). The flow is constructed using a basis of B-splines with knot spacing of 2.5 years. The CAM is then transformed into an
equivalent change in the length of the day as seen on the solid Earth by conservation of angular momentum. The predictions only
give relative changes in the lod, therefore an arbitrary offset should
be chosen in order that the predictions agree reasonably well with the lod series
from astronomical observations. A value of 3.25 milliseconds has been added to the predictions to give the values
presented here. Three different series are given rough, intermediate and smooth - they have different misfits to
the magnetic data. The smooth model is the preferred one.
Description
of the data used for model computation : The
magnetic field and its rate of change at the core-mantle interface was computed
at 2.5 year intervals from
field model ufm1 of Bloxham & Jackson (1992) References
to be mentioned when data are used: Jackson
A., 1997. Time-Depency
of geostrophic core surface motions,
Phys. Earth Planet. Int., 103, pp 293-311.
Related
references: Bloxham
J. & Jackson A., 1992. Time-dependent
mapping of the magnetic field at the core-mantle boundary,
J.
Geophys. Res., 97, pp 19537-19563. rough 1840 2.46337 1841 1.59971 1842 1.66112 1843 1.85855 1844 1.85453 1845 1.76316 1846 1.6954 1847 1.67109 1848 1.68664 1849 1.72402 1850 1.7507 1851 1.74309 1852 1.71581 1853 1.69246 1854 1.68393 1855 1.68837 1856 1.7048 1857 1.73795 1858 1.79353 1859 1.86687 1860 1.94298 1861 2.01069 1862 2.07606 1863 2.14934 1864 2.23803 1865 2.34687 1866 2.47401 1867 2.59174 1868 2.66729 1869 2.69979 1870 2.72034 1871 2.75327 1872 2.79038 1873 2.81571 1874 2.82196 1875 2.81052 1876 2.78664 1877 2.76956 1878 2.78083 1879 2.81418 1880 2.83556 1881 2.82436 1882 2.81857 1883 2.86776 1884 2.95156 1885 2.97957 1886 2.88998 1887 2.7473 1888 2.64296 1889 2.56149 1890 2.38052 1891 2.0269 1892 1.64296 1893 1.41757 1894 1.37037 1895 1.35177 1896 1.25587 1897 1.18085 1898 1.26894 1899 1.50132 1900 1.69817 1901 1.72289 1902 1.6398 1903 1.55854 1904 1.47574 1905 1.27496 1906 0.882367 1907 0.414104 1908 0.027203 1909 -0.272981 1910 -0.63278 1911 -1.14298 1912 -1.64579 1913 -1.93036 1914 -1.99401 1915 -2.04229 1916 -2.22489 1917 -2.43201 1918 -2.49618 1919 -2.41713 1920 -2.36169 1921 -2.44349 1922 -2.53424 1923 -2.45394 1924 -2.2242 1925 -2.06827 1926 -2.1514 1927 -2.37188 1928 -2.56669 1929 -2.69745 1930 -2.85046 1931 -3.08067 1932 -3.29596 1933 -3.37399 1934 -3.34321 1935 -3.38286 1936 -3.60893 1937 -3.85819 1938 -3.90718 1939 -3.75216 1940 -3.60917 1941 -3.63013 1942 -3.67232 1943 -3.52842 1944 -3.19888 1945 -2.89197 1946 -2.75971 1947 -2.69315 1948 -2.52442 1949 -2.23221 1950 -1.94171 1951 -1.75829 1952 -1.68243 1953 -1.68773 1954 -1.73173 1955 -1.75599 1956 -1.7083 1957 -1.5643 1958 -1.30901 1959 -0.982692 1960 -0.680824 1961 -0.467334 1962 -0.270274 1963 0.011894 1964 0.379994 1965 0.734129 1966 0.99621 1967 1.19287 1968 1.37597 1969 1.57523 1970 1.79826 1971 2.03835 1972 2.23536 1973 2.31871 1974 2.28463 1975 2.19623 1976 2.10817 1977 2.02991 1978 1.96056 1979 1.92166 1980 1.95721 1981 2.08512 1982 2.21506 1983 2.23394 1984 2.12748 1985 1.98021 1986 1.85411 1987 1.70362 1988 1.47187 1989 1.45941 1990 2.32423 intermediate 1840 -0.965637 1841 -2.97081 1842 -2.72437 1843 -2.24464 1844 -2.33016 1845 -2.55966 1846 -2.56969 1847 -2.43998 1848 -2.35507 1849 -2.36119 1850 -2.36624 1851 -2.29912 1852 -2.19678 1853 -2.12086 1854 -2.07989 1855 -2.02927 1856 -1.9347 1857 -1.81244 1858 -1.69042 1859 -1.57496 1860 -1.4508 1861 -1.30731 1862 -1.15636 1863 -1.01474 1864 -0.884127 1865 -0.751015 1866 -0.606211 1867 -0.46033 1868 -0.328577 1869 -0.217792 1870 -0.126457 1871 -0.049453 1872 0.031261 1873 0.136088 1874 0.265263 1875 0.398858 1876 0.521782 1877 0.64181 1878 0.772096 1879 0.917982 1880 1.077 1881 1.24628 1882 1.42268 1883 1.60262 1884 1.77423 1885 1.9173 1886 2.01596 1887 2.07314 1888 2.0964 1889 2.09284 1890 2.06904 1891 2.03122 1892 1.9842 1893 1.933 1894 1.89548 1895 1.90235 1896 1.97631 1897 2.10587 1898 2.27097 1899 2.45137 1900 2.62667 1901 2.7731 1902 2.85342 1903 2.82886 1904 2.70239 1905 2.51873 1906 2.31282 1907 2.07333 1908 1.77872 1909 1.43954 1910 1.09845 1911 0.791184 1912 0.520324 1913 0.280438 1914 0.072767 1915 -0.094766 1916 -0.221233 1917 -0.334817 1918 -0.469994 1919 -0.638489 1920 -0.829275 1921 -1.02382 1922 -1.17749 1923 -1.24176 1924 -1.22786 1925 -1.20678 1926 -1.23887 1927 -1.33133 1928 -1.47677 1929 -1.63646 1930 -1.74042 1931 -1.73395 1932 -1.6292 1933 -1.45636 1934 -1.2778 1935 -1.18798 1936 -1.24487 1937 -1.35481 1938 -1.391 1939 -1.33626 1940 -1.28306 1941 -1.29658 1942 -1.31384 1943 -1.24418 1944 -1.09648 1945 -0.979189 1946 -0.973149 1947 -1.03136 1948 -1.07676 1949 -1.07588 1950 -1.03887 1951 -0.987105 1952 -0.979384 1953 -1.0801 1954 -1.26721 1955 -1.43221 1956 -1.48755 1957 -1.44445 1958 -1.33891 1959 -1.20807 1960 -1.0903 1961 -1.00456 1962 -0.892044 1963 -0.678066 1964 -0.369146 1965 -0.053029 1966 0.198568 1967 0.392188 1968 0.55379 1969 0.706062 1970 0.868426 1971 1.04673 1972 1.19314 1973 1.24827 1974 1.19637 1975 1.06527 1976 0.887784 1977 0.708869 1978 0.575936 1979 0.522317 1980 0.567269 1981 0.703109 1982 0.81684 1983 0.775039 1984 0.580027 1985 0.369868 1986 0.237644 1987 0.072889 1988 -0.263152 1989 -0.389575 1990 0.594186 smooth preferred one 1840 0.42635 1841 -0.738686 1842 -0.579399 1843 -0.289181 1844 -0.342795 1845 -0.496371 1846 -0.536269 1847 -0.494744 1848 -0.462617 1849 -0.46383 1850 -0.455443 1851 -0.405918 1852 -0.340939 1853 -0.298852 1854 -0.280136 1855 -0.247405 1856 -0.172367 1857 -0.069682 1858 0.035929 1859 0.135417 1860 0.235396 1861 0.341662 1862 0.454011 1863 0.570754 1864 0.690576 1865 0.812539 1866 0.935128 1867 1.05448 1868 1.16603 1869 1.26295 1870 1.33614 1871 1.38376 1872 1.43349 1873 1.51868 1874 1.63417 1875 1.73622 1876 1.7936 1877 1.83159 1878 1.88832 1879 1.97143 1880 2.05808 1881 2.13031 1882 2.19491 1883 2.26419 1884 2.3344 1885 2.38578 1886 2.40224 1887 2.3852 1888 2.34019 1889 2.26662 1890 2.15778 1891 2.01388 1892 1.86382 1893 1.74295 1894 1.66868 1895 1.64049 1896 1.65712 1897 1.7174 1898 1.8195 1899 1.94637 1900 2.06577 1901 2.14581 1902 2.15891 1903 2.07947 1904 1.90454 1905 1.65379 1906 1.34562 1907 0.98962 1908 0.593292 1909 0.167545 1910 -0.273313 1911 -0.709414 1912 -1.09923 1913 -1.39758 1914 -1.5998 1915 -1.74177 1916 -1.85341 1917 -1.93391 1918 -1.97573 1919 -1.99351 1920 -2.02409 1921 -2.08663 1922 -2.12569 1923 -2.07095 1924 -1.93862 1925 -1.83141 1926 -1.83253 1927 -1.93217 1928 -2.09693 1929 -2.28697 1930 -2.45593 1931 -2.5634 1932 -2.59388 1933 -2.54046 1934 -2.45178 1935 -2.43197 1936 -2.545 1937 -2.68449 1938 -2.70723 1939 -2.60202 1940 -2.48966 1941 -2.45828 1942 -2.44253 1943 -2.34279 1944 -2.1548 1945 -1.96965 1946 -1.85679 1947 -1.78246 1948 -1.68903 1949 -1.56243 1950 -1.43215 1951 -1.33072 1952 -1.29521 1953 -1.36096 1954 -1.4974 1955 -1.60808 1956 -1.61222 1957 -1.50326 1958 -1.29441 1959 -1.02695 1960 -0.770243 1961 -0.569498 1962 -0.368392 1963 -0.088605 1964 0.270407 1965 0.63141 1966 0.931386 1967 1.17771 1968 1.39526 1969 1.60682 1970 1.8331 1971 2.07949 1972 2.29042 1973 2.39759 1974 2.38938 1975 2.31083 1976 2.20543 1977 2.10045 1978 2.01907 1979 1.98247 1980 2.0099 1981 2.10175 1982 2.18328 1983 2.16422 1984 2.02972 1985 1.84027 1986 1.64231 1987 1.41287 1988 1.12532 1989 1.06866 1990 1.84749 If you prefer this table converted to ASCII, click here